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freebsd-skq/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
avg 9e3a16fd34 MFV r316929: 6914 kernel virtual memory fragmentation leads to hang 
illumos/illumos-gate@af868f46a5
af868f46a5

https://www.illumos.org/issues/6914

FreeBSD note: only a ZFS part of the change is merged, changes to the VM
subsystem are not ported (obviously).  Also, now that FreeBSD has
vmem(9) we don't have to ifdef-out the code that uses it.

MFC after:	2 weeks
2017-05-26 11:23:16 +00:00

7733 lines
231 KiB
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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012, Joyent, Inc. All rights reserved.
* Copyright (c) 2011, 2017 by Delphix. All rights reserved.
* Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
* Copyright 2015 Nexenta Systems, Inc. All rights reserved.
*/
/*
* DVA-based Adjustable Replacement Cache
*
* While much of the theory of operation used here is
* based on the self-tuning, low overhead replacement cache
* presented by Megiddo and Modha at FAST 2003, there are some
* significant differences:
*
* 1. The Megiddo and Modha model assumes any page is evictable.
* Pages in its cache cannot be "locked" into memory. This makes
* the eviction algorithm simple: evict the last page in the list.
* This also make the performance characteristics easy to reason
* about. Our cache is not so simple. At any given moment, some
* subset of the blocks in the cache are un-evictable because we
* have handed out a reference to them. Blocks are only evictable
* when there are no external references active. This makes
* eviction far more problematic: we choose to evict the evictable
* blocks that are the "lowest" in the list.
*
* There are times when it is not possible to evict the requested
* space. In these circumstances we are unable to adjust the cache
* size. To prevent the cache growing unbounded at these times we
* implement a "cache throttle" that slows the flow of new data
* into the cache until we can make space available.
*
* 2. The Megiddo and Modha model assumes a fixed cache size.
* Pages are evicted when the cache is full and there is a cache
* miss. Our model has a variable sized cache. It grows with
* high use, but also tries to react to memory pressure from the
* operating system: decreasing its size when system memory is
* tight.
*
* 3. The Megiddo and Modha model assumes a fixed page size. All
* elements of the cache are therefore exactly the same size. So
* when adjusting the cache size following a cache miss, its simply
* a matter of choosing a single page to evict. In our model, we
* have variable sized cache blocks (rangeing from 512 bytes to
* 128K bytes). We therefore choose a set of blocks to evict to make
* space for a cache miss that approximates as closely as possible
* the space used by the new block.
*
* See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
* by N. Megiddo & D. Modha, FAST 2003
*/
/*
* The locking model:
*
* A new reference to a cache buffer can be obtained in two
* ways: 1) via a hash table lookup using the DVA as a key,
* or 2) via one of the ARC lists. The arc_read() interface
* uses method 1, while the internal ARC algorithms for
* adjusting the cache use method 2. We therefore provide two
* types of locks: 1) the hash table lock array, and 2) the
* ARC list locks.
*
* Buffers do not have their own mutexes, rather they rely on the
* hash table mutexes for the bulk of their protection (i.e. most
* fields in the arc_buf_hdr_t are protected by these mutexes).
*
* buf_hash_find() returns the appropriate mutex (held) when it
* locates the requested buffer in the hash table. It returns
* NULL for the mutex if the buffer was not in the table.
*
* buf_hash_remove() expects the appropriate hash mutex to be
* already held before it is invoked.
*
* Each ARC state also has a mutex which is used to protect the
* buffer list associated with the state. When attempting to
* obtain a hash table lock while holding an ARC list lock you
* must use: mutex_tryenter() to avoid deadlock. Also note that
* the active state mutex must be held before the ghost state mutex.
*
* Note that the majority of the performance stats are manipulated
* with atomic operations.
*
* The L2ARC uses the l2ad_mtx on each vdev for the following:
*
* - L2ARC buflist creation
* - L2ARC buflist eviction
* - L2ARC write completion, which walks L2ARC buflists
* - ARC header destruction, as it removes from L2ARC buflists
* - ARC header release, as it removes from L2ARC buflists
*/
/*
* ARC operation:
*
* Every block that is in the ARC is tracked by an arc_buf_hdr_t structure.
* This structure can point either to a block that is still in the cache or to
* one that is only accessible in an L2 ARC device, or it can provide
* information about a block that was recently evicted. If a block is
* only accessible in the L2ARC, then the arc_buf_hdr_t only has enough
* information to retrieve it from the L2ARC device. This information is
* stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block
* that is in this state cannot access the data directly.
*
* Blocks that are actively being referenced or have not been evicted
* are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within
* the arc_buf_hdr_t that will point to the data block in memory. A block can
* only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC
* caches data in two ways -- in a list of ARC buffers (arc_buf_t) and
* also in the arc_buf_hdr_t's private physical data block pointer (b_pdata).
*
* The L1ARC's data pointer may or may not be uncompressed. The ARC has the
* ability to store the physical data (b_pdata) associated with the DVA of the
* arc_buf_hdr_t. Since the b_pdata is a copy of the on-disk physical block,
* it will match its on-disk compression characteristics. This behavior can be
* disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the
* compressed ARC functionality is disabled, the b_pdata will point to an
* uncompressed version of the on-disk data.
*
* Data in the L1ARC is not accessed by consumers of the ARC directly. Each
* arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it.
* Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC
* consumer. The ARC will provide references to this data and will keep it
* cached until it is no longer in use. The ARC caches only the L1ARC's physical
* data block and will evict any arc_buf_t that is no longer referenced. The
* amount of memory consumed by the arc_buf_ts' data buffers can be seen via the
* "overhead_size" kstat.
*
* Depending on the consumer, an arc_buf_t can be requested in uncompressed or
* compressed form. The typical case is that consumers will want uncompressed
* data, and when that happens a new data buffer is allocated where the data is
* decompressed for them to use. Currently the only consumer who wants
* compressed arc_buf_t's is "zfs send", when it streams data exactly as it
* exists on disk. When this happens, the arc_buf_t's data buffer is shared
* with the arc_buf_hdr_t.
*
* Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The
* first one is owned by a compressed send consumer (and therefore references
* the same compressed data buffer as the arc_buf_hdr_t) and the second could be
* used by any other consumer (and has its own uncompressed copy of the data
* buffer).
*
* arc_buf_hdr_t
* +-----------+
* | fields |
* | common to |
* | L1- and |
* | L2ARC |
* +-----------+
* | l2arc_buf_hdr_t
* | |
* +-----------+
* | l1arc_buf_hdr_t
* | | arc_buf_t
* | b_buf +------------>+-----------+ arc_buf_t
* | b_pdata +-+ |b_next +---->+-----------+
* +-----------+ | |-----------| |b_next +-->NULL
* | |b_comp = T | +-----------+
* | |b_data +-+ |b_comp = F |
* | +-----------+ | |b_data +-+
* +->+------+ | +-----------+ |
* compressed | | | |
* data | |<--------------+ | uncompressed
* +------+ compressed, | data
* shared +-->+------+
* data | |
* | |
* +------+
*
* When a consumer reads a block, the ARC must first look to see if the
* arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new
* arc_buf_t and either copies uncompressed data into a new data buffer from an
* existing uncompressed arc_buf_t, decompresses the hdr's b_pdata buffer into a
* new data buffer, or shares the hdr's b_pdata buffer, depending on whether the
* hdr is compressed and the desired compression characteristics of the
* arc_buf_t consumer. If the arc_buf_t ends up sharing data with the
* arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be
* the last buffer in the hdr's b_buf list, however a shared compressed buf can
* be anywhere in the hdr's list.
*
* The diagram below shows an example of an uncompressed ARC hdr that is
* sharing its data with an arc_buf_t (note that the shared uncompressed buf is
* the last element in the buf list):
*
* arc_buf_hdr_t
* +-----------+
* | |
* | |
* | |
* +-----------+
* l2arc_buf_hdr_t| |
* | |
* +-----------+
* l1arc_buf_hdr_t| |
* | | arc_buf_t (shared)
* | b_buf +------------>+---------+ arc_buf_t
* | | |b_next +---->+---------+
* | b_pdata +-+ |---------| |b_next +-->NULL
* +-----------+ | | | +---------+
* | |b_data +-+ | |
* | +---------+ | |b_data +-+
* +->+------+ | +---------+ |
* | | | |
* uncompressed | | | |
* data +------+ | |
* ^ +->+------+ |
* | uncompressed | | |
* | data | | |
* | +------+ |
* +---------------------------------+
*
* Writing to the ARC requires that the ARC first discard the hdr's b_pdata
* since the physical block is about to be rewritten. The new data contents
* will be contained in the arc_buf_t. As the I/O pipeline performs the write,
* it may compress the data before writing it to disk. The ARC will be called
* with the transformed data and will bcopy the transformed on-disk block into
* a newly allocated b_pdata. Writes are always done into buffers which have
* either been loaned (and hence are new and don't have other readers) or
* buffers which have been released (and hence have their own hdr, if there
* were originally other readers of the buf's original hdr). This ensures that
* the ARC only needs to update a single buf and its hdr after a write occurs.
*
* When the L2ARC is in use, it will also take advantage of the b_pdata. The
* L2ARC will always write the contents of b_pdata to the L2ARC. This means
* that when compressed ARC is enabled that the L2ARC blocks are identical
* to the on-disk block in the main data pool. This provides a significant
* advantage since the ARC can leverage the bp's checksum when reading from the
* L2ARC to determine if the contents are valid. However, if the compressed
* ARC is disabled, then the L2ARC's block must be transformed to look
* like the physical block in the main data pool before comparing the
* checksum and determining its validity.
*/
#include <sys/spa.h>
#include <sys/zio.h>
#include <sys/spa_impl.h>
#include <sys/zio_compress.h>
#include <sys/zio_checksum.h>
#include <sys/zfs_context.h>
#include <sys/arc.h>
#include <sys/refcount.h>
#include <sys/vdev.h>
#include <sys/vdev_impl.h>
#include <sys/dsl_pool.h>
#include <sys/multilist.h>
#ifdef _KERNEL
#include <sys/dnlc.h>
#include <sys/racct.h>
#endif
#include <sys/callb.h>
#include <sys/kstat.h>
#include <sys/trim_map.h>
#include <zfs_fletcher.h>
#include <sys/sdt.h>
#include <machine/vmparam.h>
#ifdef illumos
#ifndef _KERNEL
/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
boolean_t arc_watch = B_FALSE;
int arc_procfd;
#endif
#endif /* illumos */
static kmutex_t arc_reclaim_lock;
static kcondvar_t arc_reclaim_thread_cv;
static boolean_t arc_reclaim_thread_exit;
static kcondvar_t arc_reclaim_waiters_cv;
static kmutex_t arc_dnlc_evicts_lock;
static kcondvar_t arc_dnlc_evicts_cv;
static boolean_t arc_dnlc_evicts_thread_exit;
uint_t arc_reduce_dnlc_percent = 3;
/*
* The number of headers to evict in arc_evict_state_impl() before
* dropping the sublist lock and evicting from another sublist. A lower
* value means we're more likely to evict the "correct" header (i.e. the
* oldest header in the arc state), but comes with higher overhead
* (i.e. more invocations of arc_evict_state_impl()).
*/
int zfs_arc_evict_batch_limit = 10;
/* number of seconds before growing cache again */
static int arc_grow_retry = 60;
/* shift of arc_c for calculating overflow limit in arc_get_data_buf */
int zfs_arc_overflow_shift = 8;
/* shift of arc_c for calculating both min and max arc_p */
static int arc_p_min_shift = 4;
/* log2(fraction of arc to reclaim) */
static int arc_shrink_shift = 7;
/*
* log2(fraction of ARC which must be free to allow growing).
* I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
* when reading a new block into the ARC, we will evict an equal-sized block
* from the ARC.
*
* This must be less than arc_shrink_shift, so that when we shrink the ARC,
* we will still not allow it to grow.
*/
int arc_no_grow_shift = 5;
/*
* minimum lifespan of a prefetch block in clock ticks
* (initialized in arc_init())
*/
static int arc_min_prefetch_lifespan;
/*
* If this percent of memory is free, don't throttle.
*/
int arc_lotsfree_percent = 10;
static int arc_dead;
extern boolean_t zfs_prefetch_disable;
/*
* The arc has filled available memory and has now warmed up.
*/
static boolean_t arc_warm;
/*
* These tunables are for performance analysis.
*/
uint64_t zfs_arc_max;
uint64_t zfs_arc_min;
uint64_t zfs_arc_meta_limit = 0;
uint64_t zfs_arc_meta_min = 0;
int zfs_arc_grow_retry = 0;
int zfs_arc_shrink_shift = 0;
int zfs_arc_p_min_shift = 0;
uint64_t zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
u_int zfs_arc_free_target = 0;
/* Absolute min for arc min / max is 16MB. */
static uint64_t arc_abs_min = 16 << 20;
boolean_t zfs_compressed_arc_enabled = B_TRUE;
static int sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS);
static int sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS);
static int sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS);
static int sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS);
#if defined(__FreeBSD__) && defined(_KERNEL)
static void
arc_free_target_init(void *unused __unused)
{
zfs_arc_free_target = vm_pageout_wakeup_thresh;
}
SYSINIT(arc_free_target_init, SI_SUB_KTHREAD_PAGE, SI_ORDER_ANY,
arc_free_target_init, NULL);
TUNABLE_QUAD("vfs.zfs.arc_meta_limit", &zfs_arc_meta_limit);
TUNABLE_QUAD("vfs.zfs.arc_meta_min", &zfs_arc_meta_min);
TUNABLE_INT("vfs.zfs.arc_shrink_shift", &zfs_arc_shrink_shift);
SYSCTL_DECL(_vfs_zfs);
SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_max, CTLTYPE_U64 | CTLFLAG_RWTUN,
0, sizeof(uint64_t), sysctl_vfs_zfs_arc_max, "QU", "Maximum ARC size");
SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_min, CTLTYPE_U64 | CTLFLAG_RWTUN,
0, sizeof(uint64_t), sysctl_vfs_zfs_arc_min, "QU", "Minimum ARC size");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, arc_average_blocksize, CTLFLAG_RDTUN,
&zfs_arc_average_blocksize, 0,
"ARC average blocksize");
SYSCTL_INT(_vfs_zfs, OID_AUTO, arc_shrink_shift, CTLFLAG_RW,
&arc_shrink_shift, 0,
"log2(fraction of arc to reclaim)");
SYSCTL_INT(_vfs_zfs, OID_AUTO, compressed_arc_enabled, CTLFLAG_RDTUN,
&zfs_compressed_arc_enabled, 0, "Enable compressed ARC");
/*
* We don't have a tunable for arc_free_target due to the dependency on
* pagedaemon initialisation.
*/
SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_free_target,
CTLTYPE_UINT | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(u_int),
sysctl_vfs_zfs_arc_free_target, "IU",
"Desired number of free pages below which ARC triggers reclaim");
static int
sysctl_vfs_zfs_arc_free_target(SYSCTL_HANDLER_ARGS)
{
u_int val;
int err;
val = zfs_arc_free_target;
err = sysctl_handle_int(oidp, &val, 0, req);
if (err != 0 || req->newptr == NULL)
return (err);
if (val < minfree)
return (EINVAL);
if (val > vm_cnt.v_page_count)
return (EINVAL);
zfs_arc_free_target = val;
return (0);
}
/*
* Must be declared here, before the definition of corresponding kstat
* macro which uses the same names will confuse the compiler.
*/
SYSCTL_PROC(_vfs_zfs, OID_AUTO, arc_meta_limit,
CTLTYPE_U64 | CTLFLAG_MPSAFE | CTLFLAG_RW, 0, sizeof(uint64_t),
sysctl_vfs_zfs_arc_meta_limit, "QU",
"ARC metadata limit");
#endif
/*
* Note that buffers can be in one of 6 states:
* ARC_anon - anonymous (discussed below)
* ARC_mru - recently used, currently cached
* ARC_mru_ghost - recentely used, no longer in cache
* ARC_mfu - frequently used, currently cached
* ARC_mfu_ghost - frequently used, no longer in cache
* ARC_l2c_only - exists in L2ARC but not other states
* When there are no active references to the buffer, they are
* are linked onto a list in one of these arc states. These are
* the only buffers that can be evicted or deleted. Within each
* state there are multiple lists, one for meta-data and one for
* non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
* etc.) is tracked separately so that it can be managed more
* explicitly: favored over data, limited explicitly.
*
* Anonymous buffers are buffers that are not associated with
* a DVA. These are buffers that hold dirty block copies
* before they are written to stable storage. By definition,
* they are "ref'd" and are considered part of arc_mru
* that cannot be freed. Generally, they will aquire a DVA
* as they are written and migrate onto the arc_mru list.
*
* The ARC_l2c_only state is for buffers that are in the second
* level ARC but no longer in any of the ARC_m* lists. The second
* level ARC itself may also contain buffers that are in any of
* the ARC_m* states - meaning that a buffer can exist in two
* places. The reason for the ARC_l2c_only state is to keep the
* buffer header in the hash table, so that reads that hit the
* second level ARC benefit from these fast lookups.
*/
typedef struct arc_state {
/*
* list of evictable buffers
*/
multilist_t *arcs_list[ARC_BUFC_NUMTYPES];
/*
* total amount of evictable data in this state
*/
refcount_t arcs_esize[ARC_BUFC_NUMTYPES];
/*
* total amount of data in this state; this includes: evictable,
* non-evictable, ARC_BUFC_DATA, and ARC_BUFC_METADATA.
*/
refcount_t arcs_size;
} arc_state_t;
/* The 6 states: */
static arc_state_t ARC_anon;
static arc_state_t ARC_mru;
static arc_state_t ARC_mru_ghost;
static arc_state_t ARC_mfu;
static arc_state_t ARC_mfu_ghost;
static arc_state_t ARC_l2c_only;
typedef struct arc_stats {
kstat_named_t arcstat_hits;
kstat_named_t arcstat_misses;
kstat_named_t arcstat_demand_data_hits;
kstat_named_t arcstat_demand_data_misses;
kstat_named_t arcstat_demand_metadata_hits;
kstat_named_t arcstat_demand_metadata_misses;
kstat_named_t arcstat_prefetch_data_hits;
kstat_named_t arcstat_prefetch_data_misses;
kstat_named_t arcstat_prefetch_metadata_hits;
kstat_named_t arcstat_prefetch_metadata_misses;
kstat_named_t arcstat_mru_hits;
kstat_named_t arcstat_mru_ghost_hits;
kstat_named_t arcstat_mfu_hits;
kstat_named_t arcstat_mfu_ghost_hits;
kstat_named_t arcstat_allocated;
kstat_named_t arcstat_deleted;
/*
* Number of buffers that could not be evicted because the hash lock
* was held by another thread. The lock may not necessarily be held
* by something using the same buffer, since hash locks are shared
* by multiple buffers.
*/
kstat_named_t arcstat_mutex_miss;
/*
* Number of buffers skipped because they have I/O in progress, are
* indrect prefetch buffers that have not lived long enough, or are
* not from the spa we're trying to evict from.
*/
kstat_named_t arcstat_evict_skip;
/*
* Number of times arc_evict_state() was unable to evict enough
* buffers to reach it's target amount.
*/
kstat_named_t arcstat_evict_not_enough;
kstat_named_t arcstat_evict_l2_cached;
kstat_named_t arcstat_evict_l2_eligible;
kstat_named_t arcstat_evict_l2_ineligible;
kstat_named_t arcstat_evict_l2_skip;
kstat_named_t arcstat_hash_elements;
kstat_named_t arcstat_hash_elements_max;
kstat_named_t arcstat_hash_collisions;
kstat_named_t arcstat_hash_chains;
kstat_named_t arcstat_hash_chain_max;
kstat_named_t arcstat_p;
kstat_named_t arcstat_c;
kstat_named_t arcstat_c_min;
kstat_named_t arcstat_c_max;
kstat_named_t arcstat_size;
/*
* Number of compressed bytes stored in the arc_buf_hdr_t's b_pdata.
* Note that the compressed bytes may match the uncompressed bytes
* if the block is either not compressed or compressed arc is disabled.
*/
kstat_named_t arcstat_compressed_size;
/*
* Uncompressed size of the data stored in b_pdata. If compressed
* arc is disabled then this value will be identical to the stat
* above.
*/
kstat_named_t arcstat_uncompressed_size;
/*
* Number of bytes stored in all the arc_buf_t's. This is classified
* as "overhead" since this data is typically short-lived and will
* be evicted from the arc when it becomes unreferenced unless the
* zfs_keep_uncompressed_metadata or zfs_keep_uncompressed_level
* values have been set (see comment in dbuf.c for more information).
*/
kstat_named_t arcstat_overhead_size;
/*
* Number of bytes consumed by internal ARC structures necessary
* for tracking purposes; these structures are not actually
* backed by ARC buffers. This includes arc_buf_hdr_t structures
* (allocated via arc_buf_hdr_t_full and arc_buf_hdr_t_l2only
* caches), and arc_buf_t structures (allocated via arc_buf_t
* cache).
*/
kstat_named_t arcstat_hdr_size;
/*
* Number of bytes consumed by ARC buffers of type equal to
* ARC_BUFC_DATA. This is generally consumed by buffers backing
* on disk user data (e.g. plain file contents).
*/
kstat_named_t arcstat_data_size;
/*
* Number of bytes consumed by ARC buffers of type equal to
* ARC_BUFC_METADATA. This is generally consumed by buffers
* backing on disk data that is used for internal ZFS
* structures (e.g. ZAP, dnode, indirect blocks, etc).
*/
kstat_named_t arcstat_metadata_size;
/*
* Number of bytes consumed by various buffers and structures
* not actually backed with ARC buffers. This includes bonus
* buffers (allocated directly via zio_buf_* functions),
* dmu_buf_impl_t structures (allocated via dmu_buf_impl_t
* cache), and dnode_t structures (allocated via dnode_t cache).
*/
kstat_named_t arcstat_other_size;
/*
* Total number of bytes consumed by ARC buffers residing in the
* arc_anon state. This includes *all* buffers in the arc_anon
* state; e.g. data, metadata, evictable, and unevictable buffers
* are all included in this value.
*/
kstat_named_t arcstat_anon_size;
/*
* Number of bytes consumed by ARC buffers that meet the
* following criteria: backing buffers of type ARC_BUFC_DATA,
* residing in the arc_anon state, and are eligible for eviction
* (e.g. have no outstanding holds on the buffer).
*/
kstat_named_t arcstat_anon_evictable_data;
/*
* Number of bytes consumed by ARC buffers that meet the
* following criteria: backing buffers of type ARC_BUFC_METADATA,
* residing in the arc_anon state, and are eligible for eviction
* (e.g. have no outstanding holds on the buffer).
*/
kstat_named_t arcstat_anon_evictable_metadata;
/*
* Total number of bytes consumed by ARC buffers residing in the
* arc_mru state. This includes *all* buffers in the arc_mru
* state; e.g. data, metadata, evictable, and unevictable buffers
* are all included in this value.
*/
kstat_named_t arcstat_mru_size;
/*
* Number of bytes consumed by ARC buffers that meet the
* following criteria: backing buffers of type ARC_BUFC_DATA,
* residing in the arc_mru state, and are eligible for eviction
* (e.g. have no outstanding holds on the buffer).
*/
kstat_named_t arcstat_mru_evictable_data;
/*
* Number of bytes consumed by ARC buffers that meet the
* following criteria: backing buffers of type ARC_BUFC_METADATA,
* residing in the arc_mru state, and are eligible for eviction
* (e.g. have no outstanding holds on the buffer).
*/
kstat_named_t arcstat_mru_evictable_metadata;
/*
* Total number of bytes that *would have been* consumed by ARC
* buffers in the arc_mru_ghost state. The key thing to note
* here, is the fact that this size doesn't actually indicate
* RAM consumption. The ghost lists only consist of headers and
* don't actually have ARC buffers linked off of these headers.
* Thus, *if* the headers had associated ARC buffers, these
* buffers *would have* consumed this number of bytes.
*/
kstat_named_t arcstat_mru_ghost_size;
/*
* Number of bytes that *would have been* consumed by ARC
* buffers that are eligible for eviction, of type
* ARC_BUFC_DATA, and linked off the arc_mru_ghost state.
*/
kstat_named_t arcstat_mru_ghost_evictable_data;
/*
* Number of bytes that *would have been* consumed by ARC
* buffers that are eligible for eviction, of type
* ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
*/
kstat_named_t arcstat_mru_ghost_evictable_metadata;
/*
* Total number of bytes consumed by ARC buffers residing in the
* arc_mfu state. This includes *all* buffers in the arc_mfu
* state; e.g. data, metadata, evictable, and unevictable buffers
* are all included in this value.
*/
kstat_named_t arcstat_mfu_size;
/*
* Number of bytes consumed by ARC buffers that are eligible for
* eviction, of type ARC_BUFC_DATA, and reside in the arc_mfu
* state.
*/
kstat_named_t arcstat_mfu_evictable_data;
/*
* Number of bytes consumed by ARC buffers that are eligible for
* eviction, of type ARC_BUFC_METADATA, and reside in the
* arc_mfu state.
*/
kstat_named_t arcstat_mfu_evictable_metadata;
/*
* Total number of bytes that *would have been* consumed by ARC
* buffers in the arc_mfu_ghost state. See the comment above
* arcstat_mru_ghost_size for more details.
*/
kstat_named_t arcstat_mfu_ghost_size;
/*
* Number of bytes that *would have been* consumed by ARC
* buffers that are eligible for eviction, of type
* ARC_BUFC_DATA, and linked off the arc_mfu_ghost state.
*/
kstat_named_t arcstat_mfu_ghost_evictable_data;
/*
* Number of bytes that *would have been* consumed by ARC
* buffers that are eligible for eviction, of type
* ARC_BUFC_METADATA, and linked off the arc_mru_ghost state.
*/
kstat_named_t arcstat_mfu_ghost_evictable_metadata;
kstat_named_t arcstat_l2_hits;
kstat_named_t arcstat_l2_misses;
kstat_named_t arcstat_l2_feeds;
kstat_named_t arcstat_l2_rw_clash;
kstat_named_t arcstat_l2_read_bytes;
kstat_named_t arcstat_l2_write_bytes;
kstat_named_t arcstat_l2_writes_sent;
kstat_named_t arcstat_l2_writes_done;
kstat_named_t arcstat_l2_writes_error;
kstat_named_t arcstat_l2_writes_lock_retry;
kstat_named_t arcstat_l2_evict_lock_retry;
kstat_named_t arcstat_l2_evict_reading;
kstat_named_t arcstat_l2_evict_l1cached;
kstat_named_t arcstat_l2_free_on_write;
kstat_named_t arcstat_l2_abort_lowmem;
kstat_named_t arcstat_l2_cksum_bad;
kstat_named_t arcstat_l2_io_error;
kstat_named_t arcstat_l2_size;
kstat_named_t arcstat_l2_asize;
kstat_named_t arcstat_l2_hdr_size;
kstat_named_t arcstat_l2_write_trylock_fail;
kstat_named_t arcstat_l2_write_passed_headroom;
kstat_named_t arcstat_l2_write_spa_mismatch;
kstat_named_t arcstat_l2_write_in_l2;
kstat_named_t arcstat_l2_write_hdr_io_in_progress;
kstat_named_t arcstat_l2_write_not_cacheable;
kstat_named_t arcstat_l2_write_full;
kstat_named_t arcstat_l2_write_buffer_iter;
kstat_named_t arcstat_l2_write_pios;
kstat_named_t arcstat_l2_write_buffer_bytes_scanned;
kstat_named_t arcstat_l2_write_buffer_list_iter;
kstat_named_t arcstat_l2_write_buffer_list_null_iter;
kstat_named_t arcstat_memory_throttle_count;
kstat_named_t arcstat_meta_used;
kstat_named_t arcstat_meta_limit;
kstat_named_t arcstat_meta_max;
kstat_named_t arcstat_meta_min;
kstat_named_t arcstat_sync_wait_for_async;
kstat_named_t arcstat_demand_hit_predictive_prefetch;
} arc_stats_t;
static arc_stats_t arc_stats = {
{ "hits", KSTAT_DATA_UINT64 },
{ "misses", KSTAT_DATA_UINT64 },
{ "demand_data_hits", KSTAT_DATA_UINT64 },
{ "demand_data_misses", KSTAT_DATA_UINT64 },
{ "demand_metadata_hits", KSTAT_DATA_UINT64 },
{ "demand_metadata_misses", KSTAT_DATA_UINT64 },
{ "prefetch_data_hits", KSTAT_DATA_UINT64 },
{ "prefetch_data_misses", KSTAT_DATA_UINT64 },
{ "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
{ "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
{ "mru_hits", KSTAT_DATA_UINT64 },
{ "mru_ghost_hits", KSTAT_DATA_UINT64 },
{ "mfu_hits", KSTAT_DATA_UINT64 },
{ "mfu_ghost_hits", KSTAT_DATA_UINT64 },
{ "allocated", KSTAT_DATA_UINT64 },
{ "deleted", KSTAT_DATA_UINT64 },
{ "mutex_miss", KSTAT_DATA_UINT64 },
{ "evict_skip", KSTAT_DATA_UINT64 },
{ "evict_not_enough", KSTAT_DATA_UINT64 },
{ "evict_l2_cached", KSTAT_DATA_UINT64 },
{ "evict_l2_eligible", KSTAT_DATA_UINT64 },
{ "evict_l2_ineligible", KSTAT_DATA_UINT64 },
{ "evict_l2_skip", KSTAT_DATA_UINT64 },
{ "hash_elements", KSTAT_DATA_UINT64 },
{ "hash_elements_max", KSTAT_DATA_UINT64 },
{ "hash_collisions", KSTAT_DATA_UINT64 },
{ "hash_chains", KSTAT_DATA_UINT64 },
{ "hash_chain_max", KSTAT_DATA_UINT64 },
{ "p", KSTAT_DATA_UINT64 },
{ "c", KSTAT_DATA_UINT64 },
{ "c_min", KSTAT_DATA_UINT64 },
{ "c_max", KSTAT_DATA_UINT64 },
{ "size", KSTAT_DATA_UINT64 },
{ "compressed_size", KSTAT_DATA_UINT64 },
{ "uncompressed_size", KSTAT_DATA_UINT64 },
{ "overhead_size", KSTAT_DATA_UINT64 },
{ "hdr_size", KSTAT_DATA_UINT64 },
{ "data_size", KSTAT_DATA_UINT64 },
{ "metadata_size", KSTAT_DATA_UINT64 },
{ "other_size", KSTAT_DATA_UINT64 },
{ "anon_size", KSTAT_DATA_UINT64 },
{ "anon_evictable_data", KSTAT_DATA_UINT64 },
{ "anon_evictable_metadata", KSTAT_DATA_UINT64 },
{ "mru_size", KSTAT_DATA_UINT64 },
{ "mru_evictable_data", KSTAT_DATA_UINT64 },
{ "mru_evictable_metadata", KSTAT_DATA_UINT64 },
{ "mru_ghost_size", KSTAT_DATA_UINT64 },
{ "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
{ "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
{ "mfu_size", KSTAT_DATA_UINT64 },
{ "mfu_evictable_data", KSTAT_DATA_UINT64 },
{ "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
{ "mfu_ghost_size", KSTAT_DATA_UINT64 },
{ "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
{ "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
{ "l2_hits", KSTAT_DATA_UINT64 },
{ "l2_misses", KSTAT_DATA_UINT64 },
{ "l2_feeds", KSTAT_DATA_UINT64 },
{ "l2_rw_clash", KSTAT_DATA_UINT64 },
{ "l2_read_bytes", KSTAT_DATA_UINT64 },
{ "l2_write_bytes", KSTAT_DATA_UINT64 },
{ "l2_writes_sent", KSTAT_DATA_UINT64 },
{ "l2_writes_done", KSTAT_DATA_UINT64 },
{ "l2_writes_error", KSTAT_DATA_UINT64 },
{ "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
{ "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
{ "l2_evict_reading", KSTAT_DATA_UINT64 },
{ "l2_evict_l1cached", KSTAT_DATA_UINT64 },
{ "l2_free_on_write", KSTAT_DATA_UINT64 },
{ "l2_abort_lowmem", KSTAT_DATA_UINT64 },
{ "l2_cksum_bad", KSTAT_DATA_UINT64 },
{ "l2_io_error", KSTAT_DATA_UINT64 },
{ "l2_size", KSTAT_DATA_UINT64 },
{ "l2_asize", KSTAT_DATA_UINT64 },
{ "l2_hdr_size", KSTAT_DATA_UINT64 },
{ "l2_write_trylock_fail", KSTAT_DATA_UINT64 },
{ "l2_write_passed_headroom", KSTAT_DATA_UINT64 },
{ "l2_write_spa_mismatch", KSTAT_DATA_UINT64 },
{ "l2_write_in_l2", KSTAT_DATA_UINT64 },
{ "l2_write_io_in_progress", KSTAT_DATA_UINT64 },
{ "l2_write_not_cacheable", KSTAT_DATA_UINT64 },
{ "l2_write_full", KSTAT_DATA_UINT64 },
{ "l2_write_buffer_iter", KSTAT_DATA_UINT64 },
{ "l2_write_pios", KSTAT_DATA_UINT64 },
{ "l2_write_buffer_bytes_scanned", KSTAT_DATA_UINT64 },
{ "l2_write_buffer_list_iter", KSTAT_DATA_UINT64 },
{ "l2_write_buffer_list_null_iter", KSTAT_DATA_UINT64 },
{ "memory_throttle_count", KSTAT_DATA_UINT64 },
{ "arc_meta_used", KSTAT_DATA_UINT64 },
{ "arc_meta_limit", KSTAT_DATA_UINT64 },
{ "arc_meta_max", KSTAT_DATA_UINT64 },
{ "arc_meta_min", KSTAT_DATA_UINT64 },
{ "sync_wait_for_async", KSTAT_DATA_UINT64 },
{ "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 },
};
#define ARCSTAT(stat) (arc_stats.stat.value.ui64)
#define ARCSTAT_INCR(stat, val) \
atomic_add_64(&arc_stats.stat.value.ui64, (val))
#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
#define ARCSTAT_MAX(stat, val) { \
uint64_t m; \
while ((val) > (m = arc_stats.stat.value.ui64) && \
(m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
continue; \
}
#define ARCSTAT_MAXSTAT(stat) \
ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
/*
* We define a macro to allow ARC hits/misses to be easily broken down by
* two separate conditions, giving a total of four different subtypes for
* each of hits and misses (so eight statistics total).
*/
#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
if (cond1) { \
if (cond2) { \
ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
} else { \
ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
} \
} else { \
if (cond2) { \
ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
} else { \
ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
} \
}
kstat_t *arc_ksp;
static arc_state_t *arc_anon;
static arc_state_t *arc_mru;
static arc_state_t *arc_mru_ghost;
static arc_state_t *arc_mfu;
static arc_state_t *arc_mfu_ghost;
static arc_state_t *arc_l2c_only;
/*
* There are several ARC variables that are critical to export as kstats --
* but we don't want to have to grovel around in the kstat whenever we wish to
* manipulate them. For these variables, we therefore define them to be in
* terms of the statistic variable. This assures that we are not introducing
* the possibility of inconsistency by having shadow copies of the variables,
* while still allowing the code to be readable.
*/
#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
#define arc_c ARCSTAT(arcstat_c) /* target size of cache */
#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
#define arc_meta_min ARCSTAT(arcstat_meta_min) /* min size for metadata */
#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
/* compressed size of entire arc */
#define arc_compressed_size ARCSTAT(arcstat_compressed_size)
/* uncompressed size of entire arc */
#define arc_uncompressed_size ARCSTAT(arcstat_uncompressed_size)
/* number of bytes in the arc from arc_buf_t's */
#define arc_overhead_size ARCSTAT(arcstat_overhead_size)
static int arc_no_grow; /* Don't try to grow cache size */
static uint64_t arc_tempreserve;
static uint64_t arc_loaned_bytes;
typedef struct arc_callback arc_callback_t;
struct arc_callback {
void *acb_private;
arc_done_func_t *acb_done;
arc_buf_t *acb_buf;
boolean_t acb_compressed;
zio_t *acb_zio_dummy;
arc_callback_t *acb_next;
};
typedef struct arc_write_callback arc_write_callback_t;
struct arc_write_callback {
void *awcb_private;
arc_done_func_t *awcb_ready;
arc_done_func_t *awcb_children_ready;
arc_done_func_t *awcb_physdone;
arc_done_func_t *awcb_done;
arc_buf_t *awcb_buf;
};
/*
* ARC buffers are separated into multiple structs as a memory saving measure:
* - Common fields struct, always defined, and embedded within it:
* - L2-only fields, always allocated but undefined when not in L2ARC
* - L1-only fields, only allocated when in L1ARC
*
* Buffer in L1 Buffer only in L2
* +------------------------+ +------------------------+
* | arc_buf_hdr_t | | arc_buf_hdr_t |
* | | | |
* | | | |
* | | | |
* +------------------------+ +------------------------+
* | l2arc_buf_hdr_t | | l2arc_buf_hdr_t |
* | (undefined if L1-only) | | |
* +------------------------+ +------------------------+
* | l1arc_buf_hdr_t |
* | |
* | |
* | |
* | |
* +------------------------+
*
* Because it's possible for the L2ARC to become extremely large, we can wind
* up eating a lot of memory in L2ARC buffer headers, so the size of a header
* is minimized by only allocating the fields necessary for an L1-cached buffer
* when a header is actually in the L1 cache. The sub-headers (l1arc_buf_hdr and
* l2arc_buf_hdr) are embedded rather than allocated separately to save a couple
* words in pointers. arc_hdr_realloc() is used to switch a header between
* these two allocation states.
*/
typedef struct l1arc_buf_hdr {
kmutex_t b_freeze_lock;
zio_cksum_t *b_freeze_cksum;
#ifdef ZFS_DEBUG
/*
* Used for debugging with kmem_flags - by allocating and freeing
* b_thawed when the buffer is thawed, we get a record of the stack
* trace that thawed it.
*/
void *b_thawed;
#endif
arc_buf_t *b_buf;
uint32_t b_bufcnt;
/* for waiting on writes to complete */
kcondvar_t b_cv;
uint8_t b_byteswap;
/* protected by arc state mutex */
arc_state_t *b_state;
multilist_node_t b_arc_node;
/* updated atomically */
clock_t b_arc_access;
/* self protecting */
refcount_t b_refcnt;
arc_callback_t *b_acb;
void *b_pdata;
} l1arc_buf_hdr_t;
typedef struct l2arc_dev l2arc_dev_t;
typedef struct l2arc_buf_hdr {
/* protected by arc_buf_hdr mutex */
l2arc_dev_t *b_dev; /* L2ARC device */
uint64_t b_daddr; /* disk address, offset byte */
list_node_t b_l2node;
} l2arc_buf_hdr_t;
struct arc_buf_hdr {
/* protected by hash lock */
dva_t b_dva;
uint64_t b_birth;
arc_buf_contents_t b_type;
arc_buf_hdr_t *b_hash_next;
arc_flags_t b_flags;
/*
* This field stores the size of the data buffer after
* compression, and is set in the arc's zio completion handlers.
* It is in units of SPA_MINBLOCKSIZE (e.g. 1 == 512 bytes).
*
* While the block pointers can store up to 32MB in their psize
* field, we can only store up to 32MB minus 512B. This is due
* to the bp using a bias of 1, whereas we use a bias of 0 (i.e.
* a field of zeros represents 512B in the bp). We can't use a
* bias of 1 since we need to reserve a psize of zero, here, to
* represent holes and embedded blocks.
*
* This isn't a problem in practice, since the maximum size of a
* buffer is limited to 16MB, so we never need to store 32MB in
* this field. Even in the upstream illumos code base, the
* maximum size of a buffer is limited to 16MB.
*/
uint16_t b_psize;
/*
* This field stores the size of the data buffer before
* compression, and cannot change once set. It is in units
* of SPA_MINBLOCKSIZE (e.g. 2 == 1024 bytes)
*/
uint16_t b_lsize; /* immutable */
uint64_t b_spa; /* immutable */
/* L2ARC fields. Undefined when not in L2ARC. */
l2arc_buf_hdr_t b_l2hdr;
/* L1ARC fields. Undefined when in l2arc_only state */
l1arc_buf_hdr_t b_l1hdr;
};
#if defined(__FreeBSD__) && defined(_KERNEL)
static int
sysctl_vfs_zfs_arc_meta_limit(SYSCTL_HANDLER_ARGS)
{
uint64_t val;
int err;
val = arc_meta_limit;
err = sysctl_handle_64(oidp, &val, 0, req);
if (err != 0 || req->newptr == NULL)
return (err);
if (val <= 0 || val > arc_c_max)
return (EINVAL);
arc_meta_limit = val;
return (0);
}
static int
sysctl_vfs_zfs_arc_max(SYSCTL_HANDLER_ARGS)
{
uint64_t val;
int err;
val = zfs_arc_max;
err = sysctl_handle_64(oidp, &val, 0, req);
if (err != 0 || req->newptr == NULL)
return (err);
if (zfs_arc_max == 0) {
/* Loader tunable so blindly set */
zfs_arc_max = val;
return (0);
}
if (val < arc_abs_min || val > kmem_size())
return (EINVAL);
if (val < arc_c_min)
return (EINVAL);
if (zfs_arc_meta_limit > 0 && val < zfs_arc_meta_limit)
return (EINVAL);
arc_c_max = val;
arc_c = arc_c_max;
arc_p = (arc_c >> 1);
if (zfs_arc_meta_limit == 0) {
/* limit meta-data to 1/4 of the arc capacity */
arc_meta_limit = arc_c_max / 4;
}
/* if kmem_flags are set, lets try to use less memory */
if (kmem_debugging())
arc_c = arc_c / 2;
zfs_arc_max = arc_c;
return (0);
}
static int
sysctl_vfs_zfs_arc_min(SYSCTL_HANDLER_ARGS)
{
uint64_t val;
int err;
val = zfs_arc_min;
err = sysctl_handle_64(oidp, &val, 0, req);
if (err != 0 || req->newptr == NULL)
return (err);
if (zfs_arc_min == 0) {
/* Loader tunable so blindly set */
zfs_arc_min = val;
return (0);
}
if (val < arc_abs_min || val > arc_c_max)
return (EINVAL);
arc_c_min = val;
if (zfs_arc_meta_min == 0)
arc_meta_min = arc_c_min / 2;
if (arc_c < arc_c_min)
arc_c = arc_c_min;
zfs_arc_min = arc_c_min;
return (0);
}
#endif
#define GHOST_STATE(state) \
((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
(state) == arc_l2c_only)
#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
#define HDR_COMPRESSION_ENABLED(hdr) \
((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC)
#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
#define HDR_L2_READING(hdr) \
(((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
#define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA)
#define HDR_ISTYPE_METADATA(hdr) \
((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
#define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
#define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
#define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
/* For storing compression mode in b_flags */
#define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1)
#define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \
HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS))
#define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \
HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp));
#define ARC_BUF_LAST(buf) ((buf)->b_next == NULL)
#define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED)
#define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED)
/*
* Other sizes
*/
#define HDR_FULL_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
#define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
/*
* Hash table routines
*/
#define HT_LOCK_PAD CACHE_LINE_SIZE
struct ht_lock {
kmutex_t ht_lock;
#ifdef _KERNEL
unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
#endif
};
#define BUF_LOCKS 256
typedef struct buf_hash_table {
uint64_t ht_mask;
arc_buf_hdr_t **ht_table;
struct ht_lock ht_locks[BUF_LOCKS] __aligned(CACHE_LINE_SIZE);
} buf_hash_table_t;
static buf_hash_table_t buf_hash_table;
#define BUF_HASH_INDEX(spa, dva, birth) \
(buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
#define HDR_LOCK(hdr) \
(BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
uint64_t zfs_crc64_table[256];
/*
* Level 2 ARC
*/
#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
#define L2ARC_HEADROOM 2 /* num of writes */
/*
* If we discover during ARC scan any buffers to be compressed, we boost
* our headroom for the next scanning cycle by this percentage multiple.
*/
#define L2ARC_HEADROOM_BOOST 200
#define L2ARC_FEED_SECS 1 /* caching interval secs */
#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
/* L2ARC Performance Tunables */
uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_max, CTLFLAG_RW,
&l2arc_write_max, 0, "max write size");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_write_boost, CTLFLAG_RW,
&l2arc_write_boost, 0, "extra write during warmup");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_headroom, CTLFLAG_RW,
&l2arc_headroom, 0, "number of dev writes");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_secs, CTLFLAG_RW,
&l2arc_feed_secs, 0, "interval seconds");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2arc_feed_min_ms, CTLFLAG_RW,
&l2arc_feed_min_ms, 0, "min interval milliseconds");
SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_noprefetch, CTLFLAG_RW,
&l2arc_noprefetch, 0, "don't cache prefetch bufs");
SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_feed_again, CTLFLAG_RW,
&l2arc_feed_again, 0, "turbo warmup");
SYSCTL_INT(_vfs_zfs, OID_AUTO, l2arc_norw, CTLFLAG_RW,
&l2arc_norw, 0, "no reads during writes");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_size, CTLFLAG_RD,
&ARC_anon.arcs_size.rc_count, 0, "size of anonymous state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_metadata_esize, CTLFLAG_RD,
&ARC_anon.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
"size of anonymous state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, anon_data_esize, CTLFLAG_RD,
&ARC_anon.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
"size of anonymous state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_size, CTLFLAG_RD,
&ARC_mru.arcs_size.rc_count, 0, "size of mru state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_metadata_esize, CTLFLAG_RD,
&ARC_mru.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
"size of metadata in mru state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_data_esize, CTLFLAG_RD,
&ARC_mru.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
"size of data in mru state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_size, CTLFLAG_RD,
&ARC_mru_ghost.arcs_size.rc_count, 0, "size of mru ghost state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_metadata_esize, CTLFLAG_RD,
&ARC_mru_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
"size of metadata in mru ghost state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mru_ghost_data_esize, CTLFLAG_RD,
&ARC_mru_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
"size of data in mru ghost state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_size, CTLFLAG_RD,
&ARC_mfu.arcs_size.rc_count, 0, "size of mfu state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_metadata_esize, CTLFLAG_RD,
&ARC_mfu.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
"size of metadata in mfu state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_data_esize, CTLFLAG_RD,
&ARC_mfu.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
"size of data in mfu state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_size, CTLFLAG_RD,
&ARC_mfu_ghost.arcs_size.rc_count, 0, "size of mfu ghost state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_metadata_esize, CTLFLAG_RD,
&ARC_mfu_ghost.arcs_esize[ARC_BUFC_METADATA].rc_count, 0,
"size of metadata in mfu ghost state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, mfu_ghost_data_esize, CTLFLAG_RD,
&ARC_mfu_ghost.arcs_esize[ARC_BUFC_DATA].rc_count, 0,
"size of data in mfu ghost state");
SYSCTL_UQUAD(_vfs_zfs, OID_AUTO, l2c_only_size, CTLFLAG_RD,
&ARC_l2c_only.arcs_size.rc_count, 0, "size of mru state");
/*
* L2ARC Internals
*/
struct l2arc_dev {
vdev_t *l2ad_vdev; /* vdev */
spa_t *l2ad_spa; /* spa */
uint64_t l2ad_hand; /* next write location */
uint64_t l2ad_start; /* first addr on device */
uint64_t l2ad_end; /* last addr on device */
boolean_t l2ad_first; /* first sweep through */
boolean_t l2ad_writing; /* currently writing */
kmutex_t l2ad_mtx; /* lock for buffer list */
list_t l2ad_buflist; /* buffer list */
list_node_t l2ad_node; /* device list node */
refcount_t l2ad_alloc; /* allocated bytes */
};
static list_t L2ARC_dev_list; /* device list */
static list_t *l2arc_dev_list; /* device list pointer */
static kmutex_t l2arc_dev_mtx; /* device list mutex */
static l2arc_dev_t *l2arc_dev_last; /* last device used */
static list_t L2ARC_free_on_write; /* free after write buf list */
static list_t *l2arc_free_on_write; /* free after write list ptr */
static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
static uint64_t l2arc_ndev; /* number of devices */
typedef struct l2arc_read_callback {
arc_buf_hdr_t *l2rcb_hdr; /* read header */
blkptr_t l2rcb_bp; /* original blkptr */
zbookmark_phys_t l2rcb_zb; /* original bookmark */
int l2rcb_flags; /* original flags */
void *l2rcb_data; /* temporary buffer */
} l2arc_read_callback_t;
typedef struct l2arc_write_callback {
l2arc_dev_t *l2wcb_dev; /* device info */
arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
} l2arc_write_callback_t;
typedef struct l2arc_data_free {
/* protected by l2arc_free_on_write_mtx */
void *l2df_data;
size_t l2df_size;
arc_buf_contents_t l2df_type;
list_node_t l2df_list_node;
} l2arc_data_free_t;
static kmutex_t l2arc_feed_thr_lock;
static kcondvar_t l2arc_feed_thr_cv;
static uint8_t l2arc_thread_exit;
static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *);
static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *);
static void arc_hdr_free_pdata(arc_buf_hdr_t *hdr);
static void arc_hdr_alloc_pdata(arc_buf_hdr_t *);
static void arc_access(arc_buf_hdr_t *, kmutex_t *);
static boolean_t arc_is_overflowing();
static void arc_buf_watch(arc_buf_t *);
static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
static void l2arc_read_done(zio_t *);
static void
l2arc_trim(const arc_buf_hdr_t *hdr)
{
l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
ASSERT(HDR_HAS_L2HDR(hdr));
ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
if (HDR_GET_PSIZE(hdr) != 0) {
trim_map_free(dev->l2ad_vdev, hdr->b_l2hdr.b_daddr,
HDR_GET_PSIZE(hdr), 0);
}
}
static uint64_t
buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
{
uint8_t *vdva = (uint8_t *)dva;
uint64_t crc = -1ULL;
int i;
ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
for (i = 0; i < sizeof (dva_t); i++)
crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
crc ^= (spa>>8) ^ birth;
return (crc);
}
#define HDR_EMPTY(hdr) \
((hdr)->b_dva.dva_word[0] == 0 && \
(hdr)->b_dva.dva_word[1] == 0)
#define HDR_EQUAL(spa, dva, birth, hdr) \
((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
((hdr)->b_birth == birth) && ((hdr)->b_spa == spa)
static void
buf_discard_identity(arc_buf_hdr_t *hdr)
{
hdr->b_dva.dva_word[0] = 0;
hdr->b_dva.dva_word[1] = 0;
hdr->b_birth = 0;
}
static arc_buf_hdr_t *
buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
{
const dva_t *dva = BP_IDENTITY(bp);
uint64_t birth = BP_PHYSICAL_BIRTH(bp);
uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
arc_buf_hdr_t *hdr;
mutex_enter(hash_lock);
for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
hdr = hdr->b_hash_next) {
if (HDR_EQUAL(spa, dva, birth, hdr)) {
*lockp = hash_lock;
return (hdr);
}
}
mutex_exit(hash_lock);
*lockp = NULL;
return (NULL);
}
/*
* Insert an entry into the hash table. If there is already an element
* equal to elem in the hash table, then the already existing element
* will be returned and the new element will not be inserted.
* Otherwise returns NULL.
* If lockp == NULL, the caller is assumed to already hold the hash lock.
*/
static arc_buf_hdr_t *
buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
{
uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
arc_buf_hdr_t *fhdr;
uint32_t i;
ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
ASSERT(hdr->b_birth != 0);
ASSERT(!HDR_IN_HASH_TABLE(hdr));
if (lockp != NULL) {
*lockp = hash_lock;
mutex_enter(hash_lock);
} else {
ASSERT(MUTEX_HELD(hash_lock));
}
for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
fhdr = fhdr->b_hash_next, i++) {
if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
return (fhdr);
}
hdr->b_hash_next = buf_hash_table.ht_table[idx];
buf_hash_table.ht_table[idx] = hdr;
arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
/* collect some hash table performance data */
if (i > 0) {
ARCSTAT_BUMP(arcstat_hash_collisions);
if (i == 1)
ARCSTAT_BUMP(arcstat_hash_chains);
ARCSTAT_MAX(arcstat_hash_chain_max, i);
}
ARCSTAT_BUMP(arcstat_hash_elements);
ARCSTAT_MAXSTAT(arcstat_hash_elements);
return (NULL);
}
static void
buf_hash_remove(arc_buf_hdr_t *hdr)
{
arc_buf_hdr_t *fhdr, **hdrp;
uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
ASSERT(HDR_IN_HASH_TABLE(hdr));
hdrp = &buf_hash_table.ht_table[idx];
while ((fhdr = *hdrp) != hdr) {
ASSERT3P(fhdr, !=, NULL);
hdrp = &fhdr->b_hash_next;
}
*hdrp = hdr->b_hash_next;
hdr->b_hash_next = NULL;
arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
/* collect some hash table performance data */
ARCSTAT_BUMPDOWN(arcstat_hash_elements);
if (buf_hash_table.ht_table[idx] &&
buf_hash_table.ht_table[idx]->b_hash_next == NULL)
ARCSTAT_BUMPDOWN(arcstat_hash_chains);
}
/*
* Global data structures and functions for the buf kmem cache.
*/
static kmem_cache_t *hdr_full_cache;
static kmem_cache_t *hdr_l2only_cache;
static kmem_cache_t *buf_cache;
static void
buf_fini(void)
{
int i;
kmem_free(buf_hash_table.ht_table,
(buf_hash_table.ht_mask + 1) * sizeof (void *));
for (i = 0; i < BUF_LOCKS; i++)
mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
kmem_cache_destroy(hdr_full_cache);
kmem_cache_destroy(hdr_l2only_cache);
kmem_cache_destroy(buf_cache);
}
/*
* Constructor callback - called when the cache is empty
* and a new buf is requested.
*/
/* ARGSUSED */
static int
hdr_full_cons(void *vbuf, void *unused, int kmflag)
{
arc_buf_hdr_t *hdr = vbuf;
bzero(hdr, HDR_FULL_SIZE);
cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
refcount_create(&hdr->b_l1hdr.b_refcnt);
mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
multilist_link_init(&hdr->b_l1hdr.b_arc_node);
arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
return (0);
}
/* ARGSUSED */
static int
hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
{
arc_buf_hdr_t *hdr = vbuf;
bzero(hdr, HDR_L2ONLY_SIZE);
arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
return (0);
}
/* ARGSUSED */
static int
buf_cons(void *vbuf, void *unused, int kmflag)
{
arc_buf_t *buf = vbuf;
bzero(buf, sizeof (arc_buf_t));
mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
return (0);
}
/*
* Destructor callback - called when a cached buf is
* no longer required.
*/
/* ARGSUSED */
static void
hdr_full_dest(void *vbuf, void *unused)
{
arc_buf_hdr_t *hdr = vbuf;
ASSERT(HDR_EMPTY(hdr));
cv_destroy(&hdr->b_l1hdr.b_cv);
refcount_destroy(&hdr->b_l1hdr.b_refcnt);
mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
}
/* ARGSUSED */
static void
hdr_l2only_dest(void *vbuf, void *unused)
{
arc_buf_hdr_t *hdr = vbuf;
ASSERT(HDR_EMPTY(hdr));
arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
}
/* ARGSUSED */
static void
buf_dest(void *vbuf, void *unused)
{
arc_buf_t *buf = vbuf;
mutex_destroy(&buf->b_evict_lock);
arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
}
/*
* Reclaim callback -- invoked when memory is low.
*/
/* ARGSUSED */
static void
hdr_recl(void *unused)
{
dprintf("hdr_recl called\n");
/*
* umem calls the reclaim func when we destroy the buf cache,
* which is after we do arc_fini().
*/
if (!arc_dead)
cv_signal(&arc_reclaim_thread_cv);
}
static void
buf_init(void)
{
uint64_t *ct;
uint64_t hsize = 1ULL << 12;
int i, j;
/*
* The hash table is big enough to fill all of physical memory
* with an average block size of zfs_arc_average_blocksize (default 8K).
* By default, the table will take up
* totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
*/
while (hsize * zfs_arc_average_blocksize < (uint64_t)physmem * PAGESIZE)
hsize <<= 1;
retry:
buf_hash_table.ht_mask = hsize - 1;
buf_hash_table.ht_table =
kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
if (buf_hash_table.ht_table == NULL) {
ASSERT(hsize > (1ULL << 8));
hsize >>= 1;
goto retry;
}
hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
NULL, NULL, 0);
buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
for (i = 0; i < 256; i++)
for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
*ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
for (i = 0; i < BUF_LOCKS; i++) {
mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
NULL, MUTEX_DEFAULT, NULL);
}
}
/*
* This is the size that the buf occupies in memory. If the buf is compressed,
* it will correspond to the compressed size. You should use this method of
* getting the buf size unless you explicitly need the logical size.
*/
int32_t
arc_buf_size(arc_buf_t *buf)
{
return (ARC_BUF_COMPRESSED(buf) ?
HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr));
}
int32_t
arc_buf_lsize(arc_buf_t *buf)
{
return (HDR_GET_LSIZE(buf->b_hdr));
}
enum zio_compress
arc_get_compression(arc_buf_t *buf)
{
return (ARC_BUF_COMPRESSED(buf) ?
HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF);
}
#define ARC_MINTIME (hz>>4) /* 62 ms */
static inline boolean_t
arc_buf_is_shared(arc_buf_t *buf)
{
boolean_t shared = (buf->b_data != NULL &&
buf->b_data == buf->b_hdr->b_l1hdr.b_pdata);
IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr));
IMPLY(shared, ARC_BUF_SHARED(buf));
IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf));
/*
* It would be nice to assert arc_can_share() too, but the "hdr isn't
* already being shared" requirement prevents us from doing that.
*/
return (shared);
}
/*
* Free the checksum associated with this header. If there is no checksum, this
* is a no-op.
*/
static inline void
arc_cksum_free(arc_buf_hdr_t *hdr)
{
ASSERT(HDR_HAS_L1HDR(hdr));
mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t));
hdr->b_l1hdr.b_freeze_cksum = NULL;
}
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
}
/*
* Return true iff at least one of the bufs on hdr is not compressed.
*/
static boolean_t
arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr)
{
for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) {
if (!ARC_BUF_COMPRESSED(b)) {
return (B_TRUE);
}
}
return (B_FALSE);
}
/*
* If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data
* matches the checksum that is stored in the hdr. If there is no checksum,
* or if the buf is compressed, this is a no-op.
*/
static void
arc_cksum_verify(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
zio_cksum_t zc;
if (!(zfs_flags & ZFS_DEBUG_MODIFY))
return;
if (ARC_BUF_COMPRESSED(buf)) {
ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
arc_hdr_has_uncompressed_buf(hdr));
return;
}
ASSERT(HDR_HAS_L1HDR(hdr));
mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) {
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
return;
}
fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc);
if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc))
panic("buffer modified while frozen!");
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
}
static boolean_t
arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio)
{
enum zio_compress compress = BP_GET_COMPRESS(zio->io_bp);
boolean_t valid_cksum;
ASSERT(!BP_IS_EMBEDDED(zio->io_bp));
VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr));
/*
* We rely on the blkptr's checksum to determine if the block
* is valid or not. When compressed arc is enabled, the l2arc
* writes the block to the l2arc just as it appears in the pool.
* This allows us to use the blkptr's checksum to validate the
* data that we just read off of the l2arc without having to store
* a separate checksum in the arc_buf_hdr_t. However, if compressed
* arc is disabled, then the data written to the l2arc is always
* uncompressed and won't match the block as it exists in the main
* pool. When this is the case, we must first compress it if it is
* compressed on the main pool before we can validate the checksum.
*/
if (!HDR_COMPRESSION_ENABLED(hdr) && compress != ZIO_COMPRESS_OFF) {
ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
uint64_t lsize = HDR_GET_LSIZE(hdr);
uint64_t csize;
void *cbuf = zio_buf_alloc(HDR_GET_PSIZE(hdr));
csize = zio_compress_data(compress, zio->io_data, cbuf, lsize);
ASSERT3U(csize, <=, HDR_GET_PSIZE(hdr));
if (csize < HDR_GET_PSIZE(hdr)) {
/*
* Compressed blocks are always a multiple of the
* smallest ashift in the pool. Ideally, we would
* like to round up the csize to the next
* spa_min_ashift but that value may have changed
* since the block was last written. Instead,
* we rely on the fact that the hdr's psize
* was set to the psize of the block when it was
* last written. We set the csize to that value
* and zero out any part that should not contain
* data.
*/
bzero((char *)cbuf + csize, HDR_GET_PSIZE(hdr) - csize);
csize = HDR_GET_PSIZE(hdr);
}
zio_push_transform(zio, cbuf, csize, HDR_GET_PSIZE(hdr), NULL);
}
/*
* Block pointers always store the checksum for the logical data.
* If the block pointer has the gang bit set, then the checksum
* it represents is for the reconstituted data and not for an
* individual gang member. The zio pipeline, however, must be able to
* determine the checksum of each of the gang constituents so it
* treats the checksum comparison differently than what we need
* for l2arc blocks. This prevents us from using the
* zio_checksum_error() interface directly. Instead we must call the
* zio_checksum_error_impl() so that we can ensure the checksum is
* generated using the correct checksum algorithm and accounts for the
* logical I/O size and not just a gang fragment.
*/
valid_cksum = (zio_checksum_error_impl(zio->io_spa, zio->io_bp,
BP_GET_CHECKSUM(zio->io_bp), zio->io_data, zio->io_size,
zio->io_offset, NULL) == 0);
zio_pop_transforms(zio);
return (valid_cksum);
}
/*
* Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a
* checksum and attaches it to the buf's hdr so that we can ensure that the buf
* isn't modified later on. If buf is compressed or there is already a checksum
* on the hdr, this is a no-op (we only checksum uncompressed bufs).
*/
static void
arc_cksum_compute(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
if (!(zfs_flags & ZFS_DEBUG_MODIFY))
return;
ASSERT(HDR_HAS_L1HDR(hdr));
mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
ASSERT(arc_hdr_has_uncompressed_buf(hdr));
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
return;
} else if (ARC_BUF_COMPRESSED(buf)) {
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
return;
}
ASSERT(!ARC_BUF_COMPRESSED(buf));
hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t),
KM_SLEEP);
fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL,
hdr->b_l1hdr.b_freeze_cksum);
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
#ifdef illumos
arc_buf_watch(buf);
#endif
}
#ifdef illumos
#ifndef _KERNEL
typedef struct procctl {
long cmd;
prwatch_t prwatch;
} procctl_t;
#endif
/* ARGSUSED */
static void
arc_buf_unwatch(arc_buf_t *buf)
{
#ifndef _KERNEL
if (arc_watch) {
int result;
procctl_t ctl;
ctl.cmd = PCWATCH;
ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
ctl.prwatch.pr_size = 0;
ctl.prwatch.pr_wflags = 0;
result = write(arc_procfd, &ctl, sizeof (ctl));
ASSERT3U(result, ==, sizeof (ctl));
}
#endif
}
/* ARGSUSED */
static void
arc_buf_watch(arc_buf_t *buf)
{
#ifndef _KERNEL
if (arc_watch) {
int result;
procctl_t ctl;
ctl.cmd = PCWATCH;
ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
ctl.prwatch.pr_size = arc_buf_size(buf);
ctl.prwatch.pr_wflags = WA_WRITE;
result = write(arc_procfd, &ctl, sizeof (ctl));
ASSERT3U(result, ==, sizeof (ctl));
}
#endif
}
#endif /* illumos */
static arc_buf_contents_t
arc_buf_type(arc_buf_hdr_t *hdr)
{
arc_buf_contents_t type;
if (HDR_ISTYPE_METADATA(hdr)) {
type = ARC_BUFC_METADATA;
} else {
type = ARC_BUFC_DATA;
}
VERIFY3U(hdr->b_type, ==, type);
return (type);
}
boolean_t
arc_is_metadata(arc_buf_t *buf)
{
return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0);
}
static uint32_t
arc_bufc_to_flags(arc_buf_contents_t type)
{
switch (type) {
case ARC_BUFC_DATA:
/* metadata field is 0 if buffer contains normal data */
return (0);
case ARC_BUFC_METADATA:
return (ARC_FLAG_BUFC_METADATA);
default:
break;
}
panic("undefined ARC buffer type!");
return ((uint32_t)-1);
}
void
arc_buf_thaw(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
arc_cksum_verify(buf);
/*
* Compressed buffers do not manipulate the b_freeze_cksum or
* allocate b_thawed.
*/
if (ARC_BUF_COMPRESSED(buf)) {
ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
arc_hdr_has_uncompressed_buf(hdr));
return;
}
ASSERT(HDR_HAS_L1HDR(hdr));
arc_cksum_free(hdr);
mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
#ifdef ZFS_DEBUG
if (zfs_flags & ZFS_DEBUG_MODIFY) {
if (hdr->b_l1hdr.b_thawed != NULL)
kmem_free(hdr->b_l1hdr.b_thawed, 1);
hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP);
}
#endif
mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
#ifdef illumos
arc_buf_unwatch(buf);
#endif
}
void
arc_buf_freeze(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
kmutex_t *hash_lock;
if (!(zfs_flags & ZFS_DEBUG_MODIFY))
return;
if (ARC_BUF_COMPRESSED(buf)) {
ASSERT(hdr->b_l1hdr.b_freeze_cksum == NULL ||
arc_hdr_has_uncompressed_buf(hdr));
return;
}
hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(hdr->b_l1hdr.b_freeze_cksum != NULL ||
hdr->b_l1hdr.b_state == arc_anon);
arc_cksum_compute(buf);
mutex_exit(hash_lock);
}
/*
* The arc_buf_hdr_t's b_flags should never be modified directly. Instead,
* the following functions should be used to ensure that the flags are
* updated in a thread-safe way. When manipulating the flags either
* the hash_lock must be held or the hdr must be undiscoverable. This
* ensures that we're not racing with any other threads when updating
* the flags.
*/
static inline void
arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
{
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
hdr->b_flags |= flags;
}
static inline void
arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
{
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
hdr->b_flags &= ~flags;
}
/*
* Setting the compression bits in the arc_buf_hdr_t's b_flags is
* done in a special way since we have to clear and set bits
* at the same time. Consumers that wish to set the compression bits
* must use this function to ensure that the flags are updated in
* thread-safe manner.
*/
static void
arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp)
{
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
/*
* Holes and embedded blocks will always have a psize = 0 so
* we ignore the compression of the blkptr and set the
* arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF.
* Holes and embedded blocks remain anonymous so we don't
* want to uncompress them. Mark them as uncompressed.
*/
if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) {
arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
HDR_SET_COMPRESS(hdr, ZIO_COMPRESS_OFF);
ASSERT(!HDR_COMPRESSION_ENABLED(hdr));
ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
} else {
arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
HDR_SET_COMPRESS(hdr, cmp);
ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp);
ASSERT(HDR_COMPRESSION_ENABLED(hdr));
}
}
/*
* Looks for another buf on the same hdr which has the data decompressed, copies
* from it, and returns true. If no such buf exists, returns false.
*/
static boolean_t
arc_buf_try_copy_decompressed_data(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
boolean_t copied = B_FALSE;
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT3P(buf->b_data, !=, NULL);
ASSERT(!ARC_BUF_COMPRESSED(buf));
for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL;
from = from->b_next) {
/* can't use our own data buffer */
if (from == buf) {
continue;
}
if (!ARC_BUF_COMPRESSED(from)) {
bcopy(from->b_data, buf->b_data, arc_buf_size(buf));
copied = B_TRUE;
break;
}
}
/*
* There were no decompressed bufs, so there should not be a
* checksum on the hdr either.
*/
EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL);
return (copied);
}
/*
* Given a buf that has a data buffer attached to it, this function will
* efficiently fill the buf with data of the specified compression setting from
* the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr
* are already sharing a data buf, no copy is performed.
*
* If the buf is marked as compressed but uncompressed data was requested, this
* will allocate a new data buffer for the buf, remove that flag, and fill the
* buf with uncompressed data. You can't request a compressed buf on a hdr with
* uncompressed data, and (since we haven't added support for it yet) if you
* want compressed data your buf must already be marked as compressed and have
* the correct-sized data buffer.
*/
static int
arc_buf_fill(arc_buf_t *buf, boolean_t compressed)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
boolean_t hdr_compressed = (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap;
ASSERT3P(buf->b_data, !=, NULL);
IMPLY(compressed, hdr_compressed);
IMPLY(compressed, ARC_BUF_COMPRESSED(buf));
if (hdr_compressed == compressed) {
if (!arc_buf_is_shared(buf)) {
bcopy(hdr->b_l1hdr.b_pdata, buf->b_data,
arc_buf_size(buf));
}
} else {
ASSERT(hdr_compressed);
ASSERT(!compressed);
ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr));
/*
* If the buf is sharing its data with the hdr, unlink it and
* allocate a new data buffer for the buf.
*/
if (arc_buf_is_shared(buf)) {
ASSERT(ARC_BUF_COMPRESSED(buf));
/* We need to give the buf it's own b_data */
buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
buf->b_data =
arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
/* Previously overhead was 0; just add new overhead */
ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr));
} else if (ARC_BUF_COMPRESSED(buf)) {
/* We need to reallocate the buf's b_data */
arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr),
buf);
buf->b_data =
arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
/* We increased the size of b_data; update overhead */
ARCSTAT_INCR(arcstat_overhead_size,
HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr));
}
/*
* Regardless of the buf's previous compression settings, it
* should not be compressed at the end of this function.
*/
buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
/*
* Try copying the data from another buf which already has a
* decompressed version. If that's not possible, it's time to
* bite the bullet and decompress the data from the hdr.
*/
if (arc_buf_try_copy_decompressed_data(buf)) {
/* Skip byteswapping and checksumming (already done) */
ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL);
return (0);
} else {
int error = zio_decompress_data(HDR_GET_COMPRESS(hdr),
hdr->b_l1hdr.b_pdata, buf->b_data,
HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
/*
* Absent hardware errors or software bugs, this should
* be impossible, but log it anyway so we can debug it.
*/
if (error != 0) {
zfs_dbgmsg(
"hdr %p, compress %d, psize %d, lsize %d",
hdr, HDR_GET_COMPRESS(hdr),
HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
return (SET_ERROR(EIO));
}
}
}
/* Byteswap the buf's data if necessary */
if (bswap != DMU_BSWAP_NUMFUNCS) {
ASSERT(!HDR_SHARED_DATA(hdr));
ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS);
dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr));
}
/* Compute the hdr's checksum if necessary */
arc_cksum_compute(buf);
return (0);
}
int
arc_decompress(arc_buf_t *buf)
{
return (arc_buf_fill(buf, B_FALSE));
}
/*
* Return the size of the block, b_pdata, that is stored in the arc_buf_hdr_t.
*/
static uint64_t
arc_hdr_size(arc_buf_hdr_t *hdr)
{
uint64_t size;
if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
HDR_GET_PSIZE(hdr) > 0) {
size = HDR_GET_PSIZE(hdr);
} else {
ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0);
size = HDR_GET_LSIZE(hdr);
}
return (size);
}
/*
* Increment the amount of evictable space in the arc_state_t's refcount.
* We account for the space used by the hdr and the arc buf individually
* so that we can add and remove them from the refcount individually.
*/
static void
arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state)
{
arc_buf_contents_t type = arc_buf_type(hdr);
ASSERT(HDR_HAS_L1HDR(hdr));
if (GHOST_STATE(state)) {
ASSERT0(hdr->b_l1hdr.b_bufcnt);
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL);
(void) refcount_add_many(&state->arcs_esize[type],
HDR_GET_LSIZE(hdr), hdr);
return;
}
ASSERT(!GHOST_STATE(state));
if (hdr->b_l1hdr.b_pdata != NULL) {
(void) refcount_add_many(&state->arcs_esize[type],
arc_hdr_size(hdr), hdr);
}
for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
buf = buf->b_next) {
if (arc_buf_is_shared(buf))
continue;
(void) refcount_add_many(&state->arcs_esize[type],
arc_buf_size(buf), buf);
}
}
/*
* Decrement the amount of evictable space in the arc_state_t's refcount.
* We account for the space used by the hdr and the arc buf individually
* so that we can add and remove them from the refcount individually.
*/
static void
arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state)
{
arc_buf_contents_t type = arc_buf_type(hdr);
ASSERT(HDR_HAS_L1HDR(hdr));
if (GHOST_STATE(state)) {
ASSERT0(hdr->b_l1hdr.b_bufcnt);
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL);
(void) refcount_remove_many(&state->arcs_esize[type],
HDR_GET_LSIZE(hdr), hdr);
return;
}
ASSERT(!GHOST_STATE(state));
if (hdr->b_l1hdr.b_pdata != NULL) {
(void) refcount_remove_many(&state->arcs_esize[type],
arc_hdr_size(hdr), hdr);
}
for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
buf = buf->b_next) {
if (arc_buf_is_shared(buf))
continue;
(void) refcount_remove_many(&state->arcs_esize[type],
arc_buf_size(buf), buf);
}
}
/*
* Add a reference to this hdr indicating that someone is actively
* referencing that memory. When the refcount transitions from 0 to 1,
* we remove it from the respective arc_state_t list to indicate that
* it is not evictable.
*/
static void
add_reference(arc_buf_hdr_t *hdr, void *tag)
{
ASSERT(HDR_HAS_L1HDR(hdr));
if (!MUTEX_HELD(HDR_LOCK(hdr))) {
ASSERT(hdr->b_l1hdr.b_state == arc_anon);
ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
}
arc_state_t *state = hdr->b_l1hdr.b_state;
if ((refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
(state != arc_anon)) {
/* We don't use the L2-only state list. */
if (state != arc_l2c_only) {
multilist_remove(state->arcs_list[arc_buf_type(hdr)],
hdr);
arc_evictable_space_decrement(hdr, state);
}
/* remove the prefetch flag if we get a reference */
arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
}
}
/*
* Remove a reference from this hdr. When the reference transitions from
* 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's
* list making it eligible for eviction.
*/
static int
remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
{
int cnt;
arc_state_t *state = hdr->b_l1hdr.b_state;
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
ASSERT(!GHOST_STATE(state));
/*
* arc_l2c_only counts as a ghost state so we don't need to explicitly
* check to prevent usage of the arc_l2c_only list.
*/
if (((cnt = refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
(state != arc_anon)) {
multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr);
ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
arc_evictable_space_increment(hdr, state);
}
return (cnt);
}
/*
* Move the supplied buffer to the indicated state. The hash lock
* for the buffer must be held by the caller.
*/
static void
arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
kmutex_t *hash_lock)
{
arc_state_t *old_state;
int64_t refcnt;
uint32_t bufcnt;
boolean_t update_old, update_new;
arc_buf_contents_t buftype = arc_buf_type(hdr);
/*
* We almost always have an L1 hdr here, since we call arc_hdr_realloc()
* in arc_read() when bringing a buffer out of the L2ARC. However, the
* L1 hdr doesn't always exist when we change state to arc_anon before
* destroying a header, in which case reallocating to add the L1 hdr is
* pointless.
*/
if (HDR_HAS_L1HDR(hdr)) {
old_state = hdr->b_l1hdr.b_state;
refcnt = refcount_count(&hdr->b_l1hdr.b_refcnt);
bufcnt = hdr->b_l1hdr.b_bufcnt;
update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pdata != NULL);
} else {
old_state = arc_l2c_only;
refcnt = 0;
bufcnt = 0;
update_old = B_FALSE;
}
update_new = update_old;
ASSERT(MUTEX_HELD(hash_lock));
ASSERT3P(new_state, !=, old_state);
ASSERT(!GHOST_STATE(new_state) || bufcnt == 0);
ASSERT(old_state != arc_anon || bufcnt <= 1);
/*
* If this buffer is evictable, transfer it from the
* old state list to the new state list.
*/
if (refcnt == 0) {
if (old_state != arc_anon && old_state != arc_l2c_only) {
ASSERT(HDR_HAS_L1HDR(hdr));
multilist_remove(old_state->arcs_list[buftype], hdr);
if (GHOST_STATE(old_state)) {
ASSERT0(bufcnt);
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
update_old = B_TRUE;
}
arc_evictable_space_decrement(hdr, old_state);
}
if (new_state != arc_anon && new_state != arc_l2c_only) {
/*
* An L1 header always exists here, since if we're
* moving to some L1-cached state (i.e. not l2c_only or
* anonymous), we realloc the header to add an L1hdr
* beforehand.
*/
ASSERT(HDR_HAS_L1HDR(hdr));
multilist_insert(new_state->arcs_list[buftype], hdr);
if (GHOST_STATE(new_state)) {
ASSERT0(bufcnt);
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
update_new = B_TRUE;
}
arc_evictable_space_increment(hdr, new_state);
}
}
ASSERT(!HDR_EMPTY(hdr));
if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
buf_hash_remove(hdr);
/* adjust state sizes (ignore arc_l2c_only) */
if (update_new && new_state != arc_l2c_only) {
ASSERT(HDR_HAS_L1HDR(hdr));
if (GHOST_STATE(new_state)) {
ASSERT0(bufcnt);
/*
* When moving a header to a ghost state, we first
* remove all arc buffers. Thus, we'll have a
* bufcnt of zero, and no arc buffer to use for
* the reference. As a result, we use the arc
* header pointer for the reference.
*/
(void) refcount_add_many(&new_state->arcs_size,
HDR_GET_LSIZE(hdr), hdr);
ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL);
} else {
uint32_t buffers = 0;
/*
* Each individual buffer holds a unique reference,
* thus we must remove each of these references one
* at a time.
*/
for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
buf = buf->b_next) {
ASSERT3U(bufcnt, !=, 0);
buffers++;
/*
* When the arc_buf_t is sharing the data
* block with the hdr, the owner of the
* reference belongs to the hdr. Only
* add to the refcount if the arc_buf_t is
* not shared.
*/
if (arc_buf_is_shared(buf))
continue;
(void) refcount_add_many(&new_state->arcs_size,
arc_buf_size(buf), buf);
}
ASSERT3U(bufcnt, ==, buffers);
if (hdr->b_l1hdr.b_pdata != NULL) {
(void) refcount_add_many(&new_state->arcs_size,
arc_hdr_size(hdr), hdr);
} else {
ASSERT(GHOST_STATE(old_state));
}
}
}
if (update_old && old_state != arc_l2c_only) {
ASSERT(HDR_HAS_L1HDR(hdr));
if (GHOST_STATE(old_state)) {
ASSERT0(bufcnt);
ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL);
/*
* When moving a header off of a ghost state,
* the header will not contain any arc buffers.
* We use the arc header pointer for the reference
* which is exactly what we did when we put the
* header on the ghost state.
*/
(void) refcount_remove_many(&old_state->arcs_size,
HDR_GET_LSIZE(hdr), hdr);
} else {
uint32_t buffers = 0;
/*
* Each individual buffer holds a unique reference,
* thus we must remove each of these references one
* at a time.
*/
for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
buf = buf->b_next) {
ASSERT3U(bufcnt, !=, 0);
buffers++;
/*
* When the arc_buf_t is sharing the data
* block with the hdr, the owner of the
* reference belongs to the hdr. Only
* add to the refcount if the arc_buf_t is
* not shared.
*/
if (arc_buf_is_shared(buf))
continue;
(void) refcount_remove_many(
&old_state->arcs_size, arc_buf_size(buf),
buf);
}
ASSERT3U(bufcnt, ==, buffers);
ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL);
(void) refcount_remove_many(
&old_state->arcs_size, arc_hdr_size(hdr), hdr);
}
}
if (HDR_HAS_L1HDR(hdr))
hdr->b_l1hdr.b_state = new_state;
/*
* L2 headers should never be on the L2 state list since they don't
* have L1 headers allocated.
*/
ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) &&
multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
}
void
arc_space_consume(uint64_t space, arc_space_type_t type)
{
ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
switch (type) {
case ARC_SPACE_DATA:
ARCSTAT_INCR(arcstat_data_size, space);
break;
case ARC_SPACE_META:
ARCSTAT_INCR(arcstat_metadata_size, space);
break;
case ARC_SPACE_OTHER:
ARCSTAT_INCR(arcstat_other_size, space);
break;
case ARC_SPACE_HDRS:
ARCSTAT_INCR(arcstat_hdr_size, space);
break;
case ARC_SPACE_L2HDRS:
ARCSTAT_INCR(arcstat_l2_hdr_size, space);
break;
}
if (type != ARC_SPACE_DATA)
ARCSTAT_INCR(arcstat_meta_used, space);
atomic_add_64(&arc_size, space);
}
void
arc_space_return(uint64_t space, arc_space_type_t type)
{
ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
switch (type) {
case ARC_SPACE_DATA:
ARCSTAT_INCR(arcstat_data_size, -space);
break;
case ARC_SPACE_META:
ARCSTAT_INCR(arcstat_metadata_size, -space);
break;
case ARC_SPACE_OTHER:
ARCSTAT_INCR(arcstat_other_size, -space);
break;
case ARC_SPACE_HDRS:
ARCSTAT_INCR(arcstat_hdr_size, -space);
break;
case ARC_SPACE_L2HDRS:
ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
break;
}
if (type != ARC_SPACE_DATA) {
ASSERT(arc_meta_used >= space);
if (arc_meta_max < arc_meta_used)
arc_meta_max = arc_meta_used;
ARCSTAT_INCR(arcstat_meta_used, -space);
}
ASSERT(arc_size >= space);
atomic_add_64(&arc_size, -space);
}
/*
* Given a hdr and a buf, returns whether that buf can share its b_data buffer
* with the hdr's b_pdata.
*/
static boolean_t
arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf)
{
/*
* The criteria for sharing a hdr's data are:
* 1. the hdr's compression matches the buf's compression
* 2. the hdr doesn't need to be byteswapped
* 3. the hdr isn't already being shared
* 4. the buf is either compressed or it is the last buf in the hdr list
*
* Criterion #4 maintains the invariant that shared uncompressed
* bufs must be the final buf in the hdr's b_buf list. Reading this, you
* might ask, "if a compressed buf is allocated first, won't that be the
* last thing in the list?", but in that case it's impossible to create
* a shared uncompressed buf anyway (because the hdr must be compressed
* to have the compressed buf). You might also think that #3 is
* sufficient to make this guarantee, however it's possible
* (specifically in the rare L2ARC write race mentioned in
* arc_buf_alloc_impl()) there will be an existing uncompressed buf that
* is sharable, but wasn't at the time of its allocation. Rather than
* allow a new shared uncompressed buf to be created and then shuffle
* the list around to make it the last element, this simply disallows
* sharing if the new buf isn't the first to be added.
*/
ASSERT3P(buf->b_hdr, ==, hdr);
boolean_t hdr_compressed = HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF;
boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0;
return (buf_compressed == hdr_compressed &&
hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS &&
!HDR_SHARED_DATA(hdr) &&
(ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf)));
}
/*
* Allocate a buf for this hdr. If you care about the data that's in the hdr,
* or if you want a compressed buffer, pass those flags in. Returns 0 if the
* copy was made successfully, or an error code otherwise.
*/
static int
arc_buf_alloc_impl(arc_buf_hdr_t *hdr, void *tag, boolean_t compressed,
boolean_t fill, arc_buf_t **ret)
{
arc_buf_t *buf;
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
VERIFY(hdr->b_type == ARC_BUFC_DATA ||
hdr->b_type == ARC_BUFC_METADATA);
ASSERT3P(ret, !=, NULL);
ASSERT3P(*ret, ==, NULL);
buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
buf->b_hdr = hdr;
buf->b_data = NULL;
buf->b_next = hdr->b_l1hdr.b_buf;
buf->b_flags = 0;
add_reference(hdr, tag);
/*
* We're about to change the hdr's b_flags. We must either
* hold the hash_lock or be undiscoverable.
*/
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
/*
* Only honor requests for compressed bufs if the hdr is actually
* compressed.
*/
if (compressed && HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF)
buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
/*
* If the hdr's data can be shared then we share the data buffer and
* set the appropriate bit in the hdr's b_flags to indicate the hdr is
* sharing it's b_pdata with the arc_buf_t. Otherwise, we allocate a new
* buffer to store the buf's data.
*
* There is one additional restriction here because we're sharing
* hdr -> buf instead of the usual buf -> hdr: the hdr can't be actively
* involved in an L2ARC write, because if this buf is used by an
* arc_write() then the hdr's data buffer will be released when the
* write completes, even though the L2ARC write might still be using it.
*/
boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr);
/* Set up b_data and sharing */
if (can_share) {
buf->b_data = hdr->b_l1hdr.b_pdata;
buf->b_flags |= ARC_BUF_FLAG_SHARED;
arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
} else {
buf->b_data =
arc_get_data_buf(hdr, arc_buf_size(buf), buf);
ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
}
VERIFY3P(buf->b_data, !=, NULL);
hdr->b_l1hdr.b_buf = buf;
hdr->b_l1hdr.b_bufcnt += 1;
/*
* If the user wants the data from the hdr, we need to either copy or
* decompress the data.
*/
if (fill) {
return (arc_buf_fill(buf, ARC_BUF_COMPRESSED(buf) != 0));
}
return (0);
}
static char *arc_onloan_tag = "onloan";
static inline void
arc_loaned_bytes_update(int64_t delta)
{
atomic_add_64(&arc_loaned_bytes, delta);
/* assert that it did not wrap around */
ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
}
/*
* Loan out an anonymous arc buffer. Loaned buffers are not counted as in
* flight data by arc_tempreserve_space() until they are "returned". Loaned
* buffers must be returned to the arc before they can be used by the DMU or
* freed.
*/
arc_buf_t *
arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size)
{
arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag,
is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size);
arc_loaned_bytes_update(size);
return (buf);
}
arc_buf_t *
arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize,
enum zio_compress compression_type)
{
arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag,
psize, lsize, compression_type);
arc_loaned_bytes_update(psize);
return (buf);
}
/*
* Return a loaned arc buffer to the arc.
*/
void
arc_return_buf(arc_buf_t *buf, void *tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT3P(buf->b_data, !=, NULL);
ASSERT(HDR_HAS_L1HDR(hdr));
(void) refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
(void) refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
arc_loaned_bytes_update(-arc_buf_size(buf));
}
/* Detach an arc_buf from a dbuf (tag) */
void
arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT3P(buf->b_data, !=, NULL);
ASSERT(HDR_HAS_L1HDR(hdr));
(void) refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
(void) refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
arc_loaned_bytes_update(arc_buf_size(buf));
}
static void
l2arc_free_data_on_write(void *data, size_t size, arc_buf_contents_t type)
{
l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP);
df->l2df_data = data;
df->l2df_size = size;
df->l2df_type = type;
mutex_enter(&l2arc_free_on_write_mtx);
list_insert_head(l2arc_free_on_write, df);
mutex_exit(&l2arc_free_on_write_mtx);
}
static void
arc_hdr_free_on_write(arc_buf_hdr_t *hdr)
{
arc_state_t *state = hdr->b_l1hdr.b_state;
arc_buf_contents_t type = arc_buf_type(hdr);
uint64_t size = arc_hdr_size(hdr);
/* protected by hash lock, if in the hash table */
if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
ASSERT(state != arc_anon && state != arc_l2c_only);
(void) refcount_remove_many(&state->arcs_esize[type],
size, hdr);
}
(void) refcount_remove_many(&state->arcs_size, size, hdr);
if (type == ARC_BUFC_METADATA) {
arc_space_return(size, ARC_SPACE_META);
} else {
ASSERT(type == ARC_BUFC_DATA);
arc_space_return(size, ARC_SPACE_DATA);
}
l2arc_free_data_on_write(hdr->b_l1hdr.b_pdata, size, type);
}
/*
* Share the arc_buf_t's data with the hdr. Whenever we are sharing the
* data buffer, we transfer the refcount ownership to the hdr and update
* the appropriate kstats.
*/
static void
arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
{
arc_state_t *state = hdr->b_l1hdr.b_state;
ASSERT(arc_can_share(hdr, buf));
ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL);
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
/*
* Start sharing the data buffer. We transfer the
* refcount ownership to the hdr since it always owns
* the refcount whenever an arc_buf_t is shared.
*/
refcount_transfer_ownership(&state->arcs_size, buf, hdr);
hdr->b_l1hdr.b_pdata = buf->b_data;
arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
buf->b_flags |= ARC_BUF_FLAG_SHARED;
/*
* Since we've transferred ownership to the hdr we need
* to increment its compressed and uncompressed kstats and
* decrement the overhead size.
*/
ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf));
}
static void
arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
{
arc_state_t *state = hdr->b_l1hdr.b_state;
ASSERT(arc_buf_is_shared(buf));
ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL);
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
/*
* We are no longer sharing this buffer so we need
* to transfer its ownership to the rightful owner.
*/
refcount_transfer_ownership(&state->arcs_size, hdr, buf);
arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
hdr->b_l1hdr.b_pdata = NULL;
buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
/*
* Since the buffer is no longer shared between
* the arc buf and the hdr, count it as overhead.
*/
ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
}
/*
* Remove an arc_buf_t from the hdr's buf list and return the last
* arc_buf_t on the list. If no buffers remain on the list then return
* NULL.
*/
static arc_buf_t *
arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf)
{
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
arc_buf_t **bufp = &hdr->b_l1hdr.b_buf;
arc_buf_t *lastbuf = NULL;
/*
* Remove the buf from the hdr list and locate the last
* remaining buffer on the list.
*/
while (*bufp != NULL) {
if (*bufp == buf)
*bufp = buf->b_next;
/*
* If we've removed a buffer in the middle of
* the list then update the lastbuf and update
* bufp.
*/
if (*bufp != NULL) {
lastbuf = *bufp;
bufp = &(*bufp)->b_next;
}
}
buf->b_next = NULL;
ASSERT3P(lastbuf, !=, buf);
IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL);
IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL);
IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf));
return (lastbuf);
}
/*
* Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's
* list and free it.
*/
static void
arc_buf_destroy_impl(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
/*
* Free up the data associated with the buf but only if we're not
* sharing this with the hdr. If we are sharing it with the hdr, the
* hdr is responsible for doing the free.
*/
if (buf->b_data != NULL) {
/*
* We're about to change the hdr's b_flags. We must either
* hold the hash_lock or be undiscoverable.
*/
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)) || HDR_EMPTY(hdr));
arc_cksum_verify(buf);
#ifdef illumos
arc_buf_unwatch(buf);
#endif
if (arc_buf_is_shared(buf)) {
arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
} else {
uint64_t size = arc_buf_size(buf);
arc_free_data_buf(hdr, buf->b_data, size, buf);
ARCSTAT_INCR(arcstat_overhead_size, -size);
}
buf->b_data = NULL;
ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
hdr->b_l1hdr.b_bufcnt -= 1;
}
arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) {
/*
* If the current arc_buf_t is sharing its data buffer with the
* hdr, then reassign the hdr's b_pdata to share it with the new
* buffer at the end of the list. The shared buffer is always
* the last one on the hdr's buffer list.
*
* There is an equivalent case for compressed bufs, but since
* they aren't guaranteed to be the last buf in the list and
* that is an exceedingly rare case, we just allow that space be
* wasted temporarily.
*/
if (lastbuf != NULL) {
/* Only one buf can be shared at once */
VERIFY(!arc_buf_is_shared(lastbuf));
/* hdr is uncompressed so can't have compressed buf */
VERIFY(!ARC_BUF_COMPRESSED(lastbuf));
ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL);
arc_hdr_free_pdata(hdr);
/*
* We must setup a new shared block between the
* last buffer and the hdr. The data would have
* been allocated by the arc buf so we need to transfer
* ownership to the hdr since it's now being shared.
*/
arc_share_buf(hdr, lastbuf);
}
} else if (HDR_SHARED_DATA(hdr)) {
/*
* Uncompressed shared buffers are always at the end
* of the list. Compressed buffers don't have the
* same requirements. This makes it hard to
* simply assert that the lastbuf is shared so
* we rely on the hdr's compression flags to determine
* if we have a compressed, shared buffer.
*/
ASSERT3P(lastbuf, !=, NULL);
ASSERT(arc_buf_is_shared(lastbuf) ||
HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
}
/*
* Free the checksum if we're removing the last uncompressed buf from
* this hdr.
*/
if (!arc_hdr_has_uncompressed_buf(hdr)) {
arc_cksum_free(hdr);
}
/* clean up the buf */
buf->b_hdr = NULL;
kmem_cache_free(buf_cache, buf);
}
static void
arc_hdr_alloc_pdata(arc_buf_hdr_t *hdr)
{
ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(!HDR_SHARED_DATA(hdr));
ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL);
hdr->b_l1hdr.b_pdata = arc_get_data_buf(hdr, arc_hdr_size(hdr), hdr);
hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL);
ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
}
static void
arc_hdr_free_pdata(arc_buf_hdr_t *hdr)
{
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL);
/*
* If the hdr is currently being written to the l2arc then
* we defer freeing the data by adding it to the l2arc_free_on_write
* list. The l2arc will free the data once it's finished
* writing it to the l2arc device.
*/
if (HDR_L2_WRITING(hdr)) {
arc_hdr_free_on_write(hdr);
ARCSTAT_BUMP(arcstat_l2_free_on_write);
} else {
arc_free_data_buf(hdr, hdr->b_l1hdr.b_pdata,
arc_hdr_size(hdr), hdr);
}
hdr->b_l1hdr.b_pdata = NULL;
hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
}
static arc_buf_hdr_t *
arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize,
enum zio_compress compression_type, arc_buf_contents_t type)
{
arc_buf_hdr_t *hdr;
VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA);
hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
ASSERT(HDR_EMPTY(hdr));
ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL);
HDR_SET_PSIZE(hdr, psize);
HDR_SET_LSIZE(hdr, lsize);
hdr->b_spa = spa;
hdr->b_type = type;
hdr->b_flags = 0;
arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR);
arc_hdr_set_compress(hdr, compression_type);
hdr->b_l1hdr.b_state = arc_anon;
hdr->b_l1hdr.b_arc_access = 0;
hdr->b_l1hdr.b_bufcnt = 0;
hdr->b_l1hdr.b_buf = NULL;
/*
* Allocate the hdr's buffer. This will contain either
* the compressed or uncompressed data depending on the block
* it references and compressed arc enablement.
*/
arc_hdr_alloc_pdata(hdr);
ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
return (hdr);
}
/*
* Transition between the two allocation states for the arc_buf_hdr struct.
* The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
* (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
* version is used when a cache buffer is only in the L2ARC in order to reduce
* memory usage.
*/
static arc_buf_hdr_t *
arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
{
ASSERT(HDR_HAS_L2HDR(hdr));
arc_buf_hdr_t *nhdr;
l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
(old == hdr_l2only_cache && new == hdr_full_cache));
nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
buf_hash_remove(hdr);
bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
if (new == hdr_full_cache) {
arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR);
/*
* arc_access and arc_change_state need to be aware that a
* header has just come out of L2ARC, so we set its state to
* l2c_only even though it's about to change.
*/
nhdr->b_l1hdr.b_state = arc_l2c_only;
/* Verify previous threads set to NULL before freeing */
ASSERT3P(nhdr->b_l1hdr.b_pdata, ==, NULL);
} else {
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
ASSERT0(hdr->b_l1hdr.b_bufcnt);
ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
/*
* If we've reached here, We must have been called from
* arc_evict_hdr(), as such we should have already been
* removed from any ghost list we were previously on
* (which protects us from racing with arc_evict_state),
* thus no locking is needed during this check.
*/
ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
/*
* A buffer must not be moved into the arc_l2c_only
* state if it's not finished being written out to the
* l2arc device. Otherwise, the b_l1hdr.b_pdata field
* might try to be accessed, even though it was removed.
*/
VERIFY(!HDR_L2_WRITING(hdr));
VERIFY3P(hdr->b_l1hdr.b_pdata, ==, NULL);
#ifdef ZFS_DEBUG
if (hdr->b_l1hdr.b_thawed != NULL) {
kmem_free(hdr->b_l1hdr.b_thawed, 1);
hdr->b_l1hdr.b_thawed = NULL;
}
#endif
arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR);
}
/*
* The header has been reallocated so we need to re-insert it into any
* lists it was on.
*/
(void) buf_hash_insert(nhdr, NULL);
ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
mutex_enter(&dev->l2ad_mtx);
/*
* We must place the realloc'ed header back into the list at
* the same spot. Otherwise, if it's placed earlier in the list,
* l2arc_write_buffers() could find it during the function's
* write phase, and try to write it out to the l2arc.
*/
list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
list_remove(&dev->l2ad_buflist, hdr);
mutex_exit(&dev->l2ad_mtx);
/*
* Since we're using the pointer address as the tag when
* incrementing and decrementing the l2ad_alloc refcount, we
* must remove the old pointer (that we're about to destroy) and
* add the new pointer to the refcount. Otherwise we'd remove
* the wrong pointer address when calling arc_hdr_destroy() later.
*/
(void) refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr);
(void) refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr), nhdr);
buf_discard_identity(hdr);
kmem_cache_free(old, hdr);
return (nhdr);
}
/*
* Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller.
* The buf is returned thawed since we expect the consumer to modify it.
*/
arc_buf_t *
arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size)
{
arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size,
ZIO_COMPRESS_OFF, type);
ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
arc_buf_t *buf = NULL;
VERIFY0(arc_buf_alloc_impl(hdr, tag, B_FALSE, B_FALSE, &buf));
arc_buf_thaw(buf);
return (buf);
}
/*
* Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this
* for bufs containing metadata.
*/
arc_buf_t *
arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize,
enum zio_compress compression_type)
{
ASSERT3U(lsize, >, 0);
ASSERT3U(lsize, >=, psize);
ASSERT(compression_type > ZIO_COMPRESS_OFF);
ASSERT(compression_type < ZIO_COMPRESS_FUNCTIONS);
arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
compression_type, ARC_BUFC_DATA);
ASSERT(!MUTEX_HELD(HDR_LOCK(hdr)));
arc_buf_t *buf = NULL;
VERIFY0(arc_buf_alloc_impl(hdr, tag, B_TRUE, B_FALSE, &buf));
arc_buf_thaw(buf);
ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
return (buf);
}
static void
arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
{
l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
l2arc_dev_t *dev = l2hdr->b_dev;
uint64_t asize = arc_hdr_size(hdr);
ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
ASSERT(HDR_HAS_L2HDR(hdr));
list_remove(&dev->l2ad_buflist, hdr);
ARCSTAT_INCR(arcstat_l2_asize, -asize);
ARCSTAT_INCR(arcstat_l2_size, -HDR_GET_LSIZE(hdr));
vdev_space_update(dev->l2ad_vdev, -asize, 0, 0);
(void) refcount_remove_many(&dev->l2ad_alloc, asize, hdr);
arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
}
static void
arc_hdr_destroy(arc_buf_hdr_t *hdr)
{
if (HDR_HAS_L1HDR(hdr)) {
ASSERT(hdr->b_l1hdr.b_buf == NULL ||
hdr->b_l1hdr.b_bufcnt > 0);
ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
}
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
ASSERT(!HDR_IN_HASH_TABLE(hdr));
if (!HDR_EMPTY(hdr))
buf_discard_identity(hdr);
if (HDR_HAS_L2HDR(hdr)) {
l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
if (!buflist_held)
mutex_enter(&dev->l2ad_mtx);
/*
* Even though we checked this conditional above, we
* need to check this again now that we have the
* l2ad_mtx. This is because we could be racing with
* another thread calling l2arc_evict() which might have
* destroyed this header's L2 portion as we were waiting
* to acquire the l2ad_mtx. If that happens, we don't
* want to re-destroy the header's L2 portion.
*/
if (HDR_HAS_L2HDR(hdr)) {
l2arc_trim(hdr);
arc_hdr_l2hdr_destroy(hdr);
}
if (!buflist_held)
mutex_exit(&dev->l2ad_mtx);
}
if (HDR_HAS_L1HDR(hdr)) {
arc_cksum_free(hdr);
while (hdr->b_l1hdr.b_buf != NULL)
arc_buf_destroy_impl(hdr->b_l1hdr.b_buf);
#ifdef ZFS_DEBUG
if (hdr->b_l1hdr.b_thawed != NULL) {
kmem_free(hdr->b_l1hdr.b_thawed, 1);
hdr->b_l1hdr.b_thawed = NULL;
}
#endif
if (hdr->b_l1hdr.b_pdata != NULL) {
arc_hdr_free_pdata(hdr);
}
}
ASSERT3P(hdr->b_hash_next, ==, NULL);
if (HDR_HAS_L1HDR(hdr)) {
ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
kmem_cache_free(hdr_full_cache, hdr);
} else {
kmem_cache_free(hdr_l2only_cache, hdr);
}
}
void
arc_buf_destroy(arc_buf_t *buf, void* tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
kmutex_t *hash_lock = HDR_LOCK(hdr);
if (hdr->b_l1hdr.b_state == arc_anon) {
ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
VERIFY0(remove_reference(hdr, NULL, tag));
arc_hdr_destroy(hdr);
return;
}
mutex_enter(hash_lock);
ASSERT3P(hdr, ==, buf->b_hdr);
ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon);
ASSERT3P(buf->b_data, !=, NULL);
(void) remove_reference(hdr, hash_lock, tag);
arc_buf_destroy_impl(buf);
mutex_exit(hash_lock);
}
/*
* Evict the arc_buf_hdr that is provided as a parameter. The resultant
* state of the header is dependent on its state prior to entering this
* function. The following transitions are possible:
*
* - arc_mru -> arc_mru_ghost
* - arc_mfu -> arc_mfu_ghost
* - arc_mru_ghost -> arc_l2c_only
* - arc_mru_ghost -> deleted
* - arc_mfu_ghost -> arc_l2c_only
* - arc_mfu_ghost -> deleted
*/
static int64_t
arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
{
arc_state_t *evicted_state, *state;
int64_t bytes_evicted = 0;
ASSERT(MUTEX_HELD(hash_lock));
ASSERT(HDR_HAS_L1HDR(hdr));
state = hdr->b_l1hdr.b_state;
if (GHOST_STATE(state)) {
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
/*
* l2arc_write_buffers() relies on a header's L1 portion
* (i.e. its b_pdata field) during its write phase.
* Thus, we cannot push a header onto the arc_l2c_only
* state (removing it's L1 piece) until the header is
* done being written to the l2arc.
*/
if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
ARCSTAT_BUMP(arcstat_evict_l2_skip);
return (bytes_evicted);
}
ARCSTAT_BUMP(arcstat_deleted);
bytes_evicted += HDR_GET_LSIZE(hdr);
DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL);
if (HDR_HAS_L2HDR(hdr)) {
/*
* This buffer is cached on the 2nd Level ARC;
* don't destroy the header.
*/
arc_change_state(arc_l2c_only, hdr, hash_lock);
/*
* dropping from L1+L2 cached to L2-only,
* realloc to remove the L1 header.
*/
hdr = arc_hdr_realloc(hdr, hdr_full_cache,
hdr_l2only_cache);
} else {
arc_change_state(arc_anon, hdr, hash_lock);
arc_hdr_destroy(hdr);
}
return (bytes_evicted);
}
ASSERT(state == arc_mru || state == arc_mfu);
evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
/* prefetch buffers have a minimum lifespan */
if (HDR_IO_IN_PROGRESS(hdr) ||
((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access <
arc_min_prefetch_lifespan)) {
ARCSTAT_BUMP(arcstat_evict_skip);
return (bytes_evicted);
}
ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
while (hdr->b_l1hdr.b_buf) {
arc_buf_t *buf = hdr->b_l1hdr.b_buf;
if (!mutex_tryenter(&buf->b_evict_lock)) {
ARCSTAT_BUMP(arcstat_mutex_miss);
break;
}
if (buf->b_data != NULL)
bytes_evicted += HDR_GET_LSIZE(hdr);
mutex_exit(&buf->b_evict_lock);
arc_buf_destroy_impl(buf);
}
if (HDR_HAS_L2HDR(hdr)) {
ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr));
} else {
if (l2arc_write_eligible(hdr->b_spa, hdr)) {
ARCSTAT_INCR(arcstat_evict_l2_eligible,
HDR_GET_LSIZE(hdr));
} else {
ARCSTAT_INCR(arcstat_evict_l2_ineligible,
HDR_GET_LSIZE(hdr));
}
}
if (hdr->b_l1hdr.b_bufcnt == 0) {
arc_cksum_free(hdr);
bytes_evicted += arc_hdr_size(hdr);
/*
* If this hdr is being evicted and has a compressed
* buffer then we discard it here before we change states.
* This ensures that the accounting is updated correctly
* in arc_free_data_buf().
*/
arc_hdr_free_pdata(hdr);
arc_change_state(evicted_state, hdr, hash_lock);
ASSERT(HDR_IN_HASH_TABLE(hdr));
arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
}
return (bytes_evicted);
}
static uint64_t
arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
uint64_t spa, int64_t bytes)
{
multilist_sublist_t *mls;
uint64_t bytes_evicted = 0;
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
int evict_count = 0;
ASSERT3P(marker, !=, NULL);
IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
mls = multilist_sublist_lock(ml, idx);
for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
hdr = multilist_sublist_prev(mls, marker)) {
if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
(evict_count >= zfs_arc_evict_batch_limit))
break;
/*
* To keep our iteration location, move the marker
* forward. Since we're not holding hdr's hash lock, we
* must be very careful and not remove 'hdr' from the
* sublist. Otherwise, other consumers might mistake the
* 'hdr' as not being on a sublist when they call the
* multilist_link_active() function (they all rely on
* the hash lock protecting concurrent insertions and
* removals). multilist_sublist_move_forward() was
* specifically implemented to ensure this is the case
* (only 'marker' will be removed and re-inserted).
*/
multilist_sublist_move_forward(mls, marker);
/*
* The only case where the b_spa field should ever be
* zero, is the marker headers inserted by
* arc_evict_state(). It's possible for multiple threads
* to be calling arc_evict_state() concurrently (e.g.
* dsl_pool_close() and zio_inject_fault()), so we must
* skip any markers we see from these other threads.
*/
if (hdr->b_spa == 0)
continue;
/* we're only interested in evicting buffers of a certain spa */
if (spa != 0 && hdr->b_spa != spa) {
ARCSTAT_BUMP(arcstat_evict_skip);
continue;
}
hash_lock = HDR_LOCK(hdr);
/*
* We aren't calling this function from any code path
* that would already be holding a hash lock, so we're
* asserting on this assumption to be defensive in case
* this ever changes. Without this check, it would be
* possible to incorrectly increment arcstat_mutex_miss
* below (e.g. if the code changed such that we called
* this function with a hash lock held).
*/
ASSERT(!MUTEX_HELD(hash_lock));
if (mutex_tryenter(hash_lock)) {
uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
mutex_exit(hash_lock);
bytes_evicted += evicted;
/*
* If evicted is zero, arc_evict_hdr() must have
* decided to skip this header, don't increment
* evict_count in this case.
*/
if (evicted != 0)
evict_count++;
/*
* If arc_size isn't overflowing, signal any
* threads that might happen to be waiting.
*
* For each header evicted, we wake up a single
* thread. If we used cv_broadcast, we could
* wake up "too many" threads causing arc_size
* to significantly overflow arc_c; since
* arc_get_data_buf() doesn't check for overflow
* when it's woken up (it doesn't because it's
* possible for the ARC to be overflowing while
* full of un-evictable buffers, and the
* function should proceed in this case).
*
* If threads are left sleeping, due to not
* using cv_broadcast, they will be woken up
* just before arc_reclaim_thread() sleeps.
*/
mutex_enter(&arc_reclaim_lock);
if (!arc_is_overflowing())
cv_signal(&arc_reclaim_waiters_cv);
mutex_exit(&arc_reclaim_lock);
} else {
ARCSTAT_BUMP(arcstat_mutex_miss);
}
}
multilist_sublist_unlock(mls);
return (bytes_evicted);
}
/*
* Evict buffers from the given arc state, until we've removed the
* specified number of bytes. Move the removed buffers to the
* appropriate evict state.
*
* This function makes a "best effort". It skips over any buffers
* it can't get a hash_lock on, and so, may not catch all candidates.
* It may also return without evicting as much space as requested.
*
* If bytes is specified using the special value ARC_EVICT_ALL, this
* will evict all available (i.e. unlocked and evictable) buffers from
* the given arc state; which is used by arc_flush().
*/
static uint64_t
arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
arc_buf_contents_t type)
{
uint64_t total_evicted = 0;
multilist_t *ml = state->arcs_list[type];
int num_sublists;
arc_buf_hdr_t **markers;
IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
num_sublists = multilist_get_num_sublists(ml);
/*
* If we've tried to evict from each sublist, made some
* progress, but still have not hit the target number of bytes
* to evict, we want to keep trying. The markers allow us to
* pick up where we left off for each individual sublist, rather
* than starting from the tail each time.
*/
markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
for (int i = 0; i < num_sublists; i++) {
markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
/*
* A b_spa of 0 is used to indicate that this header is
* a marker. This fact is used in arc_adjust_type() and
* arc_evict_state_impl().
*/
markers[i]->b_spa = 0;
multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
multilist_sublist_insert_tail(mls, markers[i]);
multilist_sublist_unlock(mls);
}
/*
* While we haven't hit our target number of bytes to evict, or
* we're evicting all available buffers.
*/
while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
/*
* Start eviction using a randomly selected sublist,
* this is to try and evenly balance eviction across all
* sublists. Always starting at the same sublist
* (e.g. index 0) would cause evictions to favor certain
* sublists over others.
*/
int sublist_idx = multilist_get_random_index(ml);
uint64_t scan_evicted = 0;
for (int i = 0; i < num_sublists; i++) {
uint64_t bytes_remaining;
uint64_t bytes_evicted;
if (bytes == ARC_EVICT_ALL)
bytes_remaining = ARC_EVICT_ALL;
else if (total_evicted < bytes)
bytes_remaining = bytes - total_evicted;
else
break;
bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
markers[sublist_idx], spa, bytes_remaining);
scan_evicted += bytes_evicted;
total_evicted += bytes_evicted;
/* we've reached the end, wrap to the beginning */
if (++sublist_idx >= num_sublists)
sublist_idx = 0;
}
/*
* If we didn't evict anything during this scan, we have
* no reason to believe we'll evict more during another
* scan, so break the loop.
*/
if (scan_evicted == 0) {
/* This isn't possible, let's make that obvious */
ASSERT3S(bytes, !=, 0);
/*
* When bytes is ARC_EVICT_ALL, the only way to
* break the loop is when scan_evicted is zero.
* In that case, we actually have evicted enough,
* so we don't want to increment the kstat.
*/
if (bytes != ARC_EVICT_ALL) {
ASSERT3S(total_evicted, <, bytes);
ARCSTAT_BUMP(arcstat_evict_not_enough);
}
break;
}
}
for (int i = 0; i < num_sublists; i++) {
multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
multilist_sublist_remove(mls, markers[i]);
multilist_sublist_unlock(mls);
kmem_cache_free(hdr_full_cache, markers[i]);
}
kmem_free(markers, sizeof (*markers) * num_sublists);
return (total_evicted);
}
/*
* Flush all "evictable" data of the given type from the arc state
* specified. This will not evict any "active" buffers (i.e. referenced).
*
* When 'retry' is set to B_FALSE, the function will make a single pass
* over the state and evict any buffers that it can. Since it doesn't
* continually retry the eviction, it might end up leaving some buffers
* in the ARC due to lock misses.
*
* When 'retry' is set to B_TRUE, the function will continually retry the
* eviction until *all* evictable buffers have been removed from the
* state. As a result, if concurrent insertions into the state are
* allowed (e.g. if the ARC isn't shutting down), this function might
* wind up in an infinite loop, continually trying to evict buffers.
*/
static uint64_t
arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
boolean_t retry)
{
uint64_t evicted = 0;
while (refcount_count(&state->arcs_esize[type]) != 0) {
evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
if (!retry)
break;
}
return (evicted);
}
/*
* Evict the specified number of bytes from the state specified,
* restricting eviction to the spa and type given. This function
* prevents us from trying to evict more from a state's list than
* is "evictable", and to skip evicting altogether when passed a
* negative value for "bytes". In contrast, arc_evict_state() will
* evict everything it can, when passed a negative value for "bytes".
*/
static uint64_t
arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
arc_buf_contents_t type)
{
int64_t delta;
if (bytes > 0 && refcount_count(&state->arcs_esize[type]) > 0) {
delta = MIN(refcount_count(&state->arcs_esize[type]), bytes);
return (arc_evict_state(state, spa, delta, type));
}
return (0);
}
/*
* Evict metadata buffers from the cache, such that arc_meta_used is
* capped by the arc_meta_limit tunable.
*/
static uint64_t
arc_adjust_meta(void)
{
uint64_t total_evicted = 0;
int64_t target;
/*
* If we're over the meta limit, we want to evict enough
* metadata to get back under the meta limit. We don't want to
* evict so much that we drop the MRU below arc_p, though. If
* we're over the meta limit more than we're over arc_p, we
* evict some from the MRU here, and some from the MFU below.
*/
target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
(int64_t)(refcount_count(&arc_anon->arcs_size) +
refcount_count(&arc_mru->arcs_size) - arc_p));
total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
/*
* Similar to the above, we want to evict enough bytes to get us
* below the meta limit, but not so much as to drop us below the
* space allotted to the MFU (which is defined as arc_c - arc_p).
*/
target = MIN((int64_t)(arc_meta_used - arc_meta_limit),
(int64_t)(refcount_count(&arc_mfu->arcs_size) - (arc_c - arc_p)));
total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
return (total_evicted);
}
/*
* Return the type of the oldest buffer in the given arc state
*
* This function will select a random sublist of type ARC_BUFC_DATA and
* a random sublist of type ARC_BUFC_METADATA. The tail of each sublist
* is compared, and the type which contains the "older" buffer will be
* returned.
*/
static arc_buf_contents_t
arc_adjust_type(arc_state_t *state)
{
multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA];
multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA];
int data_idx = multilist_get_random_index(data_ml);
int meta_idx = multilist_get_random_index(meta_ml);
multilist_sublist_t *data_mls;
multilist_sublist_t *meta_mls;
arc_buf_contents_t type;
arc_buf_hdr_t *data_hdr;
arc_buf_hdr_t *meta_hdr;
/*
* We keep the sublist lock until we're finished, to prevent
* the headers from being destroyed via arc_evict_state().
*/
data_mls = multilist_sublist_lock(data_ml, data_idx);
meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
/*
* These two loops are to ensure we skip any markers that
* might be at the tail of the lists due to arc_evict_state().
*/
for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
if (data_hdr->b_spa != 0)
break;
}
for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
if (meta_hdr->b_spa != 0)
break;
}
if (data_hdr == NULL && meta_hdr == NULL) {
type = ARC_BUFC_DATA;
} else if (data_hdr == NULL) {
ASSERT3P(meta_hdr, !=, NULL);
type = ARC_BUFC_METADATA;
} else if (meta_hdr == NULL) {
ASSERT3P(data_hdr, !=, NULL);
type = ARC_BUFC_DATA;
} else {
ASSERT3P(data_hdr, !=, NULL);
ASSERT3P(meta_hdr, !=, NULL);
/* The headers can't be on the sublist without an L1 header */
ASSERT(HDR_HAS_L1HDR(data_hdr));
ASSERT(HDR_HAS_L1HDR(meta_hdr));
if (data_hdr->b_l1hdr.b_arc_access <
meta_hdr->b_l1hdr.b_arc_access) {
type = ARC_BUFC_DATA;
} else {
type = ARC_BUFC_METADATA;
}
}
multilist_sublist_unlock(meta_mls);
multilist_sublist_unlock(data_mls);
return (type);
}
/*
* Evict buffers from the cache, such that arc_size is capped by arc_c.
*/
static uint64_t
arc_adjust(void)
{
uint64_t total_evicted = 0;
uint64_t bytes;
int64_t target;
/*
* If we're over arc_meta_limit, we want to correct that before
* potentially evicting data buffers below.
*/
total_evicted += arc_adjust_meta();
/*
* Adjust MRU size
*
* If we're over the target cache size, we want to evict enough
* from the list to get back to our target size. We don't want
* to evict too much from the MRU, such that it drops below
* arc_p. So, if we're over our target cache size more than
* the MRU is over arc_p, we'll evict enough to get back to
* arc_p here, and then evict more from the MFU below.
*/
target = MIN((int64_t)(arc_size - arc_c),
(int64_t)(refcount_count(&arc_anon->arcs_size) +
refcount_count(&arc_mru->arcs_size) + arc_meta_used - arc_p));
/*
* If we're below arc_meta_min, always prefer to evict data.
* Otherwise, try to satisfy the requested number of bytes to
* evict from the type which contains older buffers; in an
* effort to keep newer buffers in the cache regardless of their
* type. If we cannot satisfy the number of bytes from this
* type, spill over into the next type.
*/
if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
arc_meta_used > arc_meta_min) {
bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
total_evicted += bytes;
/*
* If we couldn't evict our target number of bytes from
* metadata, we try to get the rest from data.
*/
target -= bytes;
total_evicted +=
arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
} else {
bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
total_evicted += bytes;
/*
* If we couldn't evict our target number of bytes from
* data, we try to get the rest from metadata.
*/
target -= bytes;
total_evicted +=
arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
}
/*
* Adjust MFU size
*
* Now that we've tried to evict enough from the MRU to get its
* size back to arc_p, if we're still above the target cache
* size, we evict the rest from the MFU.
*/
target = arc_size - arc_c;
if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
arc_meta_used > arc_meta_min) {
bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
total_evicted += bytes;
/*
* If we couldn't evict our target number of bytes from
* metadata, we try to get the rest from data.
*/
target -= bytes;
total_evicted +=
arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
} else {
bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
total_evicted += bytes;
/*
* If we couldn't evict our target number of bytes from
* data, we try to get the rest from data.
*/
target -= bytes;
total_evicted +=
arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
}
/*
* Adjust ghost lists
*
* In addition to the above, the ARC also defines target values
* for the ghost lists. The sum of the mru list and mru ghost
* list should never exceed the target size of the cache, and
* the sum of the mru list, mfu list, mru ghost list, and mfu
* ghost list should never exceed twice the target size of the
* cache. The following logic enforces these limits on the ghost
* caches, and evicts from them as needed.
*/
target = refcount_count(&arc_mru->arcs_size) +
refcount_count(&arc_mru_ghost->arcs_size) - arc_c;
bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA);
total_evicted += bytes;
target -= bytes;
total_evicted +=
arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
/*
* We assume the sum of the mru list and mfu list is less than
* or equal to arc_c (we enforced this above), which means we
* can use the simpler of the two equations below:
*
* mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
* mru ghost + mfu ghost <= arc_c
*/
target = refcount_count(&arc_mru_ghost->arcs_size) +
refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
total_evicted += bytes;
target -= bytes;
total_evicted +=
arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
return (total_evicted);
}
void
arc_flush(spa_t *spa, boolean_t retry)
{
uint64_t guid = 0;
/*
* If retry is B_TRUE, a spa must not be specified since we have
* no good way to determine if all of a spa's buffers have been
* evicted from an arc state.
*/
ASSERT(!retry || spa == 0);
if (spa != NULL)
guid = spa_load_guid(spa);
(void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
(void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
(void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
(void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
(void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
(void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
(void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
(void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
}
void
arc_shrink(int64_t to_free)
{
if (arc_c > arc_c_min) {
DTRACE_PROBE4(arc__shrink, uint64_t, arc_c, uint64_t,
arc_c_min, uint64_t, arc_p, uint64_t, to_free);
if (arc_c > arc_c_min + to_free)
atomic_add_64(&arc_c, -to_free);
else
arc_c = arc_c_min;
atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
if (arc_c > arc_size)
arc_c = MAX(arc_size, arc_c_min);
if (arc_p > arc_c)
arc_p = (arc_c >> 1);
DTRACE_PROBE2(arc__shrunk, uint64_t, arc_c, uint64_t,
arc_p);
ASSERT(arc_c >= arc_c_min);
ASSERT((int64_t)arc_p >= 0);
}
if (arc_size > arc_c) {
DTRACE_PROBE2(arc__shrink_adjust, uint64_t, arc_size,
uint64_t, arc_c);
(void) arc_adjust();
}
}
static long needfree = 0;
typedef enum free_memory_reason_t {
FMR_UNKNOWN,
FMR_NEEDFREE,
FMR_LOTSFREE,
FMR_SWAPFS_MINFREE,
FMR_PAGES_PP_MAXIMUM,
FMR_HEAP_ARENA,
FMR_ZIO_ARENA,
FMR_ZIO_FRAG,
} free_memory_reason_t;
int64_t last_free_memory;
free_memory_reason_t last_free_reason;
/*
* Additional reserve of pages for pp_reserve.
*/
int64_t arc_pages_pp_reserve = 64;
/*
* Additional reserve of pages for swapfs.
*/
int64_t arc_swapfs_reserve = 64;
/*
* Return the amount of memory that can be consumed before reclaim will be
* needed. Positive if there is sufficient free memory, negative indicates
* the amount of memory that needs to be freed up.
*/
static int64_t
arc_available_memory(void)
{
int64_t lowest = INT64_MAX;
int64_t n;
free_memory_reason_t r = FMR_UNKNOWN;
#ifdef _KERNEL
if (needfree > 0) {
n = PAGESIZE * (-needfree);
if (n < lowest) {
lowest = n;
r = FMR_NEEDFREE;
}
}
/*
* Cooperate with pagedaemon when it's time for it to scan
* and reclaim some pages.
*/
n = PAGESIZE * ((int64_t)freemem - zfs_arc_free_target);
if (n < lowest) {
lowest = n;
r = FMR_LOTSFREE;
}
#ifdef illumos
/*
* check that we're out of range of the pageout scanner. It starts to
* schedule paging if freemem is less than lotsfree and needfree.
* lotsfree is the high-water mark for pageout, and needfree is the
* number of needed free pages. We add extra pages here to make sure
* the scanner doesn't start up while we're freeing memory.
*/
n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
if (n < lowest) {
lowest = n;
r = FMR_LOTSFREE;
}
/*
* check to make sure that swapfs has enough space so that anon
* reservations can still succeed. anon_resvmem() checks that the
* availrmem is greater than swapfs_minfree, and the number of reserved
* swap pages. We also add a bit of extra here just to prevent
* circumstances from getting really dire.
*/
n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
desfree - arc_swapfs_reserve);
if (n < lowest) {
lowest = n;
r = FMR_SWAPFS_MINFREE;
}
/*
* Check that we have enough availrmem that memory locking (e.g., via
* mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
* stores the number of pages that cannot be locked; when availrmem
* drops below pages_pp_maximum, page locking mechanisms such as
* page_pp_lock() will fail.)
*/
n = PAGESIZE * (availrmem - pages_pp_maximum -
arc_pages_pp_reserve);
if (n < lowest) {
lowest = n;
r = FMR_PAGES_PP_MAXIMUM;
}
#endif /* illumos */
#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
/*
* If we're on an i386 platform, it's possible that we'll exhaust the
* kernel heap space before we ever run out of available physical
* memory. Most checks of the size of the heap_area compare against
* tune.t_minarmem, which is the minimum available real memory that we
* can have in the system. However, this is generally fixed at 25 pages
* which is so low that it's useless. In this comparison, we seek to
* calculate the total heap-size, and reclaim if more than 3/4ths of the
* heap is allocated. (Or, in the calculation, if less than 1/4th is
* free)
*/
n = (int64_t)vmem_size(heap_arena, VMEM_FREE) -
(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC) >> 2);
if (n < lowest) {
lowest = n;
r = FMR_HEAP_ARENA;
}
#define zio_arena NULL
#else
#define zio_arena heap_arena
#endif
/*
* If zio data pages are being allocated out of a separate heap segment,
* then enforce that the size of available vmem for this arena remains
* above about 1/16th free.
*
* Note: The 1/16th arena free requirement was put in place
* to aggressively evict memory from the arc in order to avoid
* memory fragmentation issues.
*/
if (zio_arena != NULL) {
n = (int64_t)vmem_size(zio_arena, VMEM_FREE) -
(vmem_size(zio_arena, VMEM_ALLOC) >> 4);
if (n < lowest) {
lowest = n;
r = FMR_ZIO_ARENA;
}
}
/*
* Above limits know nothing about real level of KVA fragmentation.
* Start aggressive reclamation if too little sequential KVA left.
*/
if (lowest > 0) {
n = (vmem_size(heap_arena, VMEM_MAXFREE) < SPA_MAXBLOCKSIZE) ?
-((int64_t)vmem_size(heap_arena, VMEM_ALLOC) >> 4) :
INT64_MAX;
if (n < lowest) {
lowest = n;
r = FMR_ZIO_FRAG;
}
}
#else /* _KERNEL */
/* Every 100 calls, free a small amount */
if (spa_get_random(100) == 0)
lowest = -1024;
#endif /* _KERNEL */
last_free_memory = lowest;
last_free_reason = r;
DTRACE_PROBE2(arc__available_memory, int64_t, lowest, int, r);
return (lowest);
}
/*
* Determine if the system is under memory pressure and is asking
* to reclaim memory. A return value of B_TRUE indicates that the system
* is under memory pressure and that the arc should adjust accordingly.
*/
static boolean_t
arc_reclaim_needed(void)
{
return (arc_available_memory() < 0);
}
extern kmem_cache_t *zio_buf_cache[];
extern kmem_cache_t *zio_data_buf_cache[];
extern kmem_cache_t *range_seg_cache;
static __noinline void
arc_kmem_reap_now(void)
{
size_t i;
kmem_cache_t *prev_cache = NULL;
kmem_cache_t *prev_data_cache = NULL;
DTRACE_PROBE(arc__kmem_reap_start);
#ifdef _KERNEL
if (arc_meta_used >= arc_meta_limit) {
/*
* We are exceeding our meta-data cache limit.
* Purge some DNLC entries to release holds on meta-data.
*/
dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
}
#if defined(__i386)
/*
* Reclaim unused memory from all kmem caches.
*/
kmem_reap();
#endif
#endif
for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
if (zio_buf_cache[i] != prev_cache) {
prev_cache = zio_buf_cache[i];
kmem_cache_reap_now(zio_buf_cache[i]);
}
if (zio_data_buf_cache[i] != prev_data_cache) {
prev_data_cache = zio_data_buf_cache[i];
kmem_cache_reap_now(zio_data_buf_cache[i]);
}
}
kmem_cache_reap_now(buf_cache);
kmem_cache_reap_now(hdr_full_cache);
kmem_cache_reap_now(hdr_l2only_cache);
kmem_cache_reap_now(range_seg_cache);
#ifdef illumos
if (zio_arena != NULL) {
/*
* Ask the vmem arena to reclaim unused memory from its
* quantum caches.
*/
vmem_qcache_reap(zio_arena);
}
#endif
DTRACE_PROBE(arc__kmem_reap_end);
}
/*
* Threads can block in arc_get_data_buf() waiting for this thread to evict
* enough data and signal them to proceed. When this happens, the threads in
* arc_get_data_buf() are sleeping while holding the hash lock for their
* particular arc header. Thus, we must be careful to never sleep on a
* hash lock in this thread. This is to prevent the following deadlock:
*
* - Thread A sleeps on CV in arc_get_data_buf() holding hash lock "L",
* waiting for the reclaim thread to signal it.
*
* - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter,
* fails, and goes to sleep forever.
*
* This possible deadlock is avoided by always acquiring a hash lock
* using mutex_tryenter() from arc_reclaim_thread().
*/
static void
arc_reclaim_thread(void *dummy __unused)
{
hrtime_t growtime = 0;
callb_cpr_t cpr;
CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG);
mutex_enter(&arc_reclaim_lock);
while (!arc_reclaim_thread_exit) {
uint64_t evicted = 0;
/*
* This is necessary in order for the mdb ::arc dcmd to
* show up to date information. Since the ::arc command
* does not call the kstat's update function, without
* this call, the command may show stale stats for the
* anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
* with this change, the data might be up to 1 second
* out of date; but that should suffice. The arc_state_t
* structures can be queried directly if more accurate
* information is needed.
*/
if (arc_ksp != NULL)
arc_ksp->ks_update(arc_ksp, KSTAT_READ);
mutex_exit(&arc_reclaim_lock);
/*
* We call arc_adjust() before (possibly) calling
* arc_kmem_reap_now(), so that we can wake up
* arc_get_data_buf() sooner.
*/
evicted = arc_adjust();
int64_t free_memory = arc_available_memory();
if (free_memory < 0) {
arc_no_grow = B_TRUE;
arc_warm = B_TRUE;
/*
* Wait at least zfs_grow_retry (default 60) seconds
* before considering growing.
*/
growtime = gethrtime() + SEC2NSEC(arc_grow_retry);
arc_kmem_reap_now();
/*
* If we are still low on memory, shrink the ARC
* so that we have arc_shrink_min free space.
*/
free_memory = arc_available_memory();
int64_t to_free =
(arc_c >> arc_shrink_shift) - free_memory;
if (to_free > 0) {
#ifdef _KERNEL
to_free = MAX(to_free, ptob(needfree));
#endif
arc_shrink(to_free);
}
} else if (free_memory < arc_c >> arc_no_grow_shift) {
arc_no_grow = B_TRUE;
} else if (gethrtime() >= growtime) {
arc_no_grow = B_FALSE;
}
mutex_enter(&arc_reclaim_lock);
/*
* If evicted is zero, we couldn't evict anything via
* arc_adjust(). This could be due to hash lock
* collisions, but more likely due to the majority of
* arc buffers being unevictable. Therefore, even if
* arc_size is above arc_c, another pass is unlikely to
* be helpful and could potentially cause us to enter an
* infinite loop.
*/
if (arc_size <= arc_c || evicted == 0) {
#ifdef _KERNEL
needfree = 0;
#endif
/*
* We're either no longer overflowing, or we
* can't evict anything more, so we should wake
* up any threads before we go to sleep.
*/
cv_broadcast(&arc_reclaim_waiters_cv);
/*
* Block until signaled, or after one second (we
* might need to perform arc_kmem_reap_now()
* even if we aren't being signalled)
*/
CALLB_CPR_SAFE_BEGIN(&cpr);
(void) cv_timedwait_hires(&arc_reclaim_thread_cv,
&arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0);
CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock);
}
}
arc_reclaim_thread_exit = B_FALSE;
cv_broadcast(&arc_reclaim_thread_cv);
CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */
thread_exit();
}
static u_int arc_dnlc_evicts_arg;
extern struct vfsops zfs_vfsops;
static void
arc_dnlc_evicts_thread(void *dummy __unused)
{
callb_cpr_t cpr;
u_int percent;
CALLB_CPR_INIT(&cpr, &arc_dnlc_evicts_lock, callb_generic_cpr, FTAG);
mutex_enter(&arc_dnlc_evicts_lock);
while (!arc_dnlc_evicts_thread_exit) {
CALLB_CPR_SAFE_BEGIN(&cpr);
(void) cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock);
CALLB_CPR_SAFE_END(&cpr, &arc_dnlc_evicts_lock);
if (arc_dnlc_evicts_arg != 0) {
percent = arc_dnlc_evicts_arg;
mutex_exit(&arc_dnlc_evicts_lock);
#ifdef _KERNEL
vnlru_free(desiredvnodes * percent / 100, &zfs_vfsops);
#endif
mutex_enter(&arc_dnlc_evicts_lock);
/*
* Clear our token only after vnlru_free()
* pass is done, to avoid false queueing of
* the requests.
*/
arc_dnlc_evicts_arg = 0;
}
}
arc_dnlc_evicts_thread_exit = FALSE;
cv_broadcast(&arc_dnlc_evicts_cv);
CALLB_CPR_EXIT(&cpr);
thread_exit();
}
void
dnlc_reduce_cache(void *arg)
{
u_int percent;
percent = (u_int)(uintptr_t)arg;
mutex_enter(&arc_dnlc_evicts_lock);
if (arc_dnlc_evicts_arg == 0) {
arc_dnlc_evicts_arg = percent;
cv_broadcast(&arc_dnlc_evicts_cv);
}
mutex_exit(&arc_dnlc_evicts_lock);
}
/*
* Adapt arc info given the number of bytes we are trying to add and
* the state that we are comming from. This function is only called
* when we are adding new content to the cache.
*/
static void
arc_adapt(int bytes, arc_state_t *state)
{
int mult;
uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
int64_t mrug_size = refcount_count(&arc_mru_ghost->arcs_size);
int64_t mfug_size = refcount_count(&arc_mfu_ghost->arcs_size);
if (state == arc_l2c_only)
return;
ASSERT(bytes > 0);
/*
* Adapt the target size of the MRU list:
* - if we just hit in the MRU ghost list, then increase
* the target size of the MRU list.
* - if we just hit in the MFU ghost list, then increase
* the target size of the MFU list by decreasing the
* target size of the MRU list.
*/
if (state == arc_mru_ghost) {
mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
} else if (state == arc_mfu_ghost) {
uint64_t delta;
mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
mult = MIN(mult, 10);
delta = MIN(bytes * mult, arc_p);
arc_p = MAX(arc_p_min, arc_p - delta);
}
ASSERT((int64_t)arc_p >= 0);
if (arc_reclaim_needed()) {
cv_signal(&arc_reclaim_thread_cv);
return;
}
if (arc_no_grow)
return;
if (arc_c >= arc_c_max)
return;
/*
* If we're within (2 * maxblocksize) bytes of the target
* cache size, increment the target cache size
*/
if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
DTRACE_PROBE1(arc__inc_adapt, int, bytes);
atomic_add_64(&arc_c, (int64_t)bytes);
if (arc_c > arc_c_max)
arc_c = arc_c_max;
else if (state == arc_anon)
atomic_add_64(&arc_p, (int64_t)bytes);
if (arc_p > arc_c)
arc_p = arc_c;
}
ASSERT((int64_t)arc_p >= 0);
}
/*
* Check if arc_size has grown past our upper threshold, determined by
* zfs_arc_overflow_shift.
*/
static boolean_t
arc_is_overflowing(void)
{
/* Always allow at least one block of overflow */
uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
arc_c >> zfs_arc_overflow_shift);
return (arc_size >= arc_c + overflow);
}
/*
* Allocate a block and return it to the caller. If we are hitting the
* hard limit for the cache size, we must sleep, waiting for the eviction
* thread to catch up. If we're past the target size but below the hard
* limit, we'll only signal the reclaim thread and continue on.
*/
static void *
arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
{
void *datap = NULL;
arc_state_t *state = hdr->b_l1hdr.b_state;
arc_buf_contents_t type = arc_buf_type(hdr);
arc_adapt(size, state);
/*
* If arc_size is currently overflowing, and has grown past our
* upper limit, we must be adding data faster than the evict
* thread can evict. Thus, to ensure we don't compound the
* problem by adding more data and forcing arc_size to grow even
* further past it's target size, we halt and wait for the
* eviction thread to catch up.
*
* It's also possible that the reclaim thread is unable to evict
* enough buffers to get arc_size below the overflow limit (e.g.
* due to buffers being un-evictable, or hash lock collisions).
* In this case, we want to proceed regardless if we're
* overflowing; thus we don't use a while loop here.
*/
if (arc_is_overflowing()) {
mutex_enter(&arc_reclaim_lock);
/*
* Now that we've acquired the lock, we may no longer be
* over the overflow limit, lets check.
*
* We're ignoring the case of spurious wake ups. If that
* were to happen, it'd let this thread consume an ARC
* buffer before it should have (i.e. before we're under
* the overflow limit and were signalled by the reclaim
* thread). As long as that is a rare occurrence, it
* shouldn't cause any harm.
*/
if (arc_is_overflowing()) {
cv_signal(&arc_reclaim_thread_cv);
cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
}
mutex_exit(&arc_reclaim_lock);
}
VERIFY3U(hdr->b_type, ==, type);
if (type == ARC_BUFC_METADATA) {
datap = zio_buf_alloc(size);
arc_space_consume(size, ARC_SPACE_META);
} else {
ASSERT(type == ARC_BUFC_DATA);
datap = zio_data_buf_alloc(size);
arc_space_consume(size, ARC_SPACE_DATA);
}
/*
* Update the state size. Note that ghost states have a
* "ghost size" and so don't need to be updated.
*/
if (!GHOST_STATE(state)) {
(void) refcount_add_many(&state->arcs_size, size, tag);
/*
* If this is reached via arc_read, the link is
* protected by the hash lock. If reached via
* arc_buf_alloc, the header should not be accessed by
* any other thread. And, if reached via arc_read_done,
* the hash lock will protect it if it's found in the
* hash table; otherwise no other thread should be
* trying to [add|remove]_reference it.
*/
if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
(void) refcount_add_many(&state->arcs_esize[type],
size, tag);
}
/*
* If we are growing the cache, and we are adding anonymous
* data, and we have outgrown arc_p, update arc_p
*/
if (arc_size < arc_c && hdr->b_l1hdr.b_state == arc_anon &&
(refcount_count(&arc_anon->arcs_size) +
refcount_count(&arc_mru->arcs_size) > arc_p))
arc_p = MIN(arc_c, arc_p + size);
}
ARCSTAT_BUMP(arcstat_allocated);
return (datap);
}
/*
* Free the arc data buffer.
*/
static void
arc_free_data_buf(arc_buf_hdr_t *hdr, void *data, uint64_t size, void *tag)
{
arc_state_t *state = hdr->b_l1hdr.b_state;
arc_buf_contents_t type = arc_buf_type(hdr);
/* protected by hash lock, if in the hash table */
if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
ASSERT(state != arc_anon && state != arc_l2c_only);
(void) refcount_remove_many(&state->arcs_esize[type],
size, tag);
}
(void) refcount_remove_many(&state->arcs_size, size, tag);
VERIFY3U(hdr->b_type, ==, type);
if (type == ARC_BUFC_METADATA) {
zio_buf_free(data, size);
arc_space_return(size, ARC_SPACE_META);
} else {
ASSERT(type == ARC_BUFC_DATA);
zio_data_buf_free(data, size);
arc_space_return(size, ARC_SPACE_DATA);
}
}
/*
* This routine is called whenever a buffer is accessed.
* NOTE: the hash lock is dropped in this function.
*/
static void
arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
{
clock_t now;
ASSERT(MUTEX_HELD(hash_lock));
ASSERT(HDR_HAS_L1HDR(hdr));
if (hdr->b_l1hdr.b_state == arc_anon) {
/*
* This buffer is not in the cache, and does not
* appear in our "ghost" list. Add the new buffer
* to the MRU state.
*/
ASSERT0(hdr->b_l1hdr.b_arc_access);
hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
arc_change_state(arc_mru, hdr, hash_lock);
} else if (hdr->b_l1hdr.b_state == arc_mru) {
now = ddi_get_lbolt();
/*
* If this buffer is here because of a prefetch, then either:
* - clear the flag if this is a "referencing" read
* (any subsequent access will bump this into the MFU state).
* or
* - move the buffer to the head of the list if this is
* another prefetch (to make it less likely to be evicted).
*/
if (HDR_PREFETCH(hdr)) {
if (refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
/* link protected by hash lock */
ASSERT(multilist_link_active(
&hdr->b_l1hdr.b_arc_node));
} else {
arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
ARCSTAT_BUMP(arcstat_mru_hits);
}
hdr->b_l1hdr.b_arc_access = now;
return;
}
/*
* This buffer has been "accessed" only once so far,
* but it is still in the cache. Move it to the MFU
* state.
*/
if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) {
/*
* More than 125ms have passed since we
* instantiated this buffer. Move it to the
* most frequently used state.
*/
hdr->b_l1hdr.b_arc_access = now;
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
arc_change_state(arc_mfu, hdr, hash_lock);
}
ARCSTAT_BUMP(arcstat_mru_hits);
} else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
arc_state_t *new_state;
/*
* This buffer has been "accessed" recently, but
* was evicted from the cache. Move it to the
* MFU state.
*/
if (HDR_PREFETCH(hdr)) {
new_state = arc_mru;
if (refcount_count(&hdr->b_l1hdr.b_refcnt) > 0)
arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
} else {
new_state = arc_mfu;
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
}
hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
arc_change_state(new_state, hdr, hash_lock);
ARCSTAT_BUMP(arcstat_mru_ghost_hits);
} else if (hdr->b_l1hdr.b_state == arc_mfu) {
/*
* This buffer has been accessed more than once and is
* still in the cache. Keep it in the MFU state.
*
* NOTE: an add_reference() that occurred when we did
* the arc_read() will have kicked this off the list.
* If it was a prefetch, we will explicitly move it to
* the head of the list now.
*/
if ((HDR_PREFETCH(hdr)) != 0) {
ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
/* link protected by hash_lock */
ASSERT(multilist_link_active(&hdr->b_l1hdr.b_arc_node));
}
ARCSTAT_BUMP(arcstat_mfu_hits);
hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
} else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
arc_state_t *new_state = arc_mfu;
/*
* This buffer has been accessed more than once but has
* been evicted from the cache. Move it back to the
* MFU state.
*/
if (HDR_PREFETCH(hdr)) {
/*
* This is a prefetch access...
* move this block back to the MRU state.
*/
ASSERT0(refcount_count(&hdr->b_l1hdr.b_refcnt));
new_state = arc_mru;
}
hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
arc_change_state(new_state, hdr, hash_lock);
ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
} else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
/*
* This buffer is on the 2nd Level ARC.
*/
hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
arc_change_state(arc_mfu, hdr, hash_lock);
} else {
ASSERT(!"invalid arc state");
}
}
/* a generic arc_done_func_t which you can use */
/* ARGSUSED */
void
arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
{
if (zio == NULL || zio->io_error == 0)
bcopy(buf->b_data, arg, arc_buf_size(buf));
arc_buf_destroy(buf, arg);
}
/* a generic arc_done_func_t */
void
arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
{
arc_buf_t **bufp = arg;
if (zio && zio->io_error) {
arc_buf_destroy(buf, arg);
*bufp = NULL;
} else {
*bufp = buf;
ASSERT(buf->b_data);
}
}
static void
arc_hdr_verify(arc_buf_hdr_t *hdr, blkptr_t *bp)
{
if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0);
ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
} else {
if (HDR_COMPRESSION_ENABLED(hdr)) {
ASSERT3U(HDR_GET_COMPRESS(hdr), ==,
BP_GET_COMPRESS(bp));
}
ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp));
}
}
static void
arc_read_done(zio_t *zio)
{
arc_buf_hdr_t *hdr = zio->io_private;
kmutex_t *hash_lock = NULL;
arc_callback_t *callback_list;
arc_callback_t *acb;
boolean_t freeable = B_FALSE;
boolean_t no_zio_error = (zio->io_error == 0);
/*
* The hdr was inserted into hash-table and removed from lists
* prior to starting I/O. We should find this header, since
* it's in the hash table, and it should be legit since it's
* not possible to evict it during the I/O. The only possible
* reason for it not to be found is if we were freed during the
* read.
*/
if (HDR_IN_HASH_TABLE(hdr)) {
ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
ASSERT3U(hdr->b_dva.dva_word[0], ==,
BP_IDENTITY(zio->io_bp)->dva_word[0]);
ASSERT3U(hdr->b_dva.dva_word[1], ==,
BP_IDENTITY(zio->io_bp)->dva_word[1]);
arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
&hash_lock);
ASSERT((found == hdr &&
DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
(found == hdr && HDR_L2_READING(hdr)));
ASSERT3P(hash_lock, !=, NULL);
}
if (no_zio_error) {
/* byteswap if necessary */
if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
if (BP_GET_LEVEL(zio->io_bp) > 0) {
hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
} else {
hdr->b_l1hdr.b_byteswap =
DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
}
} else {
hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
}
}
arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED);
if (l2arc_noprefetch && HDR_PREFETCH(hdr))
arc_hdr_clear_flags(hdr, ARC_FLAG_L2CACHE);
callback_list = hdr->b_l1hdr.b_acb;
ASSERT3P(callback_list, !=, NULL);
if (hash_lock && no_zio_error && hdr->b_l1hdr.b_state == arc_anon) {
/*
* Only call arc_access on anonymous buffers. This is because
* if we've issued an I/O for an evicted buffer, we've already
* called arc_access (to prevent any simultaneous readers from
* getting confused).
*/
arc_access(hdr, hash_lock);
}
/*
* If a read request has a callback (i.e. acb_done is not NULL), then we
* make a buf containing the data according to the parameters which were
* passed in. The implementation of arc_buf_alloc_impl() ensures that we
* aren't needlessly decompressing the data multiple times.
*/
int callback_cnt = 0;
for (acb = callback_list; acb != NULL; acb = acb->acb_next) {
if (!acb->acb_done)
continue;
/* This is a demand read since prefetches don't use callbacks */
callback_cnt++;
int error = arc_buf_alloc_impl(hdr, acb->acb_private,
acb->acb_compressed, no_zio_error, &acb->acb_buf);
if (no_zio_error) {
zio->io_error = error;
}
}
hdr->b_l1hdr.b_acb = NULL;
arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
if (callback_cnt == 0) {
ASSERT(HDR_PREFETCH(hdr));
ASSERT0(hdr->b_l1hdr.b_bufcnt);
ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL);
}
ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
callback_list != NULL);
if (no_zio_error) {
arc_hdr_verify(hdr, zio->io_bp);
} else {
arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
if (hdr->b_l1hdr.b_state != arc_anon)
arc_change_state(arc_anon, hdr, hash_lock);
if (HDR_IN_HASH_TABLE(hdr))
buf_hash_remove(hdr);
freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
}
/*
* Broadcast before we drop the hash_lock to avoid the possibility
* that the hdr (and hence the cv) might be freed before we get to
* the cv_broadcast().
*/
cv_broadcast(&hdr->b_l1hdr.b_cv);
if (hash_lock != NULL) {
mutex_exit(hash_lock);
} else {
/*
* This block was freed while we waited for the read to
* complete. It has been removed from the hash table and
* moved to the anonymous state (so that it won't show up
* in the cache).
*/
ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
freeable = refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
}
/* execute each callback and free its structure */
while ((acb = callback_list) != NULL) {
if (acb->acb_done)
acb->acb_done(zio, acb->acb_buf, acb->acb_private);
if (acb->acb_zio_dummy != NULL) {
acb->acb_zio_dummy->io_error = zio->io_error;
zio_nowait(acb->acb_zio_dummy);
}
callback_list = acb->acb_next;
kmem_free(acb, sizeof (arc_callback_t));
}
if (freeable)
arc_hdr_destroy(hdr);
}
/*
* "Read" the block at the specified DVA (in bp) via the
* cache. If the block is found in the cache, invoke the provided
* callback immediately and return. Note that the `zio' parameter
* in the callback will be NULL in this case, since no IO was
* required. If the block is not in the cache pass the read request
* on to the spa with a substitute callback function, so that the
* requested block will be added to the cache.
*
* If a read request arrives for a block that has a read in-progress,
* either wait for the in-progress read to complete (and return the
* results); or, if this is a read with a "done" func, add a record
* to the read to invoke the "done" func when the read completes,
* and return; or just return.
*
* arc_read_done() will invoke all the requested "done" functions
* for readers of this block.
*/
int
arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
void *private, zio_priority_t priority, int zio_flags,
arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
{
arc_buf_hdr_t *hdr = NULL;
kmutex_t *hash_lock = NULL;
zio_t *rzio;
uint64_t guid = spa_load_guid(spa);
boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW) != 0;
ASSERT(!BP_IS_EMBEDDED(bp) ||
BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
top:
if (!BP_IS_EMBEDDED(bp)) {
/*
* Embedded BP's have no DVA and require no I/O to "read".
* Create an anonymous arc buf to back it.
*/
hdr = buf_hash_find(guid, bp, &hash_lock);
}
if (hdr != NULL && HDR_HAS_L1HDR(hdr) && hdr->b_l1hdr.b_pdata != NULL) {
arc_buf_t *buf = NULL;
*arc_flags |= ARC_FLAG_CACHED;
if (HDR_IO_IN_PROGRESS(hdr)) {
if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
priority == ZIO_PRIORITY_SYNC_READ) {
/*
* This sync read must wait for an
* in-progress async read (e.g. a predictive
* prefetch). Async reads are queued
* separately at the vdev_queue layer, so
* this is a form of priority inversion.
* Ideally, we would "inherit" the demand
* i/o's priority by moving the i/o from
* the async queue to the synchronous queue,
* but there is currently no mechanism to do
* so. Track this so that we can evaluate
* the magnitude of this potential performance
* problem.
*
* Note that if the prefetch i/o is already
* active (has been issued to the device),
* the prefetch improved performance, because
* we issued it sooner than we would have
* without the prefetch.
*/
DTRACE_PROBE1(arc__sync__wait__for__async,
arc_buf_hdr_t *, hdr);
ARCSTAT_BUMP(arcstat_sync_wait_for_async);
}
if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
arc_hdr_clear_flags(hdr,
ARC_FLAG_PREDICTIVE_PREFETCH);
}
if (*arc_flags & ARC_FLAG_WAIT) {
cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
mutex_exit(hash_lock);
goto top;
}
ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
if (done) {
arc_callback_t *acb = NULL;
acb = kmem_zalloc(sizeof (arc_callback_t),
KM_SLEEP);
acb->acb_done = done;
acb->acb_private = private;
acb->acb_compressed = compressed_read;
if (pio != NULL)
acb->acb_zio_dummy = zio_null(pio,
spa, NULL, NULL, NULL, zio_flags);
ASSERT3P(acb->acb_done, !=, NULL);
acb->acb_next = hdr->b_l1hdr.b_acb;
hdr->b_l1hdr.b_acb = acb;
mutex_exit(hash_lock);
return (0);
}
mutex_exit(hash_lock);
return (0);
}
ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
hdr->b_l1hdr.b_state == arc_mfu);
if (done) {
if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
/*
* This is a demand read which does not have to
* wait for i/o because we did a predictive
* prefetch i/o for it, which has completed.
*/
DTRACE_PROBE1(
arc__demand__hit__predictive__prefetch,
arc_buf_hdr_t *, hdr);
ARCSTAT_BUMP(
arcstat_demand_hit_predictive_prefetch);
arc_hdr_clear_flags(hdr,
ARC_FLAG_PREDICTIVE_PREFETCH);
}
ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp));
/* Get a buf with the desired data in it. */
VERIFY0(arc_buf_alloc_impl(hdr, private,
compressed_read, B_TRUE, &buf));
} else if (*arc_flags & ARC_FLAG_PREFETCH &&
refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
}
DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
arc_access(hdr, hash_lock);
if (*arc_flags & ARC_FLAG_L2CACHE)
arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
mutex_exit(hash_lock);
ARCSTAT_BUMP(arcstat_hits);
ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
data, metadata, hits);
if (done)
done(NULL, buf, private);
} else {
uint64_t lsize = BP_GET_LSIZE(bp);
uint64_t psize = BP_GET_PSIZE(bp);
arc_callback_t *acb;
vdev_t *vd = NULL;
uint64_t addr = 0;
boolean_t devw = B_FALSE;
uint64_t size;
if (hdr == NULL) {
/* this block is not in the cache */
arc_buf_hdr_t *exists = NULL;
arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
BP_GET_COMPRESS(bp), type);
if (!BP_IS_EMBEDDED(bp)) {
hdr->b_dva = *BP_IDENTITY(bp);
hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
exists = buf_hash_insert(hdr, &hash_lock);
}
if (exists != NULL) {
/* somebody beat us to the hash insert */
mutex_exit(hash_lock);
buf_discard_identity(hdr);
arc_hdr_destroy(hdr);
goto top; /* restart the IO request */
}
} else {
/*
* This block is in the ghost cache. If it was L2-only
* (and thus didn't have an L1 hdr), we realloc the
* header to add an L1 hdr.
*/
if (!HDR_HAS_L1HDR(hdr)) {
hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
hdr_full_cache);
}
ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL);
ASSERT(GHOST_STATE(hdr->b_l1hdr.b_state));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
/*
* This is a delicate dance that we play here.
* This hdr is in the ghost list so we access it
* to move it out of the ghost list before we
* initiate the read. If it's a prefetch then
* it won't have a callback so we'll remove the
* reference that arc_buf_alloc_impl() created. We
* do this after we've called arc_access() to
* avoid hitting an assert in remove_reference().
*/
arc_access(hdr, hash_lock);
arc_hdr_alloc_pdata(hdr);
}
ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL);
size = arc_hdr_size(hdr);
/*
* If compression is enabled on the hdr, then will do
* RAW I/O and will store the compressed data in the hdr's
* data block. Otherwise, the hdr's data block will contain
* the uncompressed data.
*/
if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF) {
zio_flags |= ZIO_FLAG_RAW;
}
if (*arc_flags & ARC_FLAG_PREFETCH)
arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
if (*arc_flags & ARC_FLAG_L2CACHE)
arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
if (BP_GET_LEVEL(bp) > 0)
arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT);
if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH)
arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH);
ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
acb->acb_done = done;
acb->acb_private = private;
acb->acb_compressed = compressed_read;
ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
hdr->b_l1hdr.b_acb = acb;
arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
if (HDR_HAS_L2HDR(hdr) &&
(vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
devw = hdr->b_l2hdr.b_dev->l2ad_writing;
addr = hdr->b_l2hdr.b_daddr;
/*
* Lock out device removal.
*/
if (vdev_is_dead(vd) ||
!spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
vd = NULL;
}
if (priority == ZIO_PRIORITY_ASYNC_READ)
arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
else
arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
if (hash_lock != NULL)
mutex_exit(hash_lock);
/*
* At this point, we have a level 1 cache miss. Try again in
* L2ARC if possible.
*/
ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize);
DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
uint64_t, lsize, zbookmark_phys_t *, zb);
ARCSTAT_BUMP(arcstat_misses);
ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
data, metadata, misses);
#ifdef _KERNEL
#ifdef RACCT
if (racct_enable) {
PROC_LOCK(curproc);
racct_add_force(curproc, RACCT_READBPS, size);
racct_add_force(curproc, RACCT_READIOPS, 1);
PROC_UNLOCK(curproc);
}
#endif /* RACCT */
curthread->td_ru.ru_inblock++;
#endif
if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
/*
* Read from the L2ARC if the following are true:
* 1. The L2ARC vdev was previously cached.
* 2. This buffer still has L2ARC metadata.
* 3. This buffer isn't currently writing to the L2ARC.
* 4. The L2ARC entry wasn't evicted, which may
* also have invalidated the vdev.
* 5. This isn't prefetch and l2arc_noprefetch is set.
*/
if (HDR_HAS_L2HDR(hdr) &&
!HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
!(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
l2arc_read_callback_t *cb;
void* b_data;
DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
ARCSTAT_BUMP(arcstat_l2_hits);
cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
KM_SLEEP);
cb->l2rcb_hdr = hdr;
cb->l2rcb_bp = *bp;
cb->l2rcb_zb = *zb;
cb->l2rcb_flags = zio_flags;
uint64_t asize = vdev_psize_to_asize(vd, size);
if (asize != size) {
b_data = zio_data_buf_alloc(asize);
cb->l2rcb_data = b_data;
} else {
b_data = hdr->b_l1hdr.b_pdata;
}
ASSERT(addr >= VDEV_LABEL_START_SIZE &&
addr + asize < vd->vdev_psize -
VDEV_LABEL_END_SIZE);
/*
* l2arc read. The SCL_L2ARC lock will be
* released by l2arc_read_done().
* Issue a null zio if the underlying buffer
* was squashed to zero size by compression.
*/
ASSERT3U(HDR_GET_COMPRESS(hdr), !=,
ZIO_COMPRESS_EMPTY);
rzio = zio_read_phys(pio, vd, addr,
asize, b_data,
ZIO_CHECKSUM_OFF,
l2arc_read_done, cb, priority,
zio_flags | ZIO_FLAG_DONT_CACHE |
ZIO_FLAG_CANFAIL |
ZIO_FLAG_DONT_PROPAGATE |
ZIO_FLAG_DONT_RETRY, B_FALSE);
DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
zio_t *, rzio);
ARCSTAT_INCR(arcstat_l2_read_bytes, size);
if (*arc_flags & ARC_FLAG_NOWAIT) {
zio_nowait(rzio);
return (0);
}
ASSERT(*arc_flags & ARC_FLAG_WAIT);
if (zio_wait(rzio) == 0)
return (0);
/* l2arc read error; goto zio_read() */
} else {
DTRACE_PROBE1(l2arc__miss,
arc_buf_hdr_t *, hdr);
ARCSTAT_BUMP(arcstat_l2_misses);
if (HDR_L2_WRITING(hdr))
ARCSTAT_BUMP(arcstat_l2_rw_clash);
spa_config_exit(spa, SCL_L2ARC, vd);
}
} else {
if (vd != NULL)
spa_config_exit(spa, SCL_L2ARC, vd);
if (l2arc_ndev != 0) {
DTRACE_PROBE1(l2arc__miss,
arc_buf_hdr_t *, hdr);
ARCSTAT_BUMP(arcstat_l2_misses);
}
}
rzio = zio_read(pio, spa, bp, hdr->b_l1hdr.b_pdata, size,
arc_read_done, hdr, priority, zio_flags, zb);
if (*arc_flags & ARC_FLAG_WAIT)
return (zio_wait(rzio));
ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
zio_nowait(rzio);
}
return (0);
}
/*
* Notify the arc that a block was freed, and thus will never be used again.
*/
void
arc_freed(spa_t *spa, const blkptr_t *bp)
{
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
uint64_t guid = spa_load_guid(spa);
ASSERT(!BP_IS_EMBEDDED(bp));
hdr = buf_hash_find(guid, bp, &hash_lock);
if (hdr == NULL)
return;
/*
* We might be trying to free a block that is still doing I/O
* (i.e. prefetch) or has a reference (i.e. a dedup-ed,
* dmu_sync-ed block). If this block is being prefetched, then it
* would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr
* until the I/O completes. A block may also have a reference if it is
* part of a dedup-ed, dmu_synced write. The dmu_sync() function would
* have written the new block to its final resting place on disk but
* without the dedup flag set. This would have left the hdr in the MRU
* state and discoverable. When the txg finally syncs it detects that
* the block was overridden in open context and issues an override I/O.
* Since this is a dedup block, the override I/O will determine if the
* block is already in the DDT. If so, then it will replace the io_bp
* with the bp from the DDT and allow the I/O to finish. When the I/O
* reaches the done callback, dbuf_write_override_done, it will
* check to see if the io_bp and io_bp_override are identical.
* If they are not, then it indicates that the bp was replaced with
* the bp in the DDT and the override bp is freed. This allows
* us to arrive here with a reference on a block that is being
* freed. So if we have an I/O in progress, or a reference to
* this hdr, then we don't destroy the hdr.
*/
if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) &&
refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) {
arc_change_state(arc_anon, hdr, hash_lock);
arc_hdr_destroy(hdr);
mutex_exit(hash_lock);
} else {
mutex_exit(hash_lock);
}
}
/*
* Release this buffer from the cache, making it an anonymous buffer. This
* must be done after a read and prior to modifying the buffer contents.
* If the buffer has more than one reference, we must make
* a new hdr for the buffer.
*/
void
arc_release(arc_buf_t *buf, void *tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
/*
* It would be nice to assert that if it's DMU metadata (level >
* 0 || it's the dnode file), then it must be syncing context.
* But we don't know that information at this level.
*/
mutex_enter(&buf->b_evict_lock);
ASSERT(HDR_HAS_L1HDR(hdr));
/*
* We don't grab the hash lock prior to this check, because if
* the buffer's header is in the arc_anon state, it won't be
* linked into the hash table.
*/
if (hdr->b_l1hdr.b_state == arc_anon) {
mutex_exit(&buf->b_evict_lock);
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
ASSERT(!HDR_IN_HASH_TABLE(hdr));
ASSERT(!HDR_HAS_L2HDR(hdr));
ASSERT(HDR_EMPTY(hdr));
ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
hdr->b_l1hdr.b_arc_access = 0;
/*
* If the buf is being overridden then it may already
* have a hdr that is not empty.
*/
buf_discard_identity(hdr);
arc_buf_thaw(buf);
return;
}
kmutex_t *hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
/*
* This assignment is only valid as long as the hash_lock is
* held, we must be careful not to reference state or the
* b_state field after dropping the lock.
*/
arc_state_t *state = hdr->b_l1hdr.b_state;
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
ASSERT3P(state, !=, arc_anon);
/* this buffer is not on any list */
ASSERT3S(refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0);
if (HDR_HAS_L2HDR(hdr)) {
mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
/*
* We have to recheck this conditional again now that
* we're holding the l2ad_mtx to prevent a race with
* another thread which might be concurrently calling
* l2arc_evict(). In that case, l2arc_evict() might have
* destroyed the header's L2 portion as we were waiting
* to acquire the l2ad_mtx.
*/
if (HDR_HAS_L2HDR(hdr)) {
l2arc_trim(hdr);
arc_hdr_l2hdr_destroy(hdr);
}
mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
}
/*
* Do we have more than one buf?
*/
if (hdr->b_l1hdr.b_bufcnt > 1) {
arc_buf_hdr_t *nhdr;
uint64_t spa = hdr->b_spa;
uint64_t psize = HDR_GET_PSIZE(hdr);
uint64_t lsize = HDR_GET_LSIZE(hdr);
enum zio_compress compress = HDR_GET_COMPRESS(hdr);
arc_buf_contents_t type = arc_buf_type(hdr);
VERIFY3U(hdr->b_type, ==, type);
ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
(void) remove_reference(hdr, hash_lock, tag);
if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) {
ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
ASSERT(ARC_BUF_LAST(buf));
}
/*
* Pull the data off of this hdr and attach it to
* a new anonymous hdr. Also find the last buffer
* in the hdr's buffer list.
*/
arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
ASSERT3P(lastbuf, !=, NULL);
/*
* If the current arc_buf_t and the hdr are sharing their data
* buffer, then we must stop sharing that block.
*/
if (arc_buf_is_shared(buf)) {
VERIFY(!arc_buf_is_shared(lastbuf));
/*
* First, sever the block sharing relationship between
* buf and the arc_buf_hdr_t.
*/
arc_unshare_buf(hdr, buf);
/*
* Now we need to recreate the hdr's b_pdata. Since we
* have lastbuf handy, we try to share with it, but if
* we can't then we allocate a new b_pdata and copy the
* data from buf into it.
*/
if (arc_can_share(hdr, lastbuf)) {
arc_share_buf(hdr, lastbuf);
} else {
arc_hdr_alloc_pdata(hdr);
bcopy(buf->b_data, hdr->b_l1hdr.b_pdata, psize);
}
VERIFY3P(lastbuf->b_data, !=, NULL);
} else if (HDR_SHARED_DATA(hdr)) {
/*
* Uncompressed shared buffers are always at the end
* of the list. Compressed buffers don't have the
* same requirements. This makes it hard to
* simply assert that the lastbuf is shared so
* we rely on the hdr's compression flags to determine
* if we have a compressed, shared buffer.
*/
ASSERT(arc_buf_is_shared(lastbuf) ||
HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF);
ASSERT(!ARC_BUF_SHARED(buf));
}
ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL);
ASSERT3P(state, !=, arc_l2c_only);
(void) refcount_remove_many(&state->arcs_size,
arc_buf_size(buf), buf);
if (refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
ASSERT3P(state, !=, arc_l2c_only);
(void) refcount_remove_many(&state->arcs_esize[type],
arc_buf_size(buf), buf);
}
hdr->b_l1hdr.b_bufcnt -= 1;
arc_cksum_verify(buf);
#ifdef illumos
arc_buf_unwatch(buf);
#endif
mutex_exit(hash_lock);
/*
* Allocate a new hdr. The new hdr will contain a b_pdata
* buffer which will be freed in arc_write().
*/
nhdr = arc_hdr_alloc(spa, psize, lsize, compress, type);
ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL);
ASSERT0(nhdr->b_l1hdr.b_bufcnt);
ASSERT0(refcount_count(&nhdr->b_l1hdr.b_refcnt));
VERIFY3U(nhdr->b_type, ==, type);
ASSERT(!HDR_SHARED_DATA(nhdr));
nhdr->b_l1hdr.b_buf = buf;
nhdr->b_l1hdr.b_bufcnt = 1;
(void) refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
buf->b_hdr = nhdr;
mutex_exit(&buf->b_evict_lock);
(void) refcount_add_many(&arc_anon->arcs_size,
arc_buf_size(buf), buf);
} else {
mutex_exit(&buf->b_evict_lock);
ASSERT(refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
/* protected by hash lock, or hdr is on arc_anon */
ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
arc_change_state(arc_anon, hdr, hash_lock);
hdr->b_l1hdr.b_arc_access = 0;
mutex_exit(hash_lock);
buf_discard_identity(hdr);
arc_buf_thaw(buf);
}
}
int
arc_released(arc_buf_t *buf)
{
int released;
mutex_enter(&buf->b_evict_lock);
released = (buf->b_data != NULL &&
buf->b_hdr->b_l1hdr.b_state == arc_anon);
mutex_exit(&buf->b_evict_lock);
return (released);
}
#ifdef ZFS_DEBUG
int
arc_referenced(arc_buf_t *buf)
{
int referenced;
mutex_enter(&buf->b_evict_lock);
referenced = (refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
mutex_exit(&buf->b_evict_lock);
return (referenced);
}
#endif
static void
arc_write_ready(zio_t *zio)
{
arc_write_callback_t *callback = zio->io_private;
arc_buf_t *buf = callback->awcb_buf;
arc_buf_hdr_t *hdr = buf->b_hdr;
uint64_t psize = BP_IS_HOLE(zio->io_bp) ? 0 : BP_GET_PSIZE(zio->io_bp);
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT(!refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
/*
* If we're reexecuting this zio because the pool suspended, then
* cleanup any state that was previously set the first time the
* callback was invoked.
*/
if (zio->io_flags & ZIO_FLAG_REEXECUTED) {
arc_cksum_free(hdr);
#ifdef illumos
arc_buf_unwatch(buf);
#endif
if (hdr->b_l1hdr.b_pdata != NULL) {
if (arc_buf_is_shared(buf)) {
arc_unshare_buf(hdr, buf);
} else {
arc_hdr_free_pdata(hdr);
}
}
}
ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL);
ASSERT(!HDR_SHARED_DATA(hdr));
ASSERT(!arc_buf_is_shared(buf));
callback->awcb_ready(zio, buf, callback->awcb_private);
if (HDR_IO_IN_PROGRESS(hdr))
ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED);
arc_cksum_compute(buf);
arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
enum zio_compress compress;
if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
compress = ZIO_COMPRESS_OFF;
} else {
ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(zio->io_bp));
compress = BP_GET_COMPRESS(zio->io_bp);
}
HDR_SET_PSIZE(hdr, psize);
arc_hdr_set_compress(hdr, compress);
/*
* If the hdr is compressed, then copy the compressed
* zio contents into arc_buf_hdr_t. Otherwise, copy the original
* data buf into the hdr. Ideally, we would like to always copy the
* io_data into b_pdata but the user may have disabled compressed
* arc thus the on-disk block may or may not match what we maintain
* in the hdr's b_pdata field.
*/
if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
!ARC_BUF_COMPRESSED(buf)) {
ASSERT3U(BP_GET_COMPRESS(zio->io_bp), !=, ZIO_COMPRESS_OFF);
ASSERT3U(psize, >, 0);
arc_hdr_alloc_pdata(hdr);
bcopy(zio->io_data, hdr->b_l1hdr.b_pdata, psize);
} else {
ASSERT3P(buf->b_data, ==, zio->io_orig_data);
ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf));
ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
/*
* This hdr is not compressed so we're able to share
* the arc_buf_t data buffer with the hdr.
*/
arc_share_buf(hdr, buf);
ASSERT0(bcmp(zio->io_orig_data, hdr->b_l1hdr.b_pdata,
arc_buf_size(buf)));
}
arc_hdr_verify(hdr, zio->io_bp);
}
static void
arc_write_children_ready(zio_t *zio)
{
arc_write_callback_t *callback = zio->io_private;
arc_buf_t *buf = callback->awcb_buf;
callback->awcb_children_ready(zio, buf, callback->awcb_private);
}
/*
* The SPA calls this callback for each physical write that happens on behalf
* of a logical write. See the comment in dbuf_write_physdone() for details.
*/
static void
arc_write_physdone(zio_t *zio)
{
arc_write_callback_t *cb = zio->io_private;
if (cb->awcb_physdone != NULL)
cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
}
static void
arc_write_done(zio_t *zio)
{
arc_write_callback_t *callback = zio->io_private;
arc_buf_t *buf = callback->awcb_buf;
arc_buf_hdr_t *hdr = buf->b_hdr;
ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
if (zio->io_error == 0) {
arc_hdr_verify(hdr, zio->io_bp);
if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
buf_discard_identity(hdr);
} else {
hdr->b_dva = *BP_IDENTITY(zio->io_bp);
hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
}
} else {
ASSERT(HDR_EMPTY(hdr));
}
/*
* If the block to be written was all-zero or compressed enough to be
* embedded in the BP, no write was performed so there will be no
* dva/birth/checksum. The buffer must therefore remain anonymous
* (and uncached).
*/
if (!HDR_EMPTY(hdr)) {
arc_buf_hdr_t *exists;
kmutex_t *hash_lock;
ASSERT3U(zio->io_error, ==, 0);
arc_cksum_verify(buf);
exists = buf_hash_insert(hdr, &hash_lock);
if (exists != NULL) {
/*
* This can only happen if we overwrite for
* sync-to-convergence, because we remove
* buffers from the hash table when we arc_free().
*/
if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
panic("bad overwrite, hdr=%p exists=%p",
(void *)hdr, (void *)exists);
ASSERT(refcount_is_zero(
&exists->b_l1hdr.b_refcnt));
arc_change_state(arc_anon, exists, hash_lock);
mutex_exit(hash_lock);
arc_hdr_destroy(exists);
exists = buf_hash_insert(hdr, &hash_lock);
ASSERT3P(exists, ==, NULL);
} else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
/* nopwrite */
ASSERT(zio->io_prop.zp_nopwrite);
if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
panic("bad nopwrite, hdr=%p exists=%p",
(void *)hdr, (void *)exists);
} else {
/* Dedup */
ASSERT(hdr->b_l1hdr.b_bufcnt == 1);
ASSERT(hdr->b_l1hdr.b_state == arc_anon);
ASSERT(BP_GET_DEDUP(zio->io_bp));
ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
}
}
arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
/* if it's not anon, we are doing a scrub */
if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
arc_access(hdr, hash_lock);
mutex_exit(hash_lock);
} else {
arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
}
ASSERT(!refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
callback->awcb_done(zio, buf, callback->awcb_private);
kmem_free(callback, sizeof (arc_write_callback_t));
}
zio_t *
arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf,
boolean_t l2arc, const zio_prop_t *zp, arc_done_func_t *ready,
arc_done_func_t *children_ready, arc_done_func_t *physdone,
arc_done_func_t *done, void *private, zio_priority_t priority,
int zio_flags, const zbookmark_phys_t *zb)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
arc_write_callback_t *callback;
zio_t *zio;
ASSERT3P(ready, !=, NULL);
ASSERT3P(done, !=, NULL);
ASSERT(!HDR_IO_ERROR(hdr));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
if (l2arc)
arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
if (ARC_BUF_COMPRESSED(buf)) {
ASSERT3U(zp->zp_compress, !=, ZIO_COMPRESS_OFF);
ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf));
zio_flags |= ZIO_FLAG_RAW;
}
callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
callback->awcb_ready = ready;
callback->awcb_children_ready = children_ready;
callback->awcb_physdone = physdone;
callback->awcb_done = done;
callback->awcb_private = private;
callback->awcb_buf = buf;
/*
* The hdr's b_pdata is now stale, free it now. A new data block
* will be allocated when the zio pipeline calls arc_write_ready().
*/
if (hdr->b_l1hdr.b_pdata != NULL) {
/*
* If the buf is currently sharing the data block with
* the hdr then we need to break that relationship here.
* The hdr will remain with a NULL data pointer and the
* buf will take sole ownership of the block.
*/
if (arc_buf_is_shared(buf)) {
arc_unshare_buf(hdr, buf);
} else {
arc_hdr_free_pdata(hdr);
}
VERIFY3P(buf->b_data, !=, NULL);
arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF);
}
ASSERT(!arc_buf_is_shared(buf));
ASSERT3P(hdr->b_l1hdr.b_pdata, ==, NULL);
zio = zio_write(pio, spa, txg, bp, buf->b_data,
HDR_GET_LSIZE(hdr), arc_buf_size(buf), zp, arc_write_ready,
(children_ready != NULL) ? arc_write_children_ready : NULL,
arc_write_physdone, arc_write_done, callback,
priority, zio_flags, zb);
return (zio);
}
static int
arc_memory_throttle(uint64_t reserve, uint64_t txg)
{
#ifdef _KERNEL
uint64_t available_memory = ptob(freemem);
static uint64_t page_load = 0;
static uint64_t last_txg = 0;
#if defined(__i386) || !defined(UMA_MD_SMALL_ALLOC)
available_memory =
MIN(available_memory, ptob(vmem_size(heap_arena, VMEM_FREE)));
#endif
if (freemem > (uint64_t)physmem * arc_lotsfree_percent / 100)
return (0);
if (txg > last_txg) {
last_txg = txg;
page_load = 0;
}
/*
* If we are in pageout, we know that memory is already tight,
* the arc is already going to be evicting, so we just want to
* continue to let page writes occur as quickly as possible.
*/
if (curproc == pageproc) {
if (page_load > MAX(ptob(minfree), available_memory) / 4)
return (SET_ERROR(ERESTART));
/* Note: reserve is inflated, so we deflate */
page_load += reserve / 8;
return (0);
} else if (page_load > 0 && arc_reclaim_needed()) {
/* memory is low, delay before restarting */
ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
return (SET_ERROR(EAGAIN));
}
page_load = 0;
#endif
return (0);
}
void
arc_tempreserve_clear(uint64_t reserve)
{
atomic_add_64(&arc_tempreserve, -reserve);
ASSERT((int64_t)arc_tempreserve >= 0);
}
int
arc_tempreserve_space(uint64_t reserve, uint64_t txg)
{
int error;
uint64_t anon_size;
if (reserve > arc_c/4 && !arc_no_grow) {
arc_c = MIN(arc_c_max, reserve * 4);
DTRACE_PROBE1(arc__set_reserve, uint64_t, arc_c);
}
if (reserve > arc_c)
return (SET_ERROR(ENOMEM));
/*
* Don't count loaned bufs as in flight dirty data to prevent long
* network delays from blocking transactions that are ready to be
* assigned to a txg.
*/
/* assert that it has not wrapped around */
ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
anon_size = MAX((int64_t)(refcount_count(&arc_anon->arcs_size) -
arc_loaned_bytes), 0);
/*
* Writes will, almost always, require additional memory allocations
* in order to compress/encrypt/etc the data. We therefore need to
* make sure that there is sufficient available memory for this.
*/
error = arc_memory_throttle(reserve, txg);
if (error != 0)
return (error);
/*
* Throttle writes when the amount of dirty data in the cache
* gets too large. We try to keep the cache less than half full
* of dirty blocks so that our sync times don't grow too large.
* Note: if two requests come in concurrently, we might let them
* both succeed, when one of them should fail. Not a huge deal.
*/
if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
anon_size > arc_c / 4) {
uint64_t meta_esize =
refcount_count(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
uint64_t data_esize =
refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
"anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
arc_tempreserve >> 10, meta_esize >> 10,
data_esize >> 10, reserve >> 10, arc_c >> 10);
return (SET_ERROR(ERESTART));
}
atomic_add_64(&arc_tempreserve, reserve);
return (0);
}
static void
arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
kstat_named_t *evict_data, kstat_named_t *evict_metadata)
{
size->value.ui64 = refcount_count(&state->arcs_size);
evict_data->value.ui64 =
refcount_count(&state->arcs_esize[ARC_BUFC_DATA]);
evict_metadata->value.ui64 =
refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]);
}
static int
arc_kstat_update(kstat_t *ksp, int rw)
{
arc_stats_t *as = ksp->ks_data;
if (rw == KSTAT_WRITE) {
return (EACCES);
} else {
arc_kstat_update_state(arc_anon,
&as->arcstat_anon_size,
&as->arcstat_anon_evictable_data,
&as->arcstat_anon_evictable_metadata);
arc_kstat_update_state(arc_mru,
&as->arcstat_mru_size,
&as->arcstat_mru_evictable_data,
&as->arcstat_mru_evictable_metadata);
arc_kstat_update_state(arc_mru_ghost,
&as->arcstat_mru_ghost_size,
&as->arcstat_mru_ghost_evictable_data,
&as->arcstat_mru_ghost_evictable_metadata);
arc_kstat_update_state(arc_mfu,
&as->arcstat_mfu_size,
&as->arcstat_mfu_evictable_data,
&as->arcstat_mfu_evictable_metadata);
arc_kstat_update_state(arc_mfu_ghost,
&as->arcstat_mfu_ghost_size,
&as->arcstat_mfu_ghost_evictable_data,
&as->arcstat_mfu_ghost_evictable_metadata);
}
return (0);
}
/*
* This function *must* return indices evenly distributed between all
* sublists of the multilist. This is needed due to how the ARC eviction
* code is laid out; arc_evict_state() assumes ARC buffers are evenly
* distributed between all sublists and uses this assumption when
* deciding which sublist to evict from and how much to evict from it.
*/
unsigned int
arc_state_multilist_index_func(multilist_t *ml, void *obj)
{
arc_buf_hdr_t *hdr = obj;
/*
* We rely on b_dva to generate evenly distributed index
* numbers using buf_hash below. So, as an added precaution,
* let's make sure we never add empty buffers to the arc lists.
*/
ASSERT(!HDR_EMPTY(hdr));
/*
* The assumption here, is the hash value for a given
* arc_buf_hdr_t will remain constant throughout it's lifetime
* (i.e. it's b_spa, b_dva, and b_birth fields don't change).
* Thus, we don't need to store the header's sublist index
* on insertion, as this index can be recalculated on removal.
*
* Also, the low order bits of the hash value are thought to be
* distributed evenly. Otherwise, in the case that the multilist
* has a power of two number of sublists, each sublists' usage
* would not be evenly distributed.
*/
return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
multilist_get_num_sublists(ml));
}
#ifdef _KERNEL
static eventhandler_tag arc_event_lowmem = NULL;
static void
arc_lowmem(void *arg __unused, int howto __unused)
{
mutex_enter(&arc_reclaim_lock);
/* XXX: Memory deficit should be passed as argument. */
needfree = btoc(arc_c >> arc_shrink_shift);
DTRACE_PROBE(arc__needfree);
cv_signal(&arc_reclaim_thread_cv);
/*
* It is unsafe to block here in arbitrary threads, because we can come
* here from ARC itself and may hold ARC locks and thus risk a deadlock
* with ARC reclaim thread.
*/
if (curproc == pageproc)
(void) cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
mutex_exit(&arc_reclaim_lock);
}
#endif
static void
arc_state_init(void)
{
arc_anon = &ARC_anon;
arc_mru = &ARC_mru;
arc_mru_ghost = &ARC_mru_ghost;
arc_mfu = &ARC_mfu;
arc_mfu_ghost = &ARC_mfu_ghost;
arc_l2c_only = &ARC_l2c_only;
arc_mru->arcs_list[ARC_BUFC_METADATA] =
multilist_create(sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
arc_state_multilist_index_func);
arc_mru->arcs_list[ARC_BUFC_DATA] =
multilist_create(sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
arc_state_multilist_index_func);
arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] =
multilist_create(sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
arc_state_multilist_index_func);
arc_mru_ghost->arcs_list[ARC_BUFC_DATA] =
multilist_create(sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
arc_state_multilist_index_func);
arc_mfu->arcs_list[ARC_BUFC_METADATA] =
multilist_create(sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
arc_state_multilist_index_func);
arc_mfu->arcs_list[ARC_BUFC_DATA] =
multilist_create(sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
arc_state_multilist_index_func);
arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] =
multilist_create(sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
arc_state_multilist_index_func);
arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] =
multilist_create(sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
arc_state_multilist_index_func);
arc_l2c_only->arcs_list[ARC_BUFC_METADATA] =
multilist_create(sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
arc_state_multilist_index_func);
arc_l2c_only->arcs_list[ARC_BUFC_DATA] =
multilist_create(sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
arc_state_multilist_index_func);
refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
refcount_create(&arc_anon->arcs_size);
refcount_create(&arc_mru->arcs_size);
refcount_create(&arc_mru_ghost->arcs_size);
refcount_create(&arc_mfu->arcs_size);
refcount_create(&arc_mfu_ghost->arcs_size);
refcount_create(&arc_l2c_only->arcs_size);
}
static void
arc_state_fini(void)
{
refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
refcount_destroy(&arc_anon->arcs_size);
refcount_destroy(&arc_mru->arcs_size);
refcount_destroy(&arc_mru_ghost->arcs_size);
refcount_destroy(&arc_mfu->arcs_size);
refcount_destroy(&arc_mfu_ghost->arcs_size);
refcount_destroy(&arc_l2c_only->arcs_size);
multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]);
multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]);
multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]);
multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]);
multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
}
uint64_t
arc_max_bytes(void)
{
return (arc_c_max);
}
void
arc_init(void)
{
int i, prefetch_tunable_set = 0;
/*
* allmem is "all memory that we could possibly use".
*/
#ifdef illumos
#ifdef _KERNEL
uint64_t allmem = ptob(physmem - swapfs_minfree);
#else
uint64_t allmem = (physmem * PAGESIZE) / 2;
#endif
#else
uint64_t allmem = kmem_size();
#endif
mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL);
cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL);
mutex_init(&arc_dnlc_evicts_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&arc_dnlc_evicts_cv, NULL, CV_DEFAULT, NULL);
/* Convert seconds to clock ticks */
arc_min_prefetch_lifespan = 1 * hz;
/* set min cache to 1/32 of all memory, or arc_abs_min, whichever is more */
arc_c_min = MAX(allmem / 32, arc_abs_min);
/* set max to 5/8 of all memory, or all but 1GB, whichever is more */
if (allmem >= 1 << 30)
arc_c_max = allmem - (1 << 30);
else
arc_c_max = arc_c_min;
arc_c_max = MAX(allmem * 5 / 8, arc_c_max);
/*
* In userland, there's only the memory pressure that we artificially
* create (see arc_available_memory()). Don't let arc_c get too
* small, because it can cause transactions to be larger than
* arc_c, causing arc_tempreserve_space() to fail.
*/
#ifndef _KERNEL
arc_c_min = arc_c_max / 2;
#endif
#ifdef _KERNEL
/*
* Allow the tunables to override our calculations if they are
* reasonable.
*/
if (zfs_arc_max > arc_abs_min && zfs_arc_max < allmem) {
arc_c_max = zfs_arc_max;
arc_c_min = MIN(arc_c_min, arc_c_max);
}
if (zfs_arc_min > arc_abs_min && zfs_arc_min <= arc_c_max)
arc_c_min = zfs_arc_min;
#endif
arc_c = arc_c_max;
arc_p = (arc_c >> 1);
arc_size = 0;
/* limit meta-data to 1/4 of the arc capacity */
arc_meta_limit = arc_c_max / 4;
#ifdef _KERNEL
/*
* Metadata is stored in the kernel's heap. Don't let us
* use more than half the heap for the ARC.
*/
arc_meta_limit = MIN(arc_meta_limit,
vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2);
#endif
/* Allow the tunable to override if it is reasonable */
if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
arc_meta_limit = zfs_arc_meta_limit;
if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
arc_c_min = arc_meta_limit / 2;
if (zfs_arc_meta_min > 0) {
arc_meta_min = zfs_arc_meta_min;
} else {
arc_meta_min = arc_c_min / 2;
}
if (zfs_arc_grow_retry > 0)
arc_grow_retry = zfs_arc_grow_retry;
if (zfs_arc_shrink_shift > 0)
arc_shrink_shift = zfs_arc_shrink_shift;
/*
* Ensure that arc_no_grow_shift is less than arc_shrink_shift.
*/
if (arc_no_grow_shift >= arc_shrink_shift)
arc_no_grow_shift = arc_shrink_shift - 1;
if (zfs_arc_p_min_shift > 0)
arc_p_min_shift = zfs_arc_p_min_shift;
/* if kmem_flags are set, lets try to use less memory */
if (kmem_debugging())
arc_c = arc_c / 2;
if (arc_c < arc_c_min)
arc_c = arc_c_min;
zfs_arc_min = arc_c_min;
zfs_arc_max = arc_c_max;
arc_state_init();
buf_init();
arc_reclaim_thread_exit = B_FALSE;
arc_dnlc_evicts_thread_exit = FALSE;
arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
if (arc_ksp != NULL) {
arc_ksp->ks_data = &arc_stats;
arc_ksp->ks_update = arc_kstat_update;
kstat_install(arc_ksp);
}
(void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
TS_RUN, minclsyspri);
#ifdef _KERNEL
arc_event_lowmem = EVENTHANDLER_REGISTER(vm_lowmem, arc_lowmem, NULL,
EVENTHANDLER_PRI_FIRST);
#endif
(void) thread_create(NULL, 0, arc_dnlc_evicts_thread, NULL, 0, &p0,
TS_RUN, minclsyspri);
arc_dead = B_FALSE;
arc_warm = B_FALSE;
/*
* Calculate maximum amount of dirty data per pool.
*
* If it has been set by /etc/system, take that.
* Otherwise, use a percentage of physical memory defined by
* zfs_dirty_data_max_percent (default 10%) with a cap at
* zfs_dirty_data_max_max (default 4GB).
*/
if (zfs_dirty_data_max == 0) {
zfs_dirty_data_max = ptob(physmem) *
zfs_dirty_data_max_percent / 100;
zfs_dirty_data_max = MIN(zfs_dirty_data_max,
zfs_dirty_data_max_max);
}
#ifdef _KERNEL
if (TUNABLE_INT_FETCH("vfs.zfs.prefetch_disable", &zfs_prefetch_disable))
prefetch_tunable_set = 1;
#ifdef __i386__
if (prefetch_tunable_set == 0) {
printf("ZFS NOTICE: Prefetch is disabled by default on i386 "
"-- to enable,\n");
printf(" add \"vfs.zfs.prefetch_disable=0\" "
"to /boot/loader.conf.\n");
zfs_prefetch_disable = 1;
}
#else
if ((((uint64_t)physmem * PAGESIZE) < (1ULL << 32)) &&
prefetch_tunable_set == 0) {
printf("ZFS NOTICE: Prefetch is disabled by default if less "
"than 4GB of RAM is present;\n"
" to enable, add \"vfs.zfs.prefetch_disable=0\" "
"to /boot/loader.conf.\n");
zfs_prefetch_disable = 1;
}
#endif
/* Warn about ZFS memory and address space requirements. */
if (((uint64_t)physmem * PAGESIZE) < (256 + 128 + 64) * (1 << 20)) {
printf("ZFS WARNING: Recommended minimum RAM size is 512MB; "
"expect unstable behavior.\n");
}
if (allmem < 512 * (1 << 20)) {
printf("ZFS WARNING: Recommended minimum kmem_size is 512MB; "
"expect unstable behavior.\n");
printf(" Consider tuning vm.kmem_size and "
"vm.kmem_size_max\n");
printf(" in /boot/loader.conf.\n");
}
#endif
}
void
arc_fini(void)
{
mutex_enter(&arc_reclaim_lock);
arc_reclaim_thread_exit = B_TRUE;
/*
* The reclaim thread will set arc_reclaim_thread_exit back to
* B_FALSE when it is finished exiting; we're waiting for that.
*/
while (arc_reclaim_thread_exit) {
cv_signal(&arc_reclaim_thread_cv);
cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock);
}
mutex_exit(&arc_reclaim_lock);
/* Use B_TRUE to ensure *all* buffers are evicted */
arc_flush(NULL, B_TRUE);
mutex_enter(&arc_dnlc_evicts_lock);
arc_dnlc_evicts_thread_exit = TRUE;
/*
* The user evicts thread will set arc_user_evicts_thread_exit
* to FALSE when it is finished exiting; we're waiting for that.
*/
while (arc_dnlc_evicts_thread_exit) {
cv_signal(&arc_dnlc_evicts_cv);
cv_wait(&arc_dnlc_evicts_cv, &arc_dnlc_evicts_lock);
}
mutex_exit(&arc_dnlc_evicts_lock);
arc_dead = B_TRUE;
if (arc_ksp != NULL) {
kstat_delete(arc_ksp);
arc_ksp = NULL;
}
mutex_destroy(&arc_reclaim_lock);
cv_destroy(&arc_reclaim_thread_cv);
cv_destroy(&arc_reclaim_waiters_cv);
mutex_destroy(&arc_dnlc_evicts_lock);
cv_destroy(&arc_dnlc_evicts_cv);
arc_state_fini();
buf_fini();
ASSERT0(arc_loaned_bytes);
#ifdef _KERNEL
if (arc_event_lowmem != NULL)
EVENTHANDLER_DEREGISTER(vm_lowmem, arc_event_lowmem);
#endif
}
/*
* Level 2 ARC
*
* The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
* It uses dedicated storage devices to hold cached data, which are populated
* using large infrequent writes. The main role of this cache is to boost
* the performance of random read workloads. The intended L2ARC devices
* include short-stroked disks, solid state disks, and other media with
* substantially faster read latency than disk.
*
* +-----------------------+
* | ARC |
* +-----------------------+
* | ^ ^
* | | |
* l2arc_feed_thread() arc_read()
* | | |
* | l2arc read |
* V | |
* +---------------+ |
* | L2ARC | |
* +---------------+ |
* | ^ |
* l2arc_write() | |
* | | |
* V | |
* +-------+ +-------+
* | vdev | | vdev |
* | cache | | cache |
* +-------+ +-------+
* +=========+ .-----.
* : L2ARC : |-_____-|
* : devices : | Disks |
* +=========+ `-_____-'
*
* Read requests are satisfied from the following sources, in order:
*
* 1) ARC
* 2) vdev cache of L2ARC devices
* 3) L2ARC devices
* 4) vdev cache of disks
* 5) disks
*
* Some L2ARC device types exhibit extremely slow write performance.
* To accommodate for this there are some significant differences between
* the L2ARC and traditional cache design:
*
* 1. There is no eviction path from the ARC to the L2ARC. Evictions from
* the ARC behave as usual, freeing buffers and placing headers on ghost
* lists. The ARC does not send buffers to the L2ARC during eviction as
* this would add inflated write latencies for all ARC memory pressure.
*
* 2. The L2ARC attempts to cache data from the ARC before it is evicted.
* It does this by periodically scanning buffers from the eviction-end of
* the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
* not already there. It scans until a headroom of buffers is satisfied,
* which itself is a buffer for ARC eviction. If a compressible buffer is
* found during scanning and selected for writing to an L2ARC device, we
* temporarily boost scanning headroom during the next scan cycle to make
* sure we adapt to compression effects (which might significantly reduce
* the data volume we write to L2ARC). The thread that does this is
* l2arc_feed_thread(), illustrated below; example sizes are included to
* provide a better sense of ratio than this diagram:
*
* head --> tail
* +---------------------+----------+
* ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
* +---------------------+----------+ | o L2ARC eligible
* ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
* +---------------------+----------+ |
* 15.9 Gbytes ^ 32 Mbytes |
* headroom |
* l2arc_feed_thread()
* |
* l2arc write hand <--[oooo]--'
* | 8 Mbyte
* | write max
* V
* +==============================+
* L2ARC dev |####|#|###|###| |####| ... |
* +==============================+
* 32 Gbytes
*
* 3. If an ARC buffer is copied to the L2ARC but then hit instead of
* evicted, then the L2ARC has cached a buffer much sooner than it probably
* needed to, potentially wasting L2ARC device bandwidth and storage. It is
* safe to say that this is an uncommon case, since buffers at the end of
* the ARC lists have moved there due to inactivity.
*
* 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
* then the L2ARC simply misses copying some buffers. This serves as a
* pressure valve to prevent heavy read workloads from both stalling the ARC
* with waits and clogging the L2ARC with writes. This also helps prevent
* the potential for the L2ARC to churn if it attempts to cache content too
* quickly, such as during backups of the entire pool.
*
* 5. After system boot and before the ARC has filled main memory, there are
* no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
* lists can remain mostly static. Instead of searching from tail of these
* lists as pictured, the l2arc_feed_thread() will search from the list heads
* for eligible buffers, greatly increasing its chance of finding them.
*
* The L2ARC device write speed is also boosted during this time so that
* the L2ARC warms up faster. Since there have been no ARC evictions yet,
* there are no L2ARC reads, and no fear of degrading read performance
* through increased writes.
*
* 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
* the vdev queue can aggregate them into larger and fewer writes. Each
* device is written to in a rotor fashion, sweeping writes through
* available space then repeating.
*
* 7. The L2ARC does not store dirty content. It never needs to flush
* write buffers back to disk based storage.
*
* 8. If an ARC buffer is written (and dirtied) which also exists in the
* L2ARC, the now stale L2ARC buffer is immediately dropped.
*
* The performance of the L2ARC can be tweaked by a number of tunables, which
* may be necessary for different workloads:
*
* l2arc_write_max max write bytes per interval
* l2arc_write_boost extra write bytes during device warmup
* l2arc_noprefetch skip caching prefetched buffers
* l2arc_headroom number of max device writes to precache
* l2arc_headroom_boost when we find compressed buffers during ARC
* scanning, we multiply headroom by this
* percentage factor for the next scan cycle,
* since more compressed buffers are likely to
* be present
* l2arc_feed_secs seconds between L2ARC writing
*
* Tunables may be removed or added as future performance improvements are
* integrated, and also may become zpool properties.
*
* There are three key functions that control how the L2ARC warms up:
*
* l2arc_write_eligible() check if a buffer is eligible to cache
* l2arc_write_size() calculate how much to write
* l2arc_write_interval() calculate sleep delay between writes
*
* These three functions determine what to write, how much, and how quickly
* to send writes.
*/
static boolean_t
l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
{
/*
* A buffer is *not* eligible for the L2ARC if it:
* 1. belongs to a different spa.
* 2. is already cached on the L2ARC.
* 3. has an I/O in progress (it may be an incomplete read).
* 4. is flagged not eligible (zfs property).
*/
if (hdr->b_spa != spa_guid) {
ARCSTAT_BUMP(arcstat_l2_write_spa_mismatch);
return (B_FALSE);
}
if (HDR_HAS_L2HDR(hdr)) {
ARCSTAT_BUMP(arcstat_l2_write_in_l2);
return (B_FALSE);
}
if (HDR_IO_IN_PROGRESS(hdr)) {
ARCSTAT_BUMP(arcstat_l2_write_hdr_io_in_progress);
return (B_FALSE);
}
if (!HDR_L2CACHE(hdr)) {
ARCSTAT_BUMP(arcstat_l2_write_not_cacheable);
return (B_FALSE);
}
return (B_TRUE);
}
static uint64_t
l2arc_write_size(void)
{
uint64_t size;
/*
* Make sure our globals have meaningful values in case the user
* altered them.
*/
size = l2arc_write_max;
if (size == 0) {
cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
"be greater than zero, resetting it to the default (%d)",
L2ARC_WRITE_SIZE);
size = l2arc_write_max = L2ARC_WRITE_SIZE;
}
if (arc_warm == B_FALSE)
size += l2arc_write_boost;
return (size);
}
static clock_t
l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
{
clock_t interval, next, now;
/*
* If the ARC lists are busy, increase our write rate; if the
* lists are stale, idle back. This is achieved by checking
* how much we previously wrote - if it was more than half of
* what we wanted, schedule the next write much sooner.
*/
if (l2arc_feed_again && wrote > (wanted / 2))
interval = (hz * l2arc_feed_min_ms) / 1000;
else
interval = hz * l2arc_feed_secs;
now = ddi_get_lbolt();
next = MAX(now, MIN(now + interval, began + interval));
return (next);
}
/*
* Cycle through L2ARC devices. This is how L2ARC load balances.
* If a device is returned, this also returns holding the spa config lock.
*/
static l2arc_dev_t *
l2arc_dev_get_next(void)
{
l2arc_dev_t *first, *next = NULL;
/*
* Lock out the removal of spas (spa_namespace_lock), then removal
* of cache devices (l2arc_dev_mtx). Once a device has been selected,
* both locks will be dropped and a spa config lock held instead.
*/
mutex_enter(&spa_namespace_lock);
mutex_enter(&l2arc_dev_mtx);
/* if there are no vdevs, there is nothing to do */
if (l2arc_ndev == 0)
goto out;
first = NULL;
next = l2arc_dev_last;
do {
/* loop around the list looking for a non-faulted vdev */
if (next == NULL) {
next = list_head(l2arc_dev_list);
} else {
next = list_next(l2arc_dev_list, next);
if (next == NULL)
next = list_head(l2arc_dev_list);
}
/* if we have come back to the start, bail out */
if (first == NULL)
first = next;
else if (next == first)
break;
} while (vdev_is_dead(next->l2ad_vdev));
/* if we were unable to find any usable vdevs, return NULL */
if (vdev_is_dead(next->l2ad_vdev))
next = NULL;
l2arc_dev_last = next;
out:
mutex_exit(&l2arc_dev_mtx);
/*
* Grab the config lock to prevent the 'next' device from being
* removed while we are writing to it.
*/
if (next != NULL)
spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
mutex_exit(&spa_namespace_lock);
return (next);
}
/*
* Free buffers that were tagged for destruction.
*/
static void
l2arc_do_free_on_write()
{
list_t *buflist;
l2arc_data_free_t *df, *df_prev;
mutex_enter(&l2arc_free_on_write_mtx);
buflist = l2arc_free_on_write;
for (df = list_tail(buflist); df; df = df_prev) {
df_prev = list_prev(buflist, df);
ASSERT3P(df->l2df_data, !=, NULL);
if (df->l2df_type == ARC_BUFC_METADATA) {
zio_buf_free(df->l2df_data, df->l2df_size);
} else {
ASSERT(df->l2df_type == ARC_BUFC_DATA);
zio_data_buf_free(df->l2df_data, df->l2df_size);
}
list_remove(buflist, df);
kmem_free(df, sizeof (l2arc_data_free_t));
}
mutex_exit(&l2arc_free_on_write_mtx);
}
/*
* A write to a cache device has completed. Update all headers to allow
* reads from these buffers to begin.
*/
static void
l2arc_write_done(zio_t *zio)
{
l2arc_write_callback_t *cb;
l2arc_dev_t *dev;
list_t *buflist;
arc_buf_hdr_t *head, *hdr, *hdr_prev;
kmutex_t *hash_lock;
int64_t bytes_dropped = 0;
cb = zio->io_private;
ASSERT3P(cb, !=, NULL);
dev = cb->l2wcb_dev;
ASSERT3P(dev, !=, NULL);
head = cb->l2wcb_head;
ASSERT3P(head, !=, NULL);
buflist = &dev->l2ad_buflist;
ASSERT3P(buflist, !=, NULL);
DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
l2arc_write_callback_t *, cb);
if (zio->io_error != 0)
ARCSTAT_BUMP(arcstat_l2_writes_error);
/*
* All writes completed, or an error was hit.
*/
top:
mutex_enter(&dev->l2ad_mtx);
for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
hdr_prev = list_prev(buflist, hdr);
hash_lock = HDR_LOCK(hdr);
/*
* We cannot use mutex_enter or else we can deadlock
* with l2arc_write_buffers (due to swapping the order
* the hash lock and l2ad_mtx are taken).
*/
if (!mutex_tryenter(hash_lock)) {
/*
* Missed the hash lock. We must retry so we
* don't leave the ARC_FLAG_L2_WRITING bit set.
*/
ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
/*
* We don't want to rescan the headers we've
* already marked as having been written out, so
* we reinsert the head node so we can pick up
* where we left off.
*/
list_remove(buflist, head);
list_insert_after(buflist, hdr, head);
mutex_exit(&dev->l2ad_mtx);
/*
* We wait for the hash lock to become available
* to try and prevent busy waiting, and increase
* the chance we'll be able to acquire the lock
* the next time around.
*/
mutex_enter(hash_lock);
mutex_exit(hash_lock);
goto top;
}
/*
* We could not have been moved into the arc_l2c_only
* state while in-flight due to our ARC_FLAG_L2_WRITING
* bit being set. Let's just ensure that's being enforced.
*/
ASSERT(HDR_HAS_L1HDR(hdr));
if (zio->io_error != 0) {
/*
* Error - drop L2ARC entry.
*/
list_remove(buflist, hdr);
l2arc_trim(hdr);
arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
ARCSTAT_INCR(arcstat_l2_asize, -arc_hdr_size(hdr));
ARCSTAT_INCR(arcstat_l2_size, -HDR_GET_LSIZE(hdr));
bytes_dropped += arc_hdr_size(hdr);
(void) refcount_remove_many(&dev->l2ad_alloc,
arc_hdr_size(hdr), hdr);
}
/*
* Allow ARC to begin reads and ghost list evictions to
* this L2ARC entry.
*/
arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING);
mutex_exit(hash_lock);
}
atomic_inc_64(&l2arc_writes_done);
list_remove(buflist, head);
ASSERT(!HDR_HAS_L1HDR(head));
kmem_cache_free(hdr_l2only_cache, head);
mutex_exit(&dev->l2ad_mtx);
vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
l2arc_do_free_on_write();
kmem_free(cb, sizeof (l2arc_write_callback_t));
}
/*
* A read to a cache device completed. Validate buffer contents before
* handing over to the regular ARC routines.
*/
static void
l2arc_read_done(zio_t *zio)
{
l2arc_read_callback_t *cb;
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
boolean_t valid_cksum;
ASSERT3P(zio->io_vd, !=, NULL);
ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
cb = zio->io_private;
ASSERT3P(cb, !=, NULL);
hdr = cb->l2rcb_hdr;
ASSERT3P(hdr, !=, NULL);
hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
/*
* If the data was read into a temporary buffer,
* move it and free the buffer.
*/
if (cb->l2rcb_data != NULL) {
ASSERT3U(arc_hdr_size(hdr), <, zio->io_size);
if (zio->io_error == 0) {
bcopy(cb->l2rcb_data, hdr->b_l1hdr.b_pdata,
arc_hdr_size(hdr));
}
/*
* The following must be done regardless of whether
* there was an error:
* - free the temporary buffer
* - point zio to the real ARC buffer
* - set zio size accordingly
* These are required because zio is either re-used for
* an I/O of the block in the case of the error
* or the zio is passed to arc_read_done() and it
* needs real data.
*/
zio_data_buf_free(cb->l2rcb_data, zio->io_size);
zio->io_size = zio->io_orig_size = arc_hdr_size(hdr);
zio->io_data = zio->io_orig_data = hdr->b_l1hdr.b_pdata;
}
ASSERT3P(zio->io_data, !=, NULL);
/*
* Check this survived the L2ARC journey.
*/
ASSERT3P(zio->io_data, ==, hdr->b_l1hdr.b_pdata);
zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
valid_cksum = arc_cksum_is_equal(hdr, zio);
if (valid_cksum && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
mutex_exit(hash_lock);
zio->io_private = hdr;
arc_read_done(zio);
} else {
mutex_exit(hash_lock);
/*
* Buffer didn't survive caching. Increment stats and
* reissue to the original storage device.
*/
if (zio->io_error != 0) {
ARCSTAT_BUMP(arcstat_l2_io_error);
} else {
zio->io_error = SET_ERROR(EIO);
}
if (!valid_cksum)
ARCSTAT_BUMP(arcstat_l2_cksum_bad);
/*
* If there's no waiter, issue an async i/o to the primary
* storage now. If there *is* a waiter, the caller must
* issue the i/o in a context where it's OK to block.
*/
if (zio->io_waiter == NULL) {
zio_t *pio = zio_unique_parent(zio);
ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
zio_nowait(zio_read(pio, zio->io_spa, zio->io_bp,
hdr->b_l1hdr.b_pdata, zio->io_size, arc_read_done,
hdr, zio->io_priority, cb->l2rcb_flags,
&cb->l2rcb_zb));
}
}
kmem_free(cb, sizeof (l2arc_read_callback_t));
}
/*
* This is the list priority from which the L2ARC will search for pages to
* cache. This is used within loops (0..3) to cycle through lists in the
* desired order. This order can have a significant effect on cache
* performance.
*
* Currently the metadata lists are hit first, MFU then MRU, followed by
* the data lists. This function returns a locked list, and also returns
* the lock pointer.
*/
static multilist_sublist_t *
l2arc_sublist_lock(int list_num)
{
multilist_t *ml = NULL;
unsigned int idx;
ASSERT(list_num >= 0 && list_num <= 3);
switch (list_num) {
case 0:
ml = arc_mfu->arcs_list[ARC_BUFC_METADATA];
break;
case 1:
ml = arc_mru->arcs_list[ARC_BUFC_METADATA];
break;
case 2:
ml = arc_mfu->arcs_list[ARC_BUFC_DATA];
break;
case 3:
ml = arc_mru->arcs_list[ARC_BUFC_DATA];
break;
}
/*
* Return a randomly-selected sublist. This is acceptable
* because the caller feeds only a little bit of data for each
* call (8MB). Subsequent calls will result in different
* sublists being selected.
*/
idx = multilist_get_random_index(ml);
return (multilist_sublist_lock(ml, idx));
}
/*
* Evict buffers from the device write hand to the distance specified in
* bytes. This distance may span populated buffers, it may span nothing.
* This is clearing a region on the L2ARC device ready for writing.
* If the 'all' boolean is set, every buffer is evicted.
*/
static void
l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
{
list_t *buflist;
arc_buf_hdr_t *hdr, *hdr_prev;
kmutex_t *hash_lock;
uint64_t taddr;
buflist = &dev->l2ad_buflist;
if (!all && dev->l2ad_first) {
/*
* This is the first sweep through the device. There is
* nothing to evict.
*/
return;
}
if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
/*
* When nearing the end of the device, evict to the end
* before the device write hand jumps to the start.
*/
taddr = dev->l2ad_end;
} else {
taddr = dev->l2ad_hand + distance;
}
DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
uint64_t, taddr, boolean_t, all);
top:
mutex_enter(&dev->l2ad_mtx);
for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
hdr_prev = list_prev(buflist, hdr);
hash_lock = HDR_LOCK(hdr);
/*
* We cannot use mutex_enter or else we can deadlock
* with l2arc_write_buffers (due to swapping the order
* the hash lock and l2ad_mtx are taken).
*/
if (!mutex_tryenter(hash_lock)) {
/*
* Missed the hash lock. Retry.
*/
ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
mutex_exit(&dev->l2ad_mtx);
mutex_enter(hash_lock);
mutex_exit(hash_lock);
goto top;
}
if (HDR_L2_WRITE_HEAD(hdr)) {
/*
* We hit a write head node. Leave it for
* l2arc_write_done().
*/
list_remove(buflist, hdr);
mutex_exit(hash_lock);
continue;
}
if (!all && HDR_HAS_L2HDR(hdr) &&
(hdr->b_l2hdr.b_daddr >= taddr ||
hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
/*
* We've evicted to the target address,
* or the end of the device.
*/
mutex_exit(hash_lock);
break;
}
ASSERT(HDR_HAS_L2HDR(hdr));
if (!HDR_HAS_L1HDR(hdr)) {
ASSERT(!HDR_L2_READING(hdr));
/*
* This doesn't exist in the ARC. Destroy.
* arc_hdr_destroy() will call list_remove()
* and decrement arcstat_l2_size.
*/
arc_change_state(arc_anon, hdr, hash_lock);
arc_hdr_destroy(hdr);
} else {
ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
/*
* Invalidate issued or about to be issued
* reads, since we may be about to write
* over this location.
*/
if (HDR_L2_READING(hdr)) {
ARCSTAT_BUMP(arcstat_l2_evict_reading);
arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED);
}
/* Ensure this header has finished being written */
ASSERT(!HDR_L2_WRITING(hdr));
arc_hdr_l2hdr_destroy(hdr);
}
mutex_exit(hash_lock);
}
mutex_exit(&dev->l2ad_mtx);
}
/*
* Find and write ARC buffers to the L2ARC device.
*
* An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
* for reading until they have completed writing.
* The headroom_boost is an in-out parameter used to maintain headroom boost
* state between calls to this function.
*
* Returns the number of bytes actually written (which may be smaller than
* the delta by which the device hand has changed due to alignment).
*/
static uint64_t
l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
{
arc_buf_hdr_t *hdr, *hdr_prev, *head;
uint64_t write_asize, write_psize, write_sz, headroom;
boolean_t full;
l2arc_write_callback_t *cb;
zio_t *pio, *wzio;
uint64_t guid = spa_load_guid(spa);
int try;
ASSERT3P(dev->l2ad_vdev, !=, NULL);
pio = NULL;
write_sz = write_asize = write_psize = 0;
full = B_FALSE;
head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR);
ARCSTAT_BUMP(arcstat_l2_write_buffer_iter);
/*
* Copy buffers for L2ARC writing.
*/
for (try = 0; try <= 3; try++) {
multilist_sublist_t *mls = l2arc_sublist_lock(try);
uint64_t passed_sz = 0;
ARCSTAT_BUMP(arcstat_l2_write_buffer_list_iter);
/*
* L2ARC fast warmup.
*
* Until the ARC is warm and starts to evict, read from the
* head of the ARC lists rather than the tail.
*/
if (arc_warm == B_FALSE)
hdr = multilist_sublist_head(mls);
else
hdr = multilist_sublist_tail(mls);
if (hdr == NULL)
ARCSTAT_BUMP(arcstat_l2_write_buffer_list_null_iter);
headroom = target_sz * l2arc_headroom;
if (zfs_compressed_arc_enabled)
headroom = (headroom * l2arc_headroom_boost) / 100;
for (; hdr; hdr = hdr_prev) {
kmutex_t *hash_lock;
if (arc_warm == B_FALSE)
hdr_prev = multilist_sublist_next(mls, hdr);
else
hdr_prev = multilist_sublist_prev(mls, hdr);
ARCSTAT_INCR(arcstat_l2_write_buffer_bytes_scanned,
HDR_GET_LSIZE(hdr));
hash_lock = HDR_LOCK(hdr);
if (!mutex_tryenter(hash_lock)) {
ARCSTAT_BUMP(arcstat_l2_write_trylock_fail);
/*
* Skip this buffer rather than waiting.
*/
continue;
}
passed_sz += HDR_GET_LSIZE(hdr);
if (passed_sz > headroom) {
/*
* Searched too far.
*/
mutex_exit(hash_lock);
ARCSTAT_BUMP(arcstat_l2_write_passed_headroom);
break;
}
if (!l2arc_write_eligible(guid, hdr)) {
mutex_exit(hash_lock);
continue;
}
/*
* We rely on the L1 portion of the header below, so
* it's invalid for this header to have been evicted out
* of the ghost cache, prior to being written out. The
* ARC_FLAG_L2_WRITING bit ensures this won't happen.
*/
ASSERT(HDR_HAS_L1HDR(hdr));
ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
ASSERT3P(hdr->b_l1hdr.b_pdata, !=, NULL);
ASSERT3U(arc_hdr_size(hdr), >, 0);
uint64_t size = arc_hdr_size(hdr);
uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev,
size);
if ((write_psize + asize) > target_sz) {
full = B_TRUE;
mutex_exit(hash_lock);
ARCSTAT_BUMP(arcstat_l2_write_full);
break;
}
if (pio == NULL) {
/*
* Insert a dummy header on the buflist so
* l2arc_write_done() can find where the
* write buffers begin without searching.
*/
mutex_enter(&dev->l2ad_mtx);
list_insert_head(&dev->l2ad_buflist, head);
mutex_exit(&dev->l2ad_mtx);
cb = kmem_alloc(
sizeof (l2arc_write_callback_t), KM_SLEEP);
cb->l2wcb_dev = dev;
cb->l2wcb_head = head;
pio = zio_root(spa, l2arc_write_done, cb,
ZIO_FLAG_CANFAIL);
ARCSTAT_BUMP(arcstat_l2_write_pios);
}
hdr->b_l2hdr.b_dev = dev;
hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
arc_hdr_set_flags(hdr,
ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR);
mutex_enter(&dev->l2ad_mtx);
list_insert_head(&dev->l2ad_buflist, hdr);
mutex_exit(&dev->l2ad_mtx);
(void) refcount_add_many(&dev->l2ad_alloc, size, hdr);
/*
* Normally the L2ARC can use the hdr's data, but if
* we're sharing data between the hdr and one of its
* bufs, L2ARC needs its own copy of the data so that
* the ZIO below can't race with the buf consumer. To
* ensure that this copy will be available for the
* lifetime of the ZIO and be cleaned up afterwards, we
* add it to the l2arc_free_on_write queue.
*/
void *to_write;
if (!HDR_SHARED_DATA(hdr) && size == asize) {
to_write = hdr->b_l1hdr.b_pdata;
} else {
arc_buf_contents_t type = arc_buf_type(hdr);
if (type == ARC_BUFC_METADATA) {
to_write = zio_buf_alloc(asize);
} else {
ASSERT3U(type, ==, ARC_BUFC_DATA);
to_write = zio_data_buf_alloc(asize);
}
bcopy(hdr->b_l1hdr.b_pdata, to_write, size);
if (asize != size)
bzero(to_write + size, asize - size);
l2arc_free_data_on_write(to_write, asize, type);
}
wzio = zio_write_phys(pio, dev->l2ad_vdev,
hdr->b_l2hdr.b_daddr, asize, to_write,
ZIO_CHECKSUM_OFF, NULL, hdr,
ZIO_PRIORITY_ASYNC_WRITE,
ZIO_FLAG_CANFAIL, B_FALSE);
write_sz += HDR_GET_LSIZE(hdr);
DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
zio_t *, wzio);
write_asize += size;
write_psize += asize;
dev->l2ad_hand += asize;
mutex_exit(hash_lock);
(void) zio_nowait(wzio);
}
multilist_sublist_unlock(mls);
if (full == B_TRUE)
break;
}
/* No buffers selected for writing? */
if (pio == NULL) {
ASSERT0(write_sz);
ASSERT(!HDR_HAS_L1HDR(head));
kmem_cache_free(hdr_l2only_cache, head);
return (0);
}
ASSERT3U(write_psize, <=, target_sz);
ARCSTAT_BUMP(arcstat_l2_writes_sent);
ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize);
ARCSTAT_INCR(arcstat_l2_size, write_sz);
ARCSTAT_INCR(arcstat_l2_asize, write_asize);
vdev_space_update(dev->l2ad_vdev, write_asize, 0, 0);
/*
* Bump device hand to the device start if it is approaching the end.
* l2arc_evict() will already have evicted ahead for this case.
*/
if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
dev->l2ad_hand = dev->l2ad_start;
dev->l2ad_first = B_FALSE;
}
dev->l2ad_writing = B_TRUE;
(void) zio_wait(pio);
dev->l2ad_writing = B_FALSE;
return (write_asize);
}
/*
* This thread feeds the L2ARC at regular intervals. This is the beating
* heart of the L2ARC.
*/
static void
l2arc_feed_thread(void *dummy __unused)
{
callb_cpr_t cpr;
l2arc_dev_t *dev;
spa_t *spa;
uint64_t size, wrote;
clock_t begin, next = ddi_get_lbolt();
CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
mutex_enter(&l2arc_feed_thr_lock);
while (l2arc_thread_exit == 0) {
CALLB_CPR_SAFE_BEGIN(&cpr);
(void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
next - ddi_get_lbolt());
CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
next = ddi_get_lbolt() + hz;
/*
* Quick check for L2ARC devices.
*/
mutex_enter(&l2arc_dev_mtx);
if (l2arc_ndev == 0) {
mutex_exit(&l2arc_dev_mtx);
continue;
}
mutex_exit(&l2arc_dev_mtx);
begin = ddi_get_lbolt();
/*
* This selects the next l2arc device to write to, and in
* doing so the next spa to feed from: dev->l2ad_spa. This
* will return NULL if there are now no l2arc devices or if
* they are all faulted.
*
* If a device is returned, its spa's config lock is also
* held to prevent device removal. l2arc_dev_get_next()
* will grab and release l2arc_dev_mtx.
*/
if ((dev = l2arc_dev_get_next()) == NULL)
continue;
spa = dev->l2ad_spa;
ASSERT3P(spa, !=, NULL);
/*
* If the pool is read-only then force the feed thread to
* sleep a little longer.
*/
if (!spa_writeable(spa)) {
next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
spa_config_exit(spa, SCL_L2ARC, dev);
continue;
}
/*
* Avoid contributing to memory pressure.
*/
if (arc_reclaim_needed()) {
ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
spa_config_exit(spa, SCL_L2ARC, dev);
continue;
}
ARCSTAT_BUMP(arcstat_l2_feeds);
size = l2arc_write_size();
/*
* Evict L2ARC buffers that will be overwritten.
*/
l2arc_evict(dev, size, B_FALSE);
/*
* Write ARC buffers.
*/
wrote = l2arc_write_buffers(spa, dev, size);
/*
* Calculate interval between writes.
*/
next = l2arc_write_interval(begin, size, wrote);
spa_config_exit(spa, SCL_L2ARC, dev);
}
l2arc_thread_exit = 0;
cv_broadcast(&l2arc_feed_thr_cv);
CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
thread_exit();
}
boolean_t
l2arc_vdev_present(vdev_t *vd)
{
l2arc_dev_t *dev;
mutex_enter(&l2arc_dev_mtx);
for (dev = list_head(l2arc_dev_list); dev != NULL;
dev = list_next(l2arc_dev_list, dev)) {
if (dev->l2ad_vdev == vd)
break;
}
mutex_exit(&l2arc_dev_mtx);
return (dev != NULL);
}
/*
* Add a vdev for use by the L2ARC. By this point the spa has already
* validated the vdev and opened it.
*/
void
l2arc_add_vdev(spa_t *spa, vdev_t *vd)
{
l2arc_dev_t *adddev;
ASSERT(!l2arc_vdev_present(vd));
vdev_ashift_optimize(vd);
/*
* Create a new l2arc device entry.
*/
adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
adddev->l2ad_spa = spa;
adddev->l2ad_vdev = vd;
adddev->l2ad_start = VDEV_LABEL_START_SIZE;
adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
adddev->l2ad_hand = adddev->l2ad_start;
adddev->l2ad_first = B_TRUE;
adddev->l2ad_writing = B_FALSE;
mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
/*
* This is a list of all ARC buffers that are still valid on the
* device.
*/
list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
refcount_create(&adddev->l2ad_alloc);
/*
* Add device to global list
*/
mutex_enter(&l2arc_dev_mtx);
list_insert_head(l2arc_dev_list, adddev);
atomic_inc_64(&l2arc_ndev);
mutex_exit(&l2arc_dev_mtx);
}
/*
* Remove a vdev from the L2ARC.
*/
void
l2arc_remove_vdev(vdev_t *vd)
{
l2arc_dev_t *dev, *nextdev, *remdev = NULL;
/*
* Find the device by vdev
*/
mutex_enter(&l2arc_dev_mtx);
for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
nextdev = list_next(l2arc_dev_list, dev);
if (vd == dev->l2ad_vdev) {
remdev = dev;
break;
}
}
ASSERT3P(remdev, !=, NULL);
/*
* Remove device from global list
*/
list_remove(l2arc_dev_list, remdev);
l2arc_dev_last = NULL; /* may have been invalidated */
atomic_dec_64(&l2arc_ndev);
mutex_exit(&l2arc_dev_mtx);
/*
* Clear all buflists and ARC references. L2ARC device flush.
*/
l2arc_evict(remdev, 0, B_TRUE);
list_destroy(&remdev->l2ad_buflist);
mutex_destroy(&remdev->l2ad_mtx);
refcount_destroy(&remdev->l2ad_alloc);
kmem_free(remdev, sizeof (l2arc_dev_t));
}
void
l2arc_init(void)
{
l2arc_thread_exit = 0;
l2arc_ndev = 0;
l2arc_writes_sent = 0;
l2arc_writes_done = 0;
mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
l2arc_dev_list = &L2ARC_dev_list;
l2arc_free_on_write = &L2ARC_free_on_write;
list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
offsetof(l2arc_dev_t, l2ad_node));
list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
offsetof(l2arc_data_free_t, l2df_list_node));
}
void
l2arc_fini(void)
{
/*
* This is called from dmu_fini(), which is called from spa_fini();
* Because of this, we can assume that all l2arc devices have
* already been removed when the pools themselves were removed.
*/
l2arc_do_free_on_write();
mutex_destroy(&l2arc_feed_thr_lock);
cv_destroy(&l2arc_feed_thr_cv);
mutex_destroy(&l2arc_dev_mtx);
mutex_destroy(&l2arc_free_on_write_mtx);
list_destroy(l2arc_dev_list);
list_destroy(l2arc_free_on_write);
}
void
l2arc_start(void)
{
if (!(spa_mode_global & FWRITE))
return;
(void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
TS_RUN, minclsyspri);
}
void
l2arc_stop(void)
{
if (!(spa_mode_global & FWRITE))
return;
mutex_enter(&l2arc_feed_thr_lock);
cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
l2arc_thread_exit = 1;
while (l2arc_thread_exit != 0)
cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
mutex_exit(&l2arc_feed_thr_lock);
}
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