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freebsd-nq/module/zfs/arc.c
Brian Behlendorf d7e398ce1a Cleanup ZFS debug infrastructure 
Historically the internal zfs debug infrastructure has been
scattered throughout the code.  Since we expect to start making
more use of this code this patch performs some cleanup.

* Consolidate the zfs debug infrastructure in the zfs_debug.[ch]
  files.  This includes moving the zfs_flags and zfs_recover
  variables, plus moving the zfs_panic_recover() function.

* Remove the existing unused functionality in zfs_debug.c and
  replace it with code which correctly utilized the spl logging
  infrastructure.

* Remove the __dprintf() function from zfs_ioctl.c.  This is
  dead code, the dprintf() functionality in the kernel relies
  on the spl log support.

* Remove dprintf() from hdr_recl().  This wasn't particularly
  useful and was missing the required format specifier anyway.

* Subsequent patches should unify the dprintf() and zfs_dbgmsg()
  functions.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
2012-02-02 11:24:30 -08:00

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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.
*/
/*
* 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 therefor 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 therefor 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 therefor provide two
* types of locks: 1) the hash table lock array, and 2) the
* arc list locks.
*
* Buffers do not have their own mutexs, rather they rely on the
* hash table mutexs for the bulk of their protection (i.e. most
* fields in the arc_buf_hdr_t are protected by these mutexs).
*
* 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.
*
* Arc buffers may have an associated eviction callback function.
* This function will be invoked prior to removing the buffer (e.g.
* in arc_do_user_evicts()). Note however that the data associated
* with the buffer may be evicted prior to the callback. The callback
* must be made with *no locks held* (to prevent deadlock). Additionally,
* the users of callbacks must ensure that their private data is
* protected from simultaneous callbacks from arc_buf_evict()
* and arc_do_user_evicts().
*
* It as also possible to register a callback which is run when the
* arc_meta_limit is reached and no buffers can be safely evicted. In
* this case the arc user should drop a reference on some arc buffers so
* they can be reclaimed and the arc_meta_limit honored. For example,
* when using the ZPL each dentry holds a references on a znode. These
* dentries must be pruned before the arc buffer holding the znode can
* be safely evicted.
*
* Note that the majority of the performance stats are manipulated
* with atomic operations.
*
* The L2ARC uses the l2arc_buflist_mtx global mutex 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
*/
#include <sys/spa.h>
#include <sys/zio.h>
#include <sys/zfs_context.h>
#include <sys/arc.h>
#include <sys/vdev.h>
#include <sys/vdev_impl.h>
#ifdef _KERNEL
#include <sys/vmsystm.h>
#include <vm/anon.h>
#include <sys/fs/swapnode.h>
#include <sys/zpl.h>
#endif
#include <sys/callb.h>
#include <sys/kstat.h>
#include <zfs_fletcher.h>
static kmutex_t arc_reclaim_thr_lock;
static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
static uint8_t arc_thread_exit;
extern int zfs_write_limit_shift;
extern uint64_t zfs_write_limit_max;
extern kmutex_t zfs_write_limit_lock;
/* number of bytes to prune from caches when at arc_meta_limit is reached */
uint_t arc_meta_prune = 1048576;
typedef enum arc_reclaim_strategy {
ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
ARC_RECLAIM_CONS /* Conservative reclaim strategy */
} arc_reclaim_strategy_t;
/* number of seconds before growing cache again */
static int arc_grow_retry = 60;
/* 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 = 5;
/*
* minimum lifespan of a prefetch block in clock ticks
* (initialized in arc_init())
*/
static int arc_min_prefetch_lifespan;
static int arc_dead;
/*
* The arc has filled available memory and has now warmed up.
*/
static boolean_t arc_warm;
/*
* These tunables are for performance analysis.
*/
unsigned long zfs_arc_max = 0;
unsigned long zfs_arc_min = 0;
unsigned long zfs_arc_meta_limit = 0;
int zfs_arc_grow_retry = 0;
int zfs_arc_shrink_shift = 0;
int zfs_arc_p_min_shift = 0;
int zfs_arc_meta_prune = 0;
/*
* 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_t arcs_list[ARC_BUFC_NUMTYPES]; /* list of evictable buffers */
uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
uint64_t arcs_size; /* total amount of data in this state */
kmutex_t arcs_mtx;
} 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_deleted;
kstat_named_t arcstat_recycle_miss;
kstat_named_t arcstat_mutex_miss;
kstat_named_t arcstat_evict_skip;
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_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;
kstat_named_t arcstat_hdr_size;
kstat_named_t arcstat_data_size;
kstat_named_t arcstat_other_size;
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_hdr_miss;
kstat_named_t arcstat_l2_evict_lock_retry;
kstat_named_t arcstat_l2_evict_reading;
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_hdr_size;
kstat_named_t arcstat_memory_throttle_count;
kstat_named_t arcstat_memory_direct_count;
kstat_named_t arcstat_memory_indirect_count;
kstat_named_t arcstat_no_grow;
kstat_named_t arcstat_tempreserve;
kstat_named_t arcstat_loaned_bytes;
kstat_named_t arcstat_prune;
kstat_named_t arcstat_meta_used;
kstat_named_t arcstat_meta_limit;
kstat_named_t arcstat_meta_max;
} 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 },
{ "deleted", KSTAT_DATA_UINT64 },
{ "recycle_miss", KSTAT_DATA_UINT64 },
{ "mutex_miss", KSTAT_DATA_UINT64 },
{ "evict_skip", KSTAT_DATA_UINT64 },
{ "evict_l2_cached", KSTAT_DATA_UINT64 },
{ "evict_l2_eligible", KSTAT_DATA_UINT64 },
{ "evict_l2_ineligible", 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 },
{ "hdr_size", KSTAT_DATA_UINT64 },
{ "data_size", KSTAT_DATA_UINT64 },
{ "other_size", 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_hdr_miss", KSTAT_DATA_UINT64 },
{ "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
{ "l2_evict_reading", 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_hdr_size", KSTAT_DATA_UINT64 },
{ "memory_throttle_count", KSTAT_DATA_UINT64 },
{ "memory_direct_count", KSTAT_DATA_UINT64 },
{ "memory_indirect_count", KSTAT_DATA_UINT64 },
{ "arc_no_grow", KSTAT_DATA_UINT64 },
{ "arc_tempreserve", KSTAT_DATA_UINT64 },
{ "arc_loaned_bytes", KSTAT_DATA_UINT64 },
{ "arc_prune", KSTAT_DATA_UINT64 },
{ "arc_meta_used", KSTAT_DATA_UINT64 },
{ "arc_meta_limit", KSTAT_DATA_UINT64 },
{ "arc_meta_max", 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_no_grow ARCSTAT(arcstat_no_grow)
#define arc_tempreserve ARCSTAT(arcstat_tempreserve)
#define arc_loaned_bytes ARCSTAT(arcstat_loaned_bytes)
#define arc_meta_used ARCSTAT(arcstat_meta_used)
#define arc_meta_limit ARCSTAT(arcstat_meta_limit)
#define arc_meta_max ARCSTAT(arcstat_meta_max)
typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
typedef struct arc_callback arc_callback_t;
struct arc_callback {
void *acb_private;
arc_done_func_t *acb_done;
arc_buf_t *acb_buf;
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_done;
arc_buf_t *awcb_buf;
};
struct arc_buf_hdr {
/* protected by hash lock */
dva_t b_dva;
uint64_t b_birth;
uint64_t b_cksum0;
kmutex_t b_freeze_lock;
zio_cksum_t *b_freeze_cksum;
void *b_thawed;
arc_buf_hdr_t *b_hash_next;
arc_buf_t *b_buf;
uint32_t b_flags;
uint32_t b_datacnt;
arc_callback_t *b_acb;
kcondvar_t b_cv;
/* immutable */
arc_buf_contents_t b_type;
uint64_t b_size;
uint64_t b_spa;
/* protected by arc state mutex */
arc_state_t *b_state;
list_node_t b_arc_node;
/* updated atomically */
clock_t b_arc_access;
/* self protecting */
refcount_t b_refcnt;
l2arc_buf_hdr_t *b_l2hdr;
list_node_t b_l2node;
};
static list_t arc_prune_list;
static kmutex_t arc_prune_mtx;
static arc_buf_t *arc_eviction_list;
static kmutex_t arc_eviction_mtx;
static arc_buf_hdr_t arc_eviction_hdr;
static void arc_get_data_buf(arc_buf_t *buf);
static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
static int arc_evict_needed(arc_buf_contents_t type);
static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
#define GHOST_STATE(state) \
((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
(state) == arc_l2c_only)
/*
* Private ARC flags. These flags are private ARC only flags that will show up
* in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
* be passed in as arc_flags in things like arc_read. However, these flags
* should never be passed and should only be set by ARC code. When adding new
* public flags, make sure not to smash the private ones.
*/
#define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
#define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
#define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
#define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
#define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
#define ARC_INDIRECT (1 << 14) /* this is an indirect block */
#define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
#define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
#define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
#define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
#define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
#define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
#define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
(hdr)->b_l2hdr != NULL)
#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
/*
* Other sizes
*/
#define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
#define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
/*
* Hash table routines
*/
#define HT_LOCK_ALIGN 64
#define HT_LOCK_PAD (P2NPHASE(sizeof (kmutex_t), (HT_LOCK_ALIGN)))
struct ht_lock {
kmutex_t ht_lock;
#ifdef _KERNEL
unsigned char pad[HT_LOCK_PAD];
#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];
} 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 */
#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
*/
unsigned long l2arc_write_max = L2ARC_WRITE_SIZE; /* def max write size */
unsigned long l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra warmup write */
unsigned long l2arc_headroom = L2ARC_HEADROOM; /* # of dev writes */
unsigned long l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
unsigned long l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval msecs */
int l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
int l2arc_feed_again = B_TRUE; /* turbo warmup */
int l2arc_norw = B_TRUE; /* no reads during writes */
/*
* L2ARC Internals
*/
typedef struct l2arc_dev {
vdev_t *l2ad_vdev; /* vdev */
spa_t *l2ad_spa; /* spa */
uint64_t l2ad_hand; /* next write location */
uint64_t l2ad_write; /* desired write size, bytes */
uint64_t l2ad_boost; /* warmup write boost, bytes */
uint64_t l2ad_start; /* first addr on device */
uint64_t l2ad_end; /* last addr on device */
uint64_t l2ad_evict; /* last addr eviction reached */
boolean_t l2ad_first; /* first sweep through */
boolean_t l2ad_writing; /* currently writing */
list_t *l2ad_buflist; /* buffer list */
list_node_t l2ad_node; /* device list node */
} l2arc_dev_t;
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 kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
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_t *l2rcb_buf; /* read buffer */
spa_t *l2rcb_spa; /* spa */
blkptr_t l2rcb_bp; /* original blkptr */
zbookmark_t l2rcb_zb; /* original bookmark */
int l2rcb_flags; /* original flags */
} 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;
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 */
};
typedef struct l2arc_data_free {
/* protected by l2arc_free_on_write_mtx */
void *l2df_data;
size_t l2df_size;
void (*l2df_func)(void *, size_t);
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 l2arc_read_done(zio_t *zio);
static void l2arc_hdr_stat_add(void);
static void l2arc_hdr_stat_remove(void);
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 BUF_EMPTY(buf) \
((buf)->b_dva.dva_word[0] == 0 && \
(buf)->b_dva.dva_word[1] == 0 && \
(buf)->b_birth == 0)
#define BUF_EQUAL(spa, dva, birth, buf) \
((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
((buf)->b_birth == birth) && ((buf)->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;
hdr->b_cksum0 = 0;
}
static arc_buf_hdr_t *
buf_hash_find(uint64_t spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp)
{
uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
arc_buf_hdr_t *buf;
mutex_enter(hash_lock);
for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
buf = buf->b_hash_next) {
if (BUF_EQUAL(spa, dva, birth, buf)) {
*lockp = hash_lock;
return (buf);
}
}
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.
*/
static arc_buf_hdr_t *
buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
{
uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
arc_buf_hdr_t *fbuf;
uint32_t i;
ASSERT(!HDR_IN_HASH_TABLE(buf));
*lockp = hash_lock;
mutex_enter(hash_lock);
for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
fbuf = fbuf->b_hash_next, i++) {
if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
return (fbuf);
}
buf->b_hash_next = buf_hash_table.ht_table[idx];
buf_hash_table.ht_table[idx] = buf;
buf->b_flags |= ARC_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 *buf)
{
arc_buf_hdr_t *fbuf, **bufp;
uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
ASSERT(HDR_IN_HASH_TABLE(buf));
bufp = &buf_hash_table.ht_table[idx];
while ((fbuf = *bufp) != buf) {
ASSERT(fbuf != NULL);
bufp = &fbuf->b_hash_next;
}
*bufp = buf->b_hash_next;
buf->b_hash_next = NULL;
buf->b_flags &= ~ARC_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_cache;
static kmem_cache_t *buf_cache;
static void
buf_fini(void)
{
int i;
#if defined(_KERNEL) && defined(HAVE_SPL)
/* Large allocations which do not require contiguous pages
* should be using vmem_free() in the linux kernel */
vmem_free(buf_hash_table.ht_table,
(buf_hash_table.ht_mask + 1) * sizeof (void *));
#else
kmem_free(buf_hash_table.ht_table,
(buf_hash_table.ht_mask + 1) * sizeof (void *));
#endif
for (i = 0; i < BUF_LOCKS; i++)
mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
kmem_cache_destroy(hdr_cache);
kmem_cache_destroy(buf_cache);
}
/*
* Constructor callback - called when the cache is empty
* and a new buf is requested.
*/
/* ARGSUSED */
static int
hdr_cons(void *vbuf, void *unused, int kmflag)
{
arc_buf_hdr_t *buf = vbuf;
bzero(buf, sizeof (arc_buf_hdr_t));
refcount_create(&buf->b_refcnt);
cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
list_link_init(&buf->b_arc_node);
list_link_init(&buf->b_l2node);
arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
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);
rw_init(&buf->b_data_lock, NULL, RW_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_dest(void *vbuf, void *unused)
{
arc_buf_hdr_t *buf = vbuf;
ASSERT(BUF_EMPTY(buf));
refcount_destroy(&buf->b_refcnt);
cv_destroy(&buf->b_cv);
mutex_destroy(&buf->b_freeze_lock);
arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
}
/* ARGSUSED */
static void
buf_dest(void *vbuf, void *unused)
{
arc_buf_t *buf = vbuf;
mutex_destroy(&buf->b_evict_lock);
rw_destroy(&buf->b_data_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)
{
/*
* 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_thr_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 64K block size. The table will take up
* totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
*/
while (hsize * 65536 < physmem * PAGESIZE)
hsize <<= 1;
retry:
buf_hash_table.ht_mask = hsize - 1;
#if defined(_KERNEL) && defined(HAVE_SPL)
/* Large allocations which do not require contiguous pages
* should be using vmem_alloc() in the linux kernel */
buf_hash_table.ht_table =
vmem_zalloc(hsize * sizeof (void*), KM_SLEEP);
#else
buf_hash_table.ht_table =
kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
#endif
if (buf_hash_table.ht_table == NULL) {
ASSERT(hsize > (1ULL << 8));
hsize >>= 1;
goto retry;
}
hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
0, hdr_cons, hdr_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);
}
}
#define ARC_MINTIME (hz>>4) /* 62 ms */
static void
arc_cksum_verify(arc_buf_t *buf)
{
zio_cksum_t zc;
if (!(zfs_flags & ZFS_DEBUG_MODIFY))
return;
mutex_enter(&buf->b_hdr->b_freeze_lock);
if (buf->b_hdr->b_freeze_cksum == NULL ||
(buf->b_hdr->b_flags & ARC_IO_ERROR)) {
mutex_exit(&buf->b_hdr->b_freeze_lock);
return;
}
fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
panic("buffer modified while frozen!");
mutex_exit(&buf->b_hdr->b_freeze_lock);
}
static int
arc_cksum_equal(arc_buf_t *buf)
{
zio_cksum_t zc;
int equal;
mutex_enter(&buf->b_hdr->b_freeze_lock);
fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
mutex_exit(&buf->b_hdr->b_freeze_lock);
return (equal);
}
static void
arc_cksum_compute(arc_buf_t *buf, boolean_t force)
{
if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
return;
mutex_enter(&buf->b_hdr->b_freeze_lock);
if (buf->b_hdr->b_freeze_cksum != NULL) {
mutex_exit(&buf->b_hdr->b_freeze_lock);
return;
}
buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
buf->b_hdr->b_freeze_cksum);
mutex_exit(&buf->b_hdr->b_freeze_lock);
}
void
arc_buf_thaw(arc_buf_t *buf)
{
if (zfs_flags & ZFS_DEBUG_MODIFY) {
if (buf->b_hdr->b_state != arc_anon)
panic("modifying non-anon buffer!");
if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
panic("modifying buffer while i/o in progress!");
arc_cksum_verify(buf);
}
mutex_enter(&buf->b_hdr->b_freeze_lock);
if (buf->b_hdr->b_freeze_cksum != NULL) {
kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
buf->b_hdr->b_freeze_cksum = NULL;
}
if (zfs_flags & ZFS_DEBUG_MODIFY) {
if (buf->b_hdr->b_thawed)
kmem_free(buf->b_hdr->b_thawed, 1);
buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP);
}
mutex_exit(&buf->b_hdr->b_freeze_lock);
}
void
arc_buf_freeze(arc_buf_t *buf)
{
kmutex_t *hash_lock;
if (!(zfs_flags & ZFS_DEBUG_MODIFY))
return;
hash_lock = HDR_LOCK(buf->b_hdr);
mutex_enter(hash_lock);
ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
buf->b_hdr->b_state == arc_anon);
arc_cksum_compute(buf, B_FALSE);
mutex_exit(hash_lock);
}
static void
add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
{
ASSERT(MUTEX_HELD(hash_lock));
if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
(ab->b_state != arc_anon)) {
uint64_t delta = ab->b_size * ab->b_datacnt;
list_t *list = &ab->b_state->arcs_list[ab->b_type];
uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
ASSERT(!MUTEX_HELD(&ab->b_state->arcs_mtx));
mutex_enter(&ab->b_state->arcs_mtx);
ASSERT(list_link_active(&ab->b_arc_node));
list_remove(list, ab);
if (GHOST_STATE(ab->b_state)) {
ASSERT3U(ab->b_datacnt, ==, 0);
ASSERT3P(ab->b_buf, ==, NULL);
delta = ab->b_size;
}
ASSERT(delta > 0);
ASSERT3U(*size, >=, delta);
atomic_add_64(size, -delta);
mutex_exit(&ab->b_state->arcs_mtx);
/* remove the prefetch flag if we get a reference */
if (ab->b_flags & ARC_PREFETCH)
ab->b_flags &= ~ARC_PREFETCH;
}
}
static int
remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
{
int cnt;
arc_state_t *state = ab->b_state;
ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
ASSERT(!GHOST_STATE(state));
if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
(state != arc_anon)) {
uint64_t *size = &state->arcs_lsize[ab->b_type];
ASSERT(!MUTEX_HELD(&state->arcs_mtx));
mutex_enter(&state->arcs_mtx);
ASSERT(!list_link_active(&ab->b_arc_node));
list_insert_head(&state->arcs_list[ab->b_type], ab);
ASSERT(ab->b_datacnt > 0);
atomic_add_64(size, ab->b_size * ab->b_datacnt);
mutex_exit(&state->arcs_mtx);
}
return (cnt);
}
/*
* Move the supplied buffer to the indicated state. The mutex
* for the buffer must be held by the caller.
*/
static void
arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
{
arc_state_t *old_state = ab->b_state;
int64_t refcnt = refcount_count(&ab->b_refcnt);
uint64_t from_delta, to_delta;
ASSERT(MUTEX_HELD(hash_lock));
ASSERT(new_state != old_state);
ASSERT(refcnt == 0 || ab->b_datacnt > 0);
ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
from_delta = to_delta = ab->b_datacnt * ab->b_size;
/*
* 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) {
int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx);
uint64_t *size = &old_state->arcs_lsize[ab->b_type];
if (use_mutex)
mutex_enter(&old_state->arcs_mtx);
ASSERT(list_link_active(&ab->b_arc_node));
list_remove(&old_state->arcs_list[ab->b_type], ab);
/*
* If prefetching out of the ghost cache,
* we will have a non-zero datacnt.
*/
if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
/* ghost elements have a ghost size */
ASSERT(ab->b_buf == NULL);
from_delta = ab->b_size;
}
ASSERT3U(*size, >=, from_delta);
atomic_add_64(size, -from_delta);
if (use_mutex)
mutex_exit(&old_state->arcs_mtx);
}
if (new_state != arc_anon) {
int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx);
uint64_t *size = &new_state->arcs_lsize[ab->b_type];
if (use_mutex)
mutex_enter(&new_state->arcs_mtx);
list_insert_head(&new_state->arcs_list[ab->b_type], ab);
/* ghost elements have a ghost size */
if (GHOST_STATE(new_state)) {
ASSERT(ab->b_datacnt == 0);
ASSERT(ab->b_buf == NULL);
to_delta = ab->b_size;
}
atomic_add_64(size, to_delta);
if (use_mutex)
mutex_exit(&new_state->arcs_mtx);
}
}
ASSERT(!BUF_EMPTY(ab));
if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
buf_hash_remove(ab);
/* adjust state sizes */
if (to_delta)
atomic_add_64(&new_state->arcs_size, to_delta);
if (from_delta) {
ASSERT3U(old_state->arcs_size, >=, from_delta);
atomic_add_64(&old_state->arcs_size, -from_delta);
}
ab->b_state = new_state;
/* adjust l2arc hdr stats */
if (new_state == arc_l2c_only)
l2arc_hdr_stat_add();
else if (old_state == arc_l2c_only)
l2arc_hdr_stat_remove();
}
void
arc_space_consume(uint64_t space, arc_space_type_t type)
{
ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
switch (type) {
default:
break;
case ARC_SPACE_DATA:
ARCSTAT_INCR(arcstat_data_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;
}
atomic_add_64(&arc_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) {
default:
break;
case ARC_SPACE_DATA:
ARCSTAT_INCR(arcstat_data_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;
}
ASSERT(arc_meta_used >= space);
if (arc_meta_max < arc_meta_used)
arc_meta_max = arc_meta_used;
atomic_add_64(&arc_meta_used, -space);
ASSERT(arc_size >= space);
atomic_add_64(&arc_size, -space);
}
void *
arc_data_buf_alloc(uint64_t size)
{
if (arc_evict_needed(ARC_BUFC_DATA))
cv_signal(&arc_reclaim_thr_cv);
atomic_add_64(&arc_size, size);
return (zio_data_buf_alloc(size));
}
void
arc_data_buf_free(void *buf, uint64_t size)
{
zio_data_buf_free(buf, size);
ASSERT(arc_size >= size);
atomic_add_64(&arc_size, -size);
}
arc_buf_t *
arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
{
arc_buf_hdr_t *hdr;
arc_buf_t *buf;
ASSERT3U(size, >, 0);
hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
ASSERT(BUF_EMPTY(hdr));
hdr->b_size = size;
hdr->b_type = type;
hdr->b_spa = spa_guid(spa);
hdr->b_state = arc_anon;
hdr->b_arc_access = 0;
buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
buf->b_hdr = hdr;
buf->b_data = NULL;
buf->b_efunc = NULL;
buf->b_private = NULL;
buf->b_next = NULL;
hdr->b_buf = buf;
arc_get_data_buf(buf);
hdr->b_datacnt = 1;
hdr->b_flags = 0;
ASSERT(refcount_is_zero(&hdr->b_refcnt));
(void) refcount_add(&hdr->b_refcnt, tag);
return (buf);
}
static char *arc_onloan_tag = "onloan";
/*
* 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, int size)
{
arc_buf_t *buf;
buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
atomic_add_64(&arc_loaned_bytes, size);
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;
ASSERT(buf->b_data != NULL);
(void) refcount_add(&hdr->b_refcnt, tag);
(void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag);
atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
}
/* Detach an arc_buf from a dbuf (tag) */
void
arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
{
arc_buf_hdr_t *hdr;
ASSERT(buf->b_data != NULL);
hdr = buf->b_hdr;
(void) refcount_add(&hdr->b_refcnt, arc_onloan_tag);
(void) refcount_remove(&hdr->b_refcnt, tag);
buf->b_efunc = NULL;
buf->b_private = NULL;
atomic_add_64(&arc_loaned_bytes, hdr->b_size);
}
static arc_buf_t *
arc_buf_clone(arc_buf_t *from)
{
arc_buf_t *buf;
arc_buf_hdr_t *hdr = from->b_hdr;
uint64_t size = hdr->b_size;
ASSERT(hdr->b_state != arc_anon);
buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
buf->b_hdr = hdr;
buf->b_data = NULL;
buf->b_efunc = NULL;
buf->b_private = NULL;
buf->b_next = hdr->b_buf;
hdr->b_buf = buf;
arc_get_data_buf(buf);
bcopy(from->b_data, buf->b_data, size);
hdr->b_datacnt += 1;
return (buf);
}
void
arc_buf_add_ref(arc_buf_t *buf, void* tag)
{
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
/*
* Check to see if this buffer is evicted. Callers
* must verify b_data != NULL to know if the add_ref
* was successful.
*/
mutex_enter(&buf->b_evict_lock);
if (buf->b_data == NULL) {
mutex_exit(&buf->b_evict_lock);
return;
}
hash_lock = HDR_LOCK(buf->b_hdr);
mutex_enter(hash_lock);
hdr = buf->b_hdr;
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
mutex_exit(&buf->b_evict_lock);
ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
add_reference(hdr, hash_lock, tag);
DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
arc_access(hdr, hash_lock);
mutex_exit(hash_lock);
ARCSTAT_BUMP(arcstat_hits);
ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
data, metadata, hits);
}
/*
* Free the arc data buffer. If it is an l2arc write in progress,
* the buffer is placed on l2arc_free_on_write to be freed later.
*/
static void
arc_buf_data_free(arc_buf_hdr_t *hdr, void (*free_func)(void *, size_t),
void *data, size_t size)
{
if (HDR_L2_WRITING(hdr)) {
l2arc_data_free_t *df;
df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
df->l2df_data = data;
df->l2df_size = size;
df->l2df_func = free_func;
mutex_enter(&l2arc_free_on_write_mtx);
list_insert_head(l2arc_free_on_write, df);
mutex_exit(&l2arc_free_on_write_mtx);
ARCSTAT_BUMP(arcstat_l2_free_on_write);
} else {
free_func(data, size);
}
}
static void
arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all)
{
arc_buf_t **bufp;
/* free up data associated with the buf */
if (buf->b_data) {
arc_state_t *state = buf->b_hdr->b_state;
uint64_t size = buf->b_hdr->b_size;
arc_buf_contents_t type = buf->b_hdr->b_type;
arc_cksum_verify(buf);
if (!recycle) {
if (type == ARC_BUFC_METADATA) {
arc_buf_data_free(buf->b_hdr, zio_buf_free,
buf->b_data, size);
arc_space_return(size, ARC_SPACE_DATA);
} else {
ASSERT(type == ARC_BUFC_DATA);
arc_buf_data_free(buf->b_hdr,
zio_data_buf_free, buf->b_data, size);
ARCSTAT_INCR(arcstat_data_size, -size);
atomic_add_64(&arc_size, -size);
}
}
if (list_link_active(&buf->b_hdr->b_arc_node)) {
uint64_t *cnt = &state->arcs_lsize[type];
ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
ASSERT(state != arc_anon);
ASSERT3U(*cnt, >=, size);
atomic_add_64(cnt, -size);
}
ASSERT3U(state->arcs_size, >=, size);
atomic_add_64(&state->arcs_size, -size);
buf->b_data = NULL;
ASSERT(buf->b_hdr->b_datacnt > 0);
buf->b_hdr->b_datacnt -= 1;
}
/* only remove the buf if requested */
if (!all)
return;
/* remove the buf from the hdr list */
for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
continue;
*bufp = buf->b_next;
buf->b_next = NULL;
ASSERT(buf->b_efunc == NULL);
/* clean up the buf */
buf->b_hdr = NULL;
kmem_cache_free(buf_cache, buf);
}
static void
arc_hdr_destroy(arc_buf_hdr_t *hdr)
{
l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
ASSERT(refcount_is_zero(&hdr->b_refcnt));
ASSERT3P(hdr->b_state, ==, arc_anon);
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
if (l2hdr != NULL) {
boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
/*
* To prevent arc_free() and l2arc_evict() from
* attempting to free the same buffer at the same time,
* a FREE_IN_PROGRESS flag is given to arc_free() to
* give it priority. l2arc_evict() can't destroy this
* header while we are waiting on l2arc_buflist_mtx.
*
* The hdr may be removed from l2ad_buflist before we
* grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
*/
if (!buflist_held) {
mutex_enter(&l2arc_buflist_mtx);
l2hdr = hdr->b_l2hdr;
}
if (l2hdr != NULL) {
list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
if (hdr->b_state == arc_l2c_only)
l2arc_hdr_stat_remove();
hdr->b_l2hdr = NULL;
}
if (!buflist_held)
mutex_exit(&l2arc_buflist_mtx);
}
if (!BUF_EMPTY(hdr)) {
ASSERT(!HDR_IN_HASH_TABLE(hdr));
buf_discard_identity(hdr);
}
while (hdr->b_buf) {
arc_buf_t *buf = hdr->b_buf;
if (buf->b_efunc) {
mutex_enter(&arc_eviction_mtx);
mutex_enter(&buf->b_evict_lock);
ASSERT(buf->b_hdr != NULL);
arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
hdr->b_buf = buf->b_next;
buf->b_hdr = &arc_eviction_hdr;
buf->b_next = arc_eviction_list;
arc_eviction_list = buf;
mutex_exit(&buf->b_evict_lock);
mutex_exit(&arc_eviction_mtx);
} else {
arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
}
}
if (hdr->b_freeze_cksum != NULL) {
kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
hdr->b_freeze_cksum = NULL;
}
if (hdr->b_thawed) {
kmem_free(hdr->b_thawed, 1);
hdr->b_thawed = NULL;
}
ASSERT(!list_link_active(&hdr->b_arc_node));
ASSERT3P(hdr->b_hash_next, ==, NULL);
ASSERT3P(hdr->b_acb, ==, NULL);
kmem_cache_free(hdr_cache, hdr);
}
void
arc_buf_free(arc_buf_t *buf, void *tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
int hashed = hdr->b_state != arc_anon;
ASSERT(buf->b_efunc == NULL);
ASSERT(buf->b_data != NULL);
if (hashed) {
kmutex_t *hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
hdr = buf->b_hdr;
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
(void) remove_reference(hdr, hash_lock, tag);
if (hdr->b_datacnt > 1) {
arc_buf_destroy(buf, FALSE, TRUE);
} else {
ASSERT(buf == hdr->b_buf);
ASSERT(buf->b_efunc == NULL);
hdr->b_flags |= ARC_BUF_AVAILABLE;
}
mutex_exit(hash_lock);
} else if (HDR_IO_IN_PROGRESS(hdr)) {
int destroy_hdr;
/*
* We are in the middle of an async write. Don't destroy
* this buffer unless the write completes before we finish
* decrementing the reference count.
*/
mutex_enter(&arc_eviction_mtx);
(void) remove_reference(hdr, NULL, tag);
ASSERT(refcount_is_zero(&hdr->b_refcnt));
destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
mutex_exit(&arc_eviction_mtx);
if (destroy_hdr)
arc_hdr_destroy(hdr);
} else {
if (remove_reference(hdr, NULL, tag) > 0)
arc_buf_destroy(buf, FALSE, TRUE);
else
arc_hdr_destroy(hdr);
}
}
int
arc_buf_remove_ref(arc_buf_t *buf, void* tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
kmutex_t *hash_lock = HDR_LOCK(hdr);
int no_callback = (buf->b_efunc == NULL);
if (hdr->b_state == arc_anon) {
ASSERT(hdr->b_datacnt == 1);
arc_buf_free(buf, tag);
return (no_callback);
}
mutex_enter(hash_lock);
hdr = buf->b_hdr;
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
ASSERT(hdr->b_state != arc_anon);
ASSERT(buf->b_data != NULL);
(void) remove_reference(hdr, hash_lock, tag);
if (hdr->b_datacnt > 1) {
if (no_callback)
arc_buf_destroy(buf, FALSE, TRUE);
} else if (no_callback) {
ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
ASSERT(buf->b_efunc == NULL);
hdr->b_flags |= ARC_BUF_AVAILABLE;
}
ASSERT(no_callback || hdr->b_datacnt > 1 ||
refcount_is_zero(&hdr->b_refcnt));
mutex_exit(hash_lock);
return (no_callback);
}
int
arc_buf_size(arc_buf_t *buf)
{
return (buf->b_hdr->b_size);
}
/*
* Evict buffers from list until we've removed the specified number of
* bytes. Move the removed buffers to the appropriate evict state.
* If the recycle flag is set, then attempt to "recycle" a buffer:
* - look for a buffer to evict that is `bytes' long.
* - return the data block from this buffer rather than freeing it.
* This flag is used by callers that are trying to make space for a
* new buffer in a full arc cache.
*
* 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.
*/
static void *
arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
arc_buf_contents_t type)
{
arc_state_t *evicted_state;
uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
arc_buf_hdr_t *ab, *ab_prev = NULL;
list_t *list = &state->arcs_list[type];
kmutex_t *hash_lock;
boolean_t have_lock;
void *stolen = NULL;
ASSERT(state == arc_mru || state == arc_mfu);
evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
mutex_enter(&state->arcs_mtx);
mutex_enter(&evicted_state->arcs_mtx);
for (ab = list_tail(list); ab; ab = ab_prev) {
ab_prev = list_prev(list, ab);
/* prefetch buffers have a minimum lifespan */
if (HDR_IO_IN_PROGRESS(ab) ||
(spa && ab->b_spa != spa) ||
(ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
ddi_get_lbolt() - ab->b_arc_access <
arc_min_prefetch_lifespan)) {
skipped++;
continue;
}
/* "lookahead" for better eviction candidate */
if (recycle && ab->b_size != bytes &&
ab_prev && ab_prev->b_size == bytes)
continue;
hash_lock = HDR_LOCK(ab);
have_lock = MUTEX_HELD(hash_lock);
if (have_lock || mutex_tryenter(hash_lock)) {
ASSERT3U(refcount_count(&ab->b_refcnt), ==, 0);
ASSERT(ab->b_datacnt > 0);
while (ab->b_buf) {
arc_buf_t *buf = ab->b_buf;
if (!mutex_tryenter(&buf->b_evict_lock)) {
missed += 1;
break;
}
if (buf->b_data) {
bytes_evicted += ab->b_size;
if (recycle && ab->b_type == type &&
ab->b_size == bytes &&
!HDR_L2_WRITING(ab)) {
stolen = buf->b_data;
recycle = FALSE;
}
}
if (buf->b_efunc) {
mutex_enter(&arc_eviction_mtx);
arc_buf_destroy(buf,
buf->b_data == stolen, FALSE);
ab->b_buf = buf->b_next;
buf->b_hdr = &arc_eviction_hdr;
buf->b_next = arc_eviction_list;
arc_eviction_list = buf;
mutex_exit(&arc_eviction_mtx);
mutex_exit(&buf->b_evict_lock);
} else {
mutex_exit(&buf->b_evict_lock);
arc_buf_destroy(buf,
buf->b_data == stolen, TRUE);
}
}
if (ab->b_l2hdr) {
ARCSTAT_INCR(arcstat_evict_l2_cached,
ab->b_size);
} else {
if (l2arc_write_eligible(ab->b_spa, ab)) {
ARCSTAT_INCR(arcstat_evict_l2_eligible,
ab->b_size);
} else {
ARCSTAT_INCR(
arcstat_evict_l2_ineligible,
ab->b_size);
}
}
if (ab->b_datacnt == 0) {
arc_change_state(evicted_state, ab, hash_lock);
ASSERT(HDR_IN_HASH_TABLE(ab));
ab->b_flags |= ARC_IN_HASH_TABLE;
ab->b_flags &= ~ARC_BUF_AVAILABLE;
DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
}
if (!have_lock)
mutex_exit(hash_lock);
if (bytes >= 0 && bytes_evicted >= bytes)
break;
} else {
missed += 1;
}
}
mutex_exit(&evicted_state->arcs_mtx);
mutex_exit(&state->arcs_mtx);
if (bytes_evicted < bytes)
dprintf("only evicted %lld bytes from %x\n",
(longlong_t)bytes_evicted, state);
if (skipped)
ARCSTAT_INCR(arcstat_evict_skip, skipped);
if (missed)
ARCSTAT_INCR(arcstat_mutex_miss, missed);
/*
* We have just evicted some date into the ghost state, make
* sure we also adjust the ghost state size if necessary.
*/
if (arc_no_grow &&
arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size > arc_c) {
int64_t mru_over = arc_anon->arcs_size + arc_mru->arcs_size +
arc_mru_ghost->arcs_size - arc_c;
if (mru_over > 0 && arc_mru_ghost->arcs_lsize[type] > 0) {
int64_t todelete =
MIN(arc_mru_ghost->arcs_lsize[type], mru_over);
arc_evict_ghost(arc_mru_ghost, 0, todelete);
} else if (arc_mfu_ghost->arcs_lsize[type] > 0) {
int64_t todelete = MIN(arc_mfu_ghost->arcs_lsize[type],
arc_mru_ghost->arcs_size +
arc_mfu_ghost->arcs_size - arc_c);
arc_evict_ghost(arc_mfu_ghost, 0, todelete);
}
}
return (stolen);
}
/*
* Remove buffers from list until we've removed the specified number of
* bytes. Destroy the buffers that are removed.
*/
static void
arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
{
arc_buf_hdr_t *ab, *ab_prev;
arc_buf_hdr_t marker;
list_t *list = &state->arcs_list[ARC_BUFC_DATA];
kmutex_t *hash_lock;
uint64_t bytes_deleted = 0;
uint64_t bufs_skipped = 0;
ASSERT(GHOST_STATE(state));
bzero(&marker, sizeof(marker));
top:
mutex_enter(&state->arcs_mtx);
for (ab = list_tail(list); ab; ab = ab_prev) {
ab_prev = list_prev(list, ab);
if (spa && ab->b_spa != spa)
continue;
/* ignore markers */
if (ab->b_spa == 0)
continue;
hash_lock = HDR_LOCK(ab);
/* caller may be trying to modify this buffer, skip it */
if (MUTEX_HELD(hash_lock))
continue;
if (mutex_tryenter(hash_lock)) {
ASSERT(!HDR_IO_IN_PROGRESS(ab));
ASSERT(ab->b_buf == NULL);
ARCSTAT_BUMP(arcstat_deleted);
bytes_deleted += ab->b_size;
if (ab->b_l2hdr != NULL) {
/*
* This buffer is cached on the 2nd Level ARC;
* don't destroy the header.
*/
arc_change_state(arc_l2c_only, ab, hash_lock);
mutex_exit(hash_lock);
} else {
arc_change_state(arc_anon, ab, hash_lock);
mutex_exit(hash_lock);
arc_hdr_destroy(ab);
}
DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
if (bytes >= 0 && bytes_deleted >= bytes)
break;
} else if (bytes < 0) {
/*
* Insert a list marker and then wait for the
* hash lock to become available. Once its
* available, restart from where we left off.
*/
list_insert_after(list, ab, &marker);
mutex_exit(&state->arcs_mtx);
mutex_enter(hash_lock);
mutex_exit(hash_lock);
mutex_enter(&state->arcs_mtx);
ab_prev = list_prev(list, &marker);
list_remove(list, &marker);
} else
bufs_skipped += 1;
}
mutex_exit(&state->arcs_mtx);
if (list == &state->arcs_list[ARC_BUFC_DATA] &&
(bytes < 0 || bytes_deleted < bytes)) {
list = &state->arcs_list[ARC_BUFC_METADATA];
goto top;
}
if (bufs_skipped) {
ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
ASSERT(bytes >= 0);
}
if (bytes_deleted < bytes)
dprintf("only deleted %lld bytes from %p\n",
(longlong_t)bytes_deleted, state);
}
static void
arc_adjust(void)
{
int64_t adjustment, delta;
/*
* Adjust MRU size
*/
adjustment = MIN((int64_t)(arc_size - arc_c),
(int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used -
arc_p));
if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
(void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA);
adjustment -= delta;
}
if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
(void) arc_evict(arc_mru, 0, delta, FALSE,
ARC_BUFC_METADATA);
}
/*
* Adjust MFU size
*/
adjustment = arc_size - arc_c;
if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
(void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA);
adjustment -= delta;
}
if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
int64_t delta = MIN(adjustment,
arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
(void) arc_evict(arc_mfu, 0, delta, FALSE,
ARC_BUFC_METADATA);
}
/*
* Adjust ghost lists
*/
adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
delta = MIN(arc_mru_ghost->arcs_size, adjustment);
arc_evict_ghost(arc_mru_ghost, 0, delta);
}
adjustment =
arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
arc_evict_ghost(arc_mfu_ghost, 0, delta);
}
}
/*
* Request that arc user drop references so that N bytes can be released
* from the cache. This provides a mechanism to ensure the arc can honor
* the arc_meta_limit and reclaim buffers which are pinned in the cache
* by higher layers. (i.e. the zpl)
*/
static void
arc_do_user_prune(int64_t adjustment)
{
arc_prune_func_t *func;
void *private;
arc_prune_t *cp, *np;
mutex_enter(&arc_prune_mtx);
cp = list_head(&arc_prune_list);
while (cp != NULL) {
func = cp->p_pfunc;
private = cp->p_private;
np = list_next(&arc_prune_list, cp);
refcount_add(&cp->p_refcnt, func);
mutex_exit(&arc_prune_mtx);
if (func != NULL)
func(adjustment, private);
mutex_enter(&arc_prune_mtx);
/* User removed prune callback concurrently with execution */
if (refcount_remove(&cp->p_refcnt, func) == 0) {
ASSERT(!list_link_active(&cp->p_node));
refcount_destroy(&cp->p_refcnt);
kmem_free(cp, sizeof (*cp));
}
cp = np;
}
ARCSTAT_BUMP(arcstat_prune);
mutex_exit(&arc_prune_mtx);
}
static void
arc_do_user_evicts(void)
{
mutex_enter(&arc_eviction_mtx);
while (arc_eviction_list != NULL) {
arc_buf_t *buf = arc_eviction_list;
arc_eviction_list = buf->b_next;
mutex_enter(&buf->b_evict_lock);
buf->b_hdr = NULL;
mutex_exit(&buf->b_evict_lock);
mutex_exit(&arc_eviction_mtx);
if (buf->b_efunc != NULL)
VERIFY(buf->b_efunc(buf) == 0);
buf->b_efunc = NULL;
buf->b_private = NULL;
kmem_cache_free(buf_cache, buf);
mutex_enter(&arc_eviction_mtx);
}
mutex_exit(&arc_eviction_mtx);
}
/*
* Evict only meta data objects from the cache leaving the data objects.
* This is only used to enforce the tunable arc_meta_limit, if we are
* unable to evict enough buffers notify the user via the prune callback.
*/
void
arc_adjust_meta(int64_t adjustment, boolean_t may_prune)
{
int64_t delta;
if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_METADATA);
adjustment -= delta;
}
if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
delta = MIN(arc_mfu->arcs_lsize[ARC_BUFC_METADATA], adjustment);
arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_METADATA);
adjustment -= delta;
}
if (may_prune && (adjustment > 0) && (arc_meta_used > arc_meta_limit))
arc_do_user_prune(arc_meta_prune);
}
/*
* Flush all *evictable* data from the cache for the given spa.
* NOTE: this will not touch "active" (i.e. referenced) data.
*/
void
arc_flush(spa_t *spa)
{
uint64_t guid = 0;
if (spa)
guid = spa_guid(spa);
while (list_head(&arc_mru->arcs_list[ARC_BUFC_DATA])) {
(void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
if (spa)
break;
}
while (list_head(&arc_mru->arcs_list[ARC_BUFC_METADATA])) {
(void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
if (spa)
break;
}
while (list_head(&arc_mfu->arcs_list[ARC_BUFC_DATA])) {
(void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
if (spa)
break;
}
while (list_head(&arc_mfu->arcs_list[ARC_BUFC_METADATA])) {
(void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
if (spa)
break;
}
arc_evict_ghost(arc_mru_ghost, guid, -1);
arc_evict_ghost(arc_mfu_ghost, guid, -1);
mutex_enter(&arc_reclaim_thr_lock);
arc_do_user_evicts();
mutex_exit(&arc_reclaim_thr_lock);
ASSERT(spa || arc_eviction_list == NULL);
}
void
arc_shrink(void)
{
if (arc_c > arc_c_min) {
uint64_t to_free;
#ifdef _KERNEL
to_free = MAX(arc_c >> arc_shrink_shift, ptob(needfree));
#else
to_free = arc_c >> arc_shrink_shift;
#endif
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);
ASSERT(arc_c >= arc_c_min);
ASSERT((int64_t)arc_p >= 0);
}
if (arc_size > arc_c)
arc_adjust();
}
static int
arc_reclaim_needed(void)
{
#ifdef _KERNEL
uint64_t extra;
if (needfree)
return (1);
/*
* take 'desfree' extra pages, so we reclaim sooner, rather than later
*/
extra = desfree;
/*
* 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.
*/
if (freemem < lotsfree + needfree + extra)
return (1);
/*
* 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.
*/
if (availrmem < swapfs_minfree + swapfs_reserve + extra)
return (1);
#if defined(__i386)
/*
* 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)
*/
if (btop(vmem_size(heap_arena, VMEM_FREE)) <
(btop(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2))
return (1);
#endif
#else
if (spa_get_random(100) == 0)
return (1);
#endif
return (0);
}
static void
arc_kmem_reap_now(arc_reclaim_strategy_t strat)
{
size_t i;
kmem_cache_t *prev_cache = NULL;
kmem_cache_t *prev_data_cache = NULL;
extern kmem_cache_t *zio_buf_cache[];
extern kmem_cache_t *zio_data_buf_cache[];
/*
* An aggressive reclamation will shrink the cache size as well as
* reap free buffers from the arc kmem caches.
*/
if (strat == ARC_RECLAIM_AGGR)
arc_shrink();
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_cache);
}
static void
arc_reclaim_thread(void)
{
clock_t growtime = 0;
arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
callb_cpr_t cpr;
int64_t prune;
CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
mutex_enter(&arc_reclaim_thr_lock);
while (arc_thread_exit == 0) {
if (arc_reclaim_needed()) {
if (arc_no_grow) {
if (last_reclaim == ARC_RECLAIM_CONS) {
last_reclaim = ARC_RECLAIM_AGGR;
} else {
last_reclaim = ARC_RECLAIM_CONS;
}
} else {
arc_no_grow = TRUE;
last_reclaim = ARC_RECLAIM_AGGR;
membar_producer();
}
/* reset the growth delay for every reclaim */
growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
arc_kmem_reap_now(last_reclaim);
arc_warm = B_TRUE;
} else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
arc_no_grow = FALSE;
}
/*
* Keep meta data usage within limits, arc_shrink() is not
* used to avoid collapsing the arc_c value when only the
* arc_meta_limit is being exceeded.
*/
prune = (int64_t)arc_meta_used - (int64_t)arc_meta_limit;
if (prune > 0)
arc_adjust_meta(prune, B_TRUE);
arc_adjust();
if (arc_eviction_list != NULL)
arc_do_user_evicts();
/* block until needed, or one second, whichever is shorter */
CALLB_CPR_SAFE_BEGIN(&cpr);
(void) cv_timedwait_interruptible(&arc_reclaim_thr_cv,
&arc_reclaim_thr_lock, (ddi_get_lbolt() + hz));
CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
}
arc_thread_exit = 0;
cv_broadcast(&arc_reclaim_thr_cv);
CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
thread_exit();
}
#ifdef _KERNEL
/*
* Under Linux the arc shrinker may be called for synchronous (direct)
* reclaim, or asynchronous (indirect) reclaim. When called by kswapd
* for indirect reclaim we take a conservative approach and just reap
* free slabs from the ARC caches. If this proves to be insufficient
* direct reclaim will be trigger. In direct reclaim a more aggressive
* strategy is used, data is evicted from the ARC and free slabs reaped.
*/
static int
__arc_shrinker_func(struct shrinker *shrink, struct shrink_control *sc)
{
arc_reclaim_strategy_t strategy;
int arc_reclaim;
/* Return number of reclaimable pages based on arc_shrink_shift */
arc_reclaim = MAX(btop(((int64_t)arc_size - (int64_t)arc_c_min))
>> arc_shrink_shift, 0);
if (sc->nr_to_scan == 0)
return (arc_reclaim);
/* Prevent reclaim below arc_c_min */
if (arc_reclaim <= 0)
return (-1);
/* Not allowed to perform filesystem reclaim */
if (!(sc->gfp_mask & __GFP_FS))
return (-1);
/* Reclaim in progress */
if (mutex_tryenter(&arc_reclaim_thr_lock) == 0)
return (-1);
if (current_is_kswapd()) {
strategy = ARC_RECLAIM_CONS;
ARCSTAT_INCR(arcstat_memory_indirect_count, 1);
} else {
strategy = ARC_RECLAIM_AGGR;
ARCSTAT_INCR(arcstat_memory_direct_count, 1);
}
arc_kmem_reap_now(strategy);
arc_reclaim = MAX(btop(((int64_t)arc_size - (int64_t)arc_c_min))
>> arc_shrink_shift, 0);
mutex_exit(&arc_reclaim_thr_lock);
return (arc_reclaim);
}
SPL_SHRINKER_CALLBACK_WRAPPER(arc_shrinker_func);
SPL_SHRINKER_DECLARE(arc_shrinker, arc_shrinker_func, DEFAULT_SEEKS);
#endif /* _KERNEL */
/*
* 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);
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 = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_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 = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_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_thr_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)) {
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 the cache has reached its limits and eviction is required
* prior to insert.
*/
static int
arc_evict_needed(arc_buf_contents_t type)
{
if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
return (1);
#ifdef _KERNEL
/*
* If zio data pages are being allocated out of a separate heap segment,
* then enforce that the size of available vmem for this area remains
* above about 1/32nd free.
*/
if (type == ARC_BUFC_DATA && zio_arena != NULL &&
vmem_size(zio_arena, VMEM_FREE) <
(vmem_size(zio_arena, VMEM_ALLOC) >> 5))
return (1);
#endif
if (arc_reclaim_needed())
return (1);
return (arc_size > arc_c);
}
/*
* The buffer, supplied as the first argument, needs a data block.
* So, if we are at cache max, determine which cache should be victimized.
* We have the following cases:
*
* 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
* In this situation if we're out of space, but the resident size of the MFU is
* under the limit, victimize the MFU cache to satisfy this insertion request.
*
* 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
* Here, we've used up all of the available space for the MRU, so we need to
* evict from our own cache instead. Evict from the set of resident MRU
* entries.
*
* 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
* c minus p represents the MFU space in the cache, since p is the size of the
* cache that is dedicated to the MRU. In this situation there's still space on
* the MFU side, so the MRU side needs to be victimized.
*
* 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
* MFU's resident set is consuming more space than it has been allotted. In
* this situation, we must victimize our own cache, the MFU, for this insertion.
*/
static void
arc_get_data_buf(arc_buf_t *buf)
{
arc_state_t *state = buf->b_hdr->b_state;
uint64_t size = buf->b_hdr->b_size;
arc_buf_contents_t type = buf->b_hdr->b_type;
arc_adapt(size, state);
/*
* We have not yet reached cache maximum size,
* just allocate a new buffer.
*/
if (!arc_evict_needed(type)) {
if (type == ARC_BUFC_METADATA) {
buf->b_data = zio_buf_alloc(size);
arc_space_consume(size, ARC_SPACE_DATA);
} else {
ASSERT(type == ARC_BUFC_DATA);
buf->b_data = zio_data_buf_alloc(size);
ARCSTAT_INCR(arcstat_data_size, size);
atomic_add_64(&arc_size, size);
}
goto out;
}
/*
* If we are prefetching from the mfu ghost list, this buffer
* will end up on the mru list; so steal space from there.
*/
if (state == arc_mfu_ghost)
state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
else if (state == arc_mru_ghost)
state = arc_mru;
if (state == arc_mru || state == arc_anon) {
uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
state = (arc_mfu->arcs_lsize[type] >= size &&
arc_p > mru_used) ? arc_mfu : arc_mru;
} else {
/* MFU cases */
uint64_t mfu_space = arc_c - arc_p;
state = (arc_mru->arcs_lsize[type] >= size &&
mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
}
if ((buf->b_data = arc_evict(state, 0, size, TRUE, type)) == NULL) {
if (type == ARC_BUFC_METADATA) {
buf->b_data = zio_buf_alloc(size);
arc_space_consume(size, ARC_SPACE_DATA);
/*
* If we are unable to recycle an existing meta buffer
* signal the reclaim thread. It will notify users
* via the prune callback to drop references. The
* prune callback in run in the context of the reclaim
* thread to avoid deadlocking on the hash_lock.
*/
cv_signal(&arc_reclaim_thr_cv);
} else {
ASSERT(type == ARC_BUFC_DATA);
buf->b_data = zio_data_buf_alloc(size);
ARCSTAT_INCR(arcstat_data_size, size);
atomic_add_64(&arc_size, size);
}
ARCSTAT_BUMP(arcstat_recycle_miss);
}
ASSERT(buf->b_data != NULL);
out:
/*
* Update the state size. Note that ghost states have a
* "ghost size" and so don't need to be updated.
*/
if (!GHOST_STATE(buf->b_hdr->b_state)) {
arc_buf_hdr_t *hdr = buf->b_hdr;
atomic_add_64(&hdr->b_state->arcs_size, size);
if (list_link_active(&hdr->b_arc_node)) {
ASSERT(refcount_is_zero(&hdr->b_refcnt));
atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
}
/*
* 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_state == arc_anon &&
arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
arc_p = MIN(arc_c, arc_p + size);
}
}
/*
* 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 *buf, kmutex_t *hash_lock)
{
clock_t now;
ASSERT(MUTEX_HELD(hash_lock));
if (buf->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.
*/
ASSERT(buf->b_arc_access == 0);
buf->b_arc_access = ddi_get_lbolt();
DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
arc_change_state(arc_mru, buf, hash_lock);
} else if (buf->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 ((buf->b_flags & ARC_PREFETCH) != 0) {
if (refcount_count(&buf->b_refcnt) == 0) {
ASSERT(list_link_active(&buf->b_arc_node));
} else {
buf->b_flags &= ~ARC_PREFETCH;
ARCSTAT_BUMP(arcstat_mru_hits);
}
buf->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 > buf->b_arc_access + ARC_MINTIME) {
/*
* More than 125ms have passed since we
* instantiated this buffer. Move it to the
* most frequently used state.
*/
buf->b_arc_access = now;
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
arc_change_state(arc_mfu, buf, hash_lock);
}
ARCSTAT_BUMP(arcstat_mru_hits);
} else if (buf->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 (buf->b_flags & ARC_PREFETCH) {
new_state = arc_mru;
if (refcount_count(&buf->b_refcnt) > 0)
buf->b_flags &= ~ARC_PREFETCH;
DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
} else {
new_state = arc_mfu;
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
}
buf->b_arc_access = ddi_get_lbolt();
arc_change_state(new_state, buf, hash_lock);
ARCSTAT_BUMP(arcstat_mru_ghost_hits);
} else if (buf->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 ((buf->b_flags & ARC_PREFETCH) != 0) {
ASSERT(refcount_count(&buf->b_refcnt) == 0);
ASSERT(list_link_active(&buf->b_arc_node));
}
ARCSTAT_BUMP(arcstat_mfu_hits);
buf->b_arc_access = ddi_get_lbolt();
} else if (buf->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 (buf->b_flags & ARC_PREFETCH) {
/*
* This is a prefetch access...
* move this block back to the MRU state.
*/
ASSERT3U(refcount_count(&buf->b_refcnt), ==, 0);
new_state = arc_mru;
}
buf->b_arc_access = ddi_get_lbolt();
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
arc_change_state(new_state, buf, hash_lock);
ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
} else if (buf->b_state == arc_l2c_only) {
/*
* This buffer is on the 2nd Level ARC.
*/
buf->b_arc_access = ddi_get_lbolt();
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
arc_change_state(arc_mfu, buf, 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, buf->b_hdr->b_size);
VERIFY(arc_buf_remove_ref(buf, arg) == 1);
}
/* 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) {
VERIFY(arc_buf_remove_ref(buf, arg) == 1);
*bufp = NULL;
} else {
*bufp = buf;
ASSERT(buf->b_data);
}
}
static void
arc_read_done(zio_t *zio)
{
arc_buf_hdr_t *hdr, *found;
arc_buf_t *buf;
arc_buf_t *abuf; /* buffer we're assigning to callback */
kmutex_t *hash_lock;
arc_callback_t *callback_list, *acb;
int freeable = FALSE;
buf = zio->io_private;
hdr = buf->b_hdr;
/*
* 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.
*/
found = buf_hash_find(hdr->b_spa, &hdr->b_dva, hdr->b_birth,
&hash_lock);
ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && hash_lock == NULL) ||
(found == hdr && DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
(found == hdr && HDR_L2_READING(hdr)));
hdr->b_flags &= ~ARC_L2_EVICTED;
if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
hdr->b_flags &= ~ARC_L2CACHE;
/* byteswap if necessary */
callback_list = hdr->b_acb;
ASSERT(callback_list != NULL);
if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
byteswap_uint64_array :
dmu_ot[BP_GET_TYPE(zio->io_bp)].ot_byteswap;
func(buf->b_data, hdr->b_size);
}
arc_cksum_compute(buf, B_FALSE);
if (hash_lock && zio->io_error == 0 && hdr->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);
}
/* create copies of the data buffer for the callers */
abuf = buf;
for (acb = callback_list; acb; acb = acb->acb_next) {
if (acb->acb_done) {
if (abuf == NULL)
abuf = arc_buf_clone(buf);
acb->acb_buf = abuf;
abuf = NULL;
}
}
hdr->b_acb = NULL;
hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
ASSERT(!HDR_BUF_AVAILABLE(hdr));
if (abuf == buf) {
ASSERT(buf->b_efunc == NULL);
ASSERT(hdr->b_datacnt == 1);
hdr->b_flags |= ARC_BUF_AVAILABLE;
}
ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
if (zio->io_error != 0) {
hdr->b_flags |= ARC_IO_ERROR;
if (hdr->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_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_cv);
if (hash_lock) {
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_state, ==, arc_anon);
freeable = refcount_is_zero(&hdr->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 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.
*
* Normal callers should use arc_read and pass the arc buffer and offset
* for the bp. But if you know you don't need locking, you can use
* arc_read_bp.
*/
int
arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_buf_t *pbuf,
arc_done_func_t *done, void *private, int priority, int zio_flags,
uint32_t *arc_flags, const zbookmark_t *zb)
{
int err;
if (pbuf == NULL) {
/*
* XXX This happens from traverse callback funcs, for
* the objset_phys_t block.
*/
return (arc_read_nolock(pio, spa, bp, done, private, priority,
zio_flags, arc_flags, zb));
}
ASSERT(!refcount_is_zero(&pbuf->b_hdr->b_refcnt));
ASSERT3U((char *)bp - (char *)pbuf->b_data, <, pbuf->b_hdr->b_size);
rw_enter(&pbuf->b_data_lock, RW_READER);
err = arc_read_nolock(pio, spa, bp, done, private, priority,
zio_flags, arc_flags, zb);
rw_exit(&pbuf->b_data_lock);
return (err);
}
int
arc_read_nolock(zio_t *pio, spa_t *spa, const blkptr_t *bp,
arc_done_func_t *done, void *private, int priority, int zio_flags,
uint32_t *arc_flags, const zbookmark_t *zb)
{
arc_buf_hdr_t *hdr;
arc_buf_t *buf = NULL;
kmutex_t *hash_lock;
zio_t *rzio;
uint64_t guid = spa_guid(spa);
top:
hdr = buf_hash_find(guid, BP_IDENTITY(bp), BP_PHYSICAL_BIRTH(bp),
&hash_lock);
if (hdr && hdr->b_datacnt > 0) {
*arc_flags |= ARC_CACHED;
if (HDR_IO_IN_PROGRESS(hdr)) {
if (*arc_flags & ARC_WAIT) {
cv_wait(&hdr->b_cv, hash_lock);
mutex_exit(hash_lock);
goto top;
}
ASSERT(*arc_flags & ARC_NOWAIT);
if (done) {
arc_callback_t *acb = NULL;
acb = kmem_zalloc(sizeof (arc_callback_t),
KM_PUSHPAGE);
acb->acb_done = done;
acb->acb_private = private;
if (pio != NULL)
acb->acb_zio_dummy = zio_null(pio,
spa, NULL, NULL, NULL, zio_flags);
ASSERT(acb->acb_done != NULL);
acb->acb_next = hdr->b_acb;
hdr->b_acb = acb;
add_reference(hdr, hash_lock, private);
mutex_exit(hash_lock);
return (0);
}
mutex_exit(hash_lock);
return (0);
}
ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
if (done) {
add_reference(hdr, hash_lock, private);
/*
* If this block is already in use, create a new
* copy of the data so that we will be guaranteed
* that arc_release() will always succeed.
*/
buf = hdr->b_buf;
ASSERT(buf);
ASSERT(buf->b_data);
if (HDR_BUF_AVAILABLE(hdr)) {
ASSERT(buf->b_efunc == NULL);
hdr->b_flags &= ~ARC_BUF_AVAILABLE;
} else {
buf = arc_buf_clone(buf);
}
} else if (*arc_flags & ARC_PREFETCH &&
refcount_count(&hdr->b_refcnt) == 0) {
hdr->b_flags |= ARC_PREFETCH;
}
DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
arc_access(hdr, hash_lock);
if (*arc_flags & ARC_L2CACHE)
hdr->b_flags |= ARC_L2CACHE;
mutex_exit(hash_lock);
ARCSTAT_BUMP(arcstat_hits);
ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
data, metadata, hits);
if (done)
done(NULL, buf, private);
} else {
uint64_t size = BP_GET_LSIZE(bp);
arc_callback_t *acb;
vdev_t *vd = NULL;
uint64_t addr = -1;
boolean_t devw = B_FALSE;
if (hdr == NULL) {
/* this block is not in the cache */
arc_buf_hdr_t *exists;
arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
buf = arc_buf_alloc(spa, size, private, type);
hdr = buf->b_hdr;
hdr->b_dva = *BP_IDENTITY(bp);
hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
exists = buf_hash_insert(hdr, &hash_lock);
if (exists) {
/* somebody beat us to the hash insert */
mutex_exit(hash_lock);
buf_discard_identity(hdr);
(void) arc_buf_remove_ref(buf, private);
goto top; /* restart the IO request */
}
/* if this is a prefetch, we don't have a reference */
if (*arc_flags & ARC_PREFETCH) {
(void) remove_reference(hdr, hash_lock,
private);
hdr->b_flags |= ARC_PREFETCH;
}
if (*arc_flags & ARC_L2CACHE)
hdr->b_flags |= ARC_L2CACHE;
if (BP_GET_LEVEL(bp) > 0)
hdr->b_flags |= ARC_INDIRECT;
} else {
/* this block is in the ghost cache */
ASSERT(GHOST_STATE(hdr->b_state));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
ASSERT3U(refcount_count(&hdr->b_refcnt), ==, 0);
ASSERT(hdr->b_buf == NULL);
/* if this is a prefetch, we don't have a reference */
if (*arc_flags & ARC_PREFETCH)
hdr->b_flags |= ARC_PREFETCH;
else
add_reference(hdr, hash_lock, private);
if (*arc_flags & ARC_L2CACHE)
hdr->b_flags |= ARC_L2CACHE;
buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
buf->b_hdr = hdr;
buf->b_data = NULL;
buf->b_efunc = NULL;
buf->b_private = NULL;
buf->b_next = NULL;
hdr->b_buf = buf;
ASSERT(hdr->b_datacnt == 0);
hdr->b_datacnt = 1;
arc_get_data_buf(buf);
arc_access(hdr, hash_lock);
}
ASSERT(!GHOST_STATE(hdr->b_state));
acb = kmem_zalloc(sizeof (arc_callback_t), KM_PUSHPAGE);
acb->acb_done = done;
acb->acb_private = private;
ASSERT(hdr->b_acb == NULL);
hdr->b_acb = acb;
hdr->b_flags |= ARC_IO_IN_PROGRESS;
if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL &&
(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;
}
mutex_exit(hash_lock);
ASSERT3U(hdr->b_size, ==, size);
DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
uint64_t, size, zbookmark_t *, zb);
ARCSTAT_BUMP(arcstat_misses);
ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
data, metadata, misses);
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->b_l2hdr != NULL &&
!HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
!(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
l2arc_read_callback_t *cb;
DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
ARCSTAT_BUMP(arcstat_l2_hits);
cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
KM_PUSHPAGE);
cb->l2rcb_buf = buf;
cb->l2rcb_spa = spa;
cb->l2rcb_bp = *bp;
cb->l2rcb_zb = *zb;
cb->l2rcb_flags = zio_flags;
/*
* l2arc read. The SCL_L2ARC lock will be
* released by l2arc_read_done().
*/
rzio = zio_read_phys(pio, vd, addr, size,
buf->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_NOWAIT) {
zio_nowait(rzio);
return (0);
}
ASSERT(*arc_flags & ARC_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, buf->b_data, size,
arc_read_done, buf, priority, zio_flags, zb);
if (*arc_flags & ARC_WAIT)
return (zio_wait(rzio));
ASSERT(*arc_flags & ARC_NOWAIT);
zio_nowait(rzio);
}
return (0);
}
arc_prune_t *
arc_add_prune_callback(arc_prune_func_t *func, void *private)
{
arc_prune_t *p;
p = kmem_alloc(sizeof(*p), KM_SLEEP);
p->p_pfunc = func;
p->p_private = private;
list_link_init(&p->p_node);
refcount_create(&p->p_refcnt);
mutex_enter(&arc_prune_mtx);
refcount_add(&p->p_refcnt, &arc_prune_list);
list_insert_head(&arc_prune_list, p);
mutex_exit(&arc_prune_mtx);
return (p);
}
void
arc_remove_prune_callback(arc_prune_t *p)
{
mutex_enter(&arc_prune_mtx);
list_remove(&arc_prune_list, p);
if (refcount_remove(&p->p_refcnt, &arc_prune_list) == 0) {
refcount_destroy(&p->p_refcnt);
kmem_free(p, sizeof (*p));
}
mutex_exit(&arc_prune_mtx);
}
void
arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
{
ASSERT(buf->b_hdr != NULL);
ASSERT(buf->b_hdr->b_state != arc_anon);
ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
ASSERT(buf->b_efunc == NULL);
ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
buf->b_efunc = func;
buf->b_private = private;
}
/*
* This is used by the DMU to let the ARC know that a buffer is
* being evicted, so the ARC should clean up. If this arc buf
* is not yet in the evicted state, it will be put there.
*/
int
arc_buf_evict(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
arc_buf_t **bufp;
mutex_enter(&buf->b_evict_lock);
hdr = buf->b_hdr;
if (hdr == NULL) {
/*
* We are in arc_do_user_evicts().
*/
ASSERT(buf->b_data == NULL);
mutex_exit(&buf->b_evict_lock);
return (0);
} else if (buf->b_data == NULL) {
arc_buf_t copy = *buf; /* structure assignment */
/*
* We are on the eviction list; process this buffer now
* but let arc_do_user_evicts() do the reaping.
*/
buf->b_efunc = NULL;
mutex_exit(&buf->b_evict_lock);
VERIFY(copy.b_efunc(&copy) == 0);
return (1);
}
hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
hdr = buf->b_hdr;
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
/*
* Pull this buffer off of the hdr
*/
bufp = &hdr->b_buf;
while (*bufp != buf)
bufp = &(*bufp)->b_next;
*bufp = buf->b_next;
ASSERT(buf->b_data != NULL);
arc_buf_destroy(buf, FALSE, FALSE);
if (hdr->b_datacnt == 0) {
arc_state_t *old_state = hdr->b_state;
arc_state_t *evicted_state;
ASSERT(hdr->b_buf == NULL);
ASSERT(refcount_is_zero(&hdr->b_refcnt));
evicted_state =
(old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
mutex_enter(&old_state->arcs_mtx);
mutex_enter(&evicted_state->arcs_mtx);
arc_change_state(evicted_state, hdr, hash_lock);
ASSERT(HDR_IN_HASH_TABLE(hdr));
hdr->b_flags |= ARC_IN_HASH_TABLE;
hdr->b_flags &= ~ARC_BUF_AVAILABLE;
mutex_exit(&evicted_state->arcs_mtx);
mutex_exit(&old_state->arcs_mtx);
}
mutex_exit(hash_lock);
mutex_exit(&buf->b_evict_lock);
VERIFY(buf->b_efunc(buf) == 0);
buf->b_efunc = NULL;
buf->b_private = NULL;
buf->b_hdr = NULL;
buf->b_next = NULL;
kmem_cache_free(buf_cache, buf);
return (1);
}
/*
* Release this buffer from the cache. 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;
kmutex_t *hash_lock = NULL;
l2arc_buf_hdr_t *l2hdr;
uint64_t buf_size = 0;
/*
* 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);
hdr = buf->b_hdr;
/* this buffer is not on any list */
ASSERT(refcount_count(&hdr->b_refcnt) > 0);
if (hdr->b_state == arc_anon) {
/* this buffer is already released */
ASSERT(buf->b_efunc == NULL);
} else {
hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
hdr = buf->b_hdr;
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
}
l2hdr = hdr->b_l2hdr;
if (l2hdr) {
mutex_enter(&l2arc_buflist_mtx);
hdr->b_l2hdr = NULL;
buf_size = hdr->b_size;
}
/*
* Do we have more than one buf?
*/
if (hdr->b_datacnt > 1) {
arc_buf_hdr_t *nhdr;
arc_buf_t **bufp;
uint64_t blksz = hdr->b_size;
uint64_t spa = hdr->b_spa;
arc_buf_contents_t type = hdr->b_type;
uint32_t flags = hdr->b_flags;
ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
/*
* Pull the data off of this hdr and attach it to
* a new anonymous hdr.
*/
(void) remove_reference(hdr, hash_lock, tag);
bufp = &hdr->b_buf;
while (*bufp != buf)
bufp = &(*bufp)->b_next;
*bufp = buf->b_next;
buf->b_next = NULL;
ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
if (refcount_is_zero(&hdr->b_refcnt)) {
uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
ASSERT3U(*size, >=, hdr->b_size);
atomic_add_64(size, -hdr->b_size);
}
hdr->b_datacnt -= 1;
arc_cksum_verify(buf);
mutex_exit(hash_lock);
nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
nhdr->b_size = blksz;
nhdr->b_spa = spa;
nhdr->b_type = type;
nhdr->b_buf = buf;
nhdr->b_state = arc_anon;
nhdr->b_arc_access = 0;
nhdr->b_flags = flags & ARC_L2_WRITING;
nhdr->b_l2hdr = NULL;
nhdr->b_datacnt = 1;
nhdr->b_freeze_cksum = NULL;
(void) refcount_add(&nhdr->b_refcnt, tag);
buf->b_hdr = nhdr;
mutex_exit(&buf->b_evict_lock);
atomic_add_64(&arc_anon->arcs_size, blksz);
} else {
mutex_exit(&buf->b_evict_lock);
ASSERT(refcount_count(&hdr->b_refcnt) == 1);
ASSERT(!list_link_active(&hdr->b_arc_node));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
if (hdr->b_state != arc_anon)
arc_change_state(arc_anon, hdr, hash_lock);
hdr->b_arc_access = 0;
if (hash_lock)
mutex_exit(hash_lock);
buf_discard_identity(hdr);
arc_buf_thaw(buf);
}
buf->b_efunc = NULL;
buf->b_private = NULL;
if (l2hdr) {
list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
ARCSTAT_INCR(arcstat_l2_size, -buf_size);
mutex_exit(&l2arc_buflist_mtx);
}
}
/*
* Release this buffer. If it does not match the provided BP, fill it
* with that block's contents.
*/
/* ARGSUSED */
int
arc_release_bp(arc_buf_t *buf, void *tag, blkptr_t *bp, spa_t *spa,
zbookmark_t *zb)
{
arc_release(buf, tag);
return (0);
}
int
arc_released(arc_buf_t *buf)
{
int released;
mutex_enter(&buf->b_evict_lock);
released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
mutex_exit(&buf->b_evict_lock);
return (released);
}
int
arc_has_callback(arc_buf_t *buf)
{
int callback;
mutex_enter(&buf->b_evict_lock);
callback = (buf->b_efunc != NULL);
mutex_exit(&buf->b_evict_lock);
return (callback);
}
#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_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;
ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
callback->awcb_ready(zio, buf, callback->awcb_private);
/*
* If the IO is already in progress, then this is a re-write
* attempt, so we need to thaw and re-compute the cksum.
* It is the responsibility of the callback to handle the
* accounting for any re-write attempt.
*/
if (HDR_IO_IN_PROGRESS(hdr)) {
mutex_enter(&hdr->b_freeze_lock);
if (hdr->b_freeze_cksum != NULL) {
kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
hdr->b_freeze_cksum = NULL;
}
mutex_exit(&hdr->b_freeze_lock);
}
arc_cksum_compute(buf, B_FALSE);
hdr->b_flags |= ARC_IO_IN_PROGRESS;
}
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;
ASSERT(hdr->b_acb == NULL);
if (zio->io_error == 0) {
hdr->b_dva = *BP_IDENTITY(zio->io_bp);
hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
} else {
ASSERT(BUF_EMPTY(hdr));
}
/*
* If the block to be written was all-zero, we may have
* compressed it away. In this case no write was performed
* so there will be no dva/birth/checksum. The buffer must
* therefore remain anonymous (and uncached).
*/
if (!BUF_EMPTY(hdr)) {
arc_buf_hdr_t *exists;
kmutex_t *hash_lock;
ASSERT(zio->io_error == 0);
arc_cksum_verify(buf);
exists = buf_hash_insert(hdr, &hash_lock);
if (exists) {
/*
* 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_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 {
/* Dedup */
ASSERT(hdr->b_datacnt == 1);
ASSERT(hdr->b_state == arc_anon);
ASSERT(BP_GET_DEDUP(zio->io_bp));
ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
}
}
hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
/* if it's not anon, we are doing a scrub */
if (!exists && hdr->b_state == arc_anon)
arc_access(hdr, hash_lock);
mutex_exit(hash_lock);
} else {
hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
}
ASSERT(!refcount_is_zero(&hdr->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 *done, void *private,
int priority, int zio_flags, const zbookmark_t *zb)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
arc_write_callback_t *callback;
zio_t *zio;
ASSERT(ready != NULL);
ASSERT(done != NULL);
ASSERT(!HDR_IO_ERROR(hdr));
ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
ASSERT(hdr->b_acb == NULL);
if (l2arc)
hdr->b_flags |= ARC_L2CACHE;
callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
callback->awcb_ready = ready;
callback->awcb_done = done;
callback->awcb_private = private;
callback->awcb_buf = buf;
zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
arc_write_ready, arc_write_done, callback, priority, zio_flags, zb);
return (zio);
}
static int
arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, 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)
available_memory =
MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
#endif
if (available_memory >= zfs_write_limit_max)
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 == proc_pageout) {
if (page_load > MAX(ptob(minfree), available_memory) / 4)
return (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 (EAGAIN);
}
page_load = 0;
if (arc_size > arc_c_min) {
uint64_t evictable_memory =
arc_mru->arcs_lsize[ARC_BUFC_DATA] +
arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
available_memory += MIN(evictable_memory, arc_size - arc_c_min);
}
if (inflight_data > available_memory / 4) {
ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
return (ERESTART);
}
#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;
#ifdef ZFS_DEBUG
/*
* Once in a while, fail for no reason. Everything should cope.
*/
if (spa_get_random(10000) == 0) {
dprintf("forcing random failure\n");
return (ERESTART);
}
#endif
if (reserve > arc_c/4 && !arc_no_grow)
arc_c = MIN(arc_c_max, reserve * 4);
if (reserve > arc_c)
return (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.
*/
anon_size = MAX((int64_t)(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 therefor need to
* make sure that there is sufficient available memory for this.
*/
if ((error = arc_memory_throttle(reserve, anon_size, txg)))
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) {
dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
"anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
arc_tempreserve>>10,
arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
reserve>>10, arc_c>>10);
return (ERESTART);
}
atomic_add_64(&arc_tempreserve, reserve);
return (0);
}
void
arc_init(void)
{
mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
/* Convert seconds to clock ticks */
arc_min_prefetch_lifespan = 1 * hz;
/* Start out with 1/8 of all memory */
arc_c = physmem * PAGESIZE / 8;
#ifdef _KERNEL
/*
* On architectures where the physical memory can be larger
* than the addressable space (intel in 32-bit mode), we may
* need to limit the cache to 1/8 of VM size.
*/
arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
/*
* Register a shrinker to support synchronous (direct) memory
* reclaim from the arc. This is done to prevent kswapd from
* swapping out pages when it is preferable to shrink the arc.
*/
spl_register_shrinker(&arc_shrinker);
#endif
/* set min cache to 1/32 of all memory, or 64MB, whichever is more */
arc_c_min = MAX(arc_c / 4, 64<<20);
/* set max to 1/2 of all memory, or all but 4GB, whichever is more */
if (arc_c * 8 >= ((uint64_t)4<<30))
arc_c_max = (arc_c * 8) - ((uint64_t)4<<30);
else
arc_c_max = arc_c_min;
arc_c_max = MAX(arc_c * 4, arc_c_max);
/*
* Allow the tunables to override our calculations if they are
* reasonable (ie. over 64MB)
*/
if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE)
arc_c_max = zfs_arc_max;
if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max)
arc_c_min = zfs_arc_min;
arc_c = arc_c_max;
arc_p = (arc_c >> 1);
/* limit meta-data to 1/4 of the arc capacity */
arc_meta_limit = arc_c_max / 4;
arc_meta_max = 0;
/* 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_grow_retry > 0)
arc_grow_retry = zfs_arc_grow_retry;
if (zfs_arc_shrink_shift > 0)
arc_shrink_shift = zfs_arc_shrink_shift;
if (zfs_arc_p_min_shift > 0)
arc_p_min_shift = zfs_arc_p_min_shift;
if (zfs_arc_meta_prune > 0)
arc_meta_prune = zfs_arc_meta_prune;
/* 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;
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_size = 0;
mutex_init(&arc_anon->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&arc_mru->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&arc_mru_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&arc_mfu->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&arc_mfu_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&arc_l2c_only->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
list_create(&arc_mru->arcs_list[ARC_BUFC_METADATA],
sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc_mru->arcs_list[ARC_BUFC_DATA],
sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA],
sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA],
sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA],
sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc_mfu->arcs_list[ARC_BUFC_DATA],
sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA],
sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA],
sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA],
sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
buf_init();
arc_thread_exit = 0;
list_create(&arc_prune_list, sizeof (arc_prune_t),
offsetof(arc_prune_t, p_node));
arc_eviction_list = NULL;
mutex_init(&arc_prune_mtx, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
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;
kstat_install(arc_ksp);
}
(void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
TS_RUN, minclsyspri);
arc_dead = FALSE;
arc_warm = B_FALSE;
if (zfs_write_limit_max == 0)
zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift;
else
zfs_write_limit_shift = 0;
mutex_init(&zfs_write_limit_lock, NULL, MUTEX_DEFAULT, NULL);
}
void
arc_fini(void)
{
arc_prune_t *p;
mutex_enter(&arc_reclaim_thr_lock);
#ifdef _KERNEL
spl_unregister_shrinker(&arc_shrinker);
#endif /* _KERNEL */
arc_thread_exit = 1;
while (arc_thread_exit != 0)
cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
mutex_exit(&arc_reclaim_thr_lock);
arc_flush(NULL);
arc_dead = TRUE;
if (arc_ksp != NULL) {
kstat_delete(arc_ksp);
arc_ksp = NULL;
}
mutex_enter(&arc_prune_mtx);
while ((p = list_head(&arc_prune_list)) != NULL) {
list_remove(&arc_prune_list, p);
refcount_remove(&p->p_refcnt, &arc_prune_list);
refcount_destroy(&p->p_refcnt);
kmem_free(p, sizeof (*p));
}
mutex_exit(&arc_prune_mtx);
list_destroy(&arc_prune_list);
mutex_destroy(&arc_prune_mtx);
mutex_destroy(&arc_eviction_mtx);
mutex_destroy(&arc_reclaim_thr_lock);
cv_destroy(&arc_reclaim_thr_cv);
list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
mutex_destroy(&arc_anon->arcs_mtx);
mutex_destroy(&arc_mru->arcs_mtx);
mutex_destroy(&arc_mru_ghost->arcs_mtx);
mutex_destroy(&arc_mfu->arcs_mtx);
mutex_destroy(&arc_mfu_ghost->arcs_mtx);
mutex_destroy(&arc_l2c_only->arcs_mtx);
mutex_destroy(&zfs_write_limit_lock);
buf_fini();
ASSERT(arc_loaned_bytes == 0);
}
/*
* 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. 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_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 *ab)
{
/*
* 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 (ab->b_spa != spa_guid || ab->b_l2hdr != NULL ||
HDR_IO_IN_PROGRESS(ab) || !HDR_L2CACHE(ab))
return (B_FALSE);
return (B_TRUE);
}
static uint64_t
l2arc_write_size(l2arc_dev_t *dev)
{
uint64_t size;
size = dev->l2ad_write;
if (arc_warm == B_FALSE)
size += dev->l2ad_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);
}
static void
l2arc_hdr_stat_add(void)
{
ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
}
static void
l2arc_hdr_stat_remove(void)
{
ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
}
/*
* 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(void)
{
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);
ASSERT(df->l2df_data != NULL);
ASSERT(df->l2df_func != NULL);
df->l2df_func(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, *ab, *ab_prev;
l2arc_buf_hdr_t *abl2;
kmutex_t *hash_lock;
cb = zio->io_private;
ASSERT(cb != NULL);
dev = cb->l2wcb_dev;
ASSERT(dev != NULL);
head = cb->l2wcb_head;
ASSERT(head != NULL);
buflist = dev->l2ad_buflist;
ASSERT(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);
mutex_enter(&l2arc_buflist_mtx);
/*
* All writes completed, or an error was hit.
*/
for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
ab_prev = list_prev(buflist, ab);
hash_lock = HDR_LOCK(ab);
if (!mutex_tryenter(hash_lock)) {
/*
* This buffer misses out. It may be in a stage
* of eviction. Its ARC_L2_WRITING flag will be
* left set, denying reads to this buffer.
*/
ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
continue;
}
if (zio->io_error != 0) {
/*
* Error - drop L2ARC entry.
*/
list_remove(buflist, ab);
abl2 = ab->b_l2hdr;
ab->b_l2hdr = NULL;
kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
}
/*
* Allow ARC to begin reads to this L2ARC entry.
*/
ab->b_flags &= ~ARC_L2_WRITING;
mutex_exit(hash_lock);
}
atomic_inc_64(&l2arc_writes_done);
list_remove(buflist, head);
kmem_cache_free(hdr_cache, head);
mutex_exit(&l2arc_buflist_mtx);
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;
arc_buf_t *buf;
kmutex_t *hash_lock;
int equal;
ASSERT(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;
ASSERT(cb != NULL);
buf = cb->l2rcb_buf;
ASSERT(buf != NULL);
hash_lock = HDR_LOCK(buf->b_hdr);
mutex_enter(hash_lock);
hdr = buf->b_hdr;
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
/*
* Check this survived the L2ARC journey.
*/
equal = arc_cksum_equal(buf);
if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
mutex_exit(hash_lock);
zio->io_private = buf;
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 */
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 = EIO;
}
if (!equal)
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, cb->l2rcb_spa, &cb->l2rcb_bp,
buf->b_data, zio->io_size, arc_read_done, buf,
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 list_t *
l2arc_list_locked(int list_num, kmutex_t **lock)
{
list_t *list = NULL;
ASSERT(list_num >= 0 && list_num <= 3);
switch (list_num) {
case 0:
list = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
*lock = &arc_mfu->arcs_mtx;
break;
case 1:
list = &arc_mru->arcs_list[ARC_BUFC_METADATA];
*lock = &arc_mru->arcs_mtx;
break;
case 2:
list = &arc_mfu->arcs_list[ARC_BUFC_DATA];
*lock = &arc_mfu->arcs_mtx;
break;
case 3:
list = &arc_mru->arcs_list[ARC_BUFC_DATA];
*lock = &arc_mru->arcs_mtx;
break;
}
ASSERT(!(MUTEX_HELD(*lock)));
mutex_enter(*lock);
return (list);
}
/*
* 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;
l2arc_buf_hdr_t *abl2;
arc_buf_hdr_t *ab, *ab_prev;
kmutex_t *hash_lock;
uint64_t taddr;
buflist = dev->l2ad_buflist;
if (buflist == NULL)
return;
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(&l2arc_buflist_mtx);
for (ab = list_tail(buflist); ab; ab = ab_prev) {
ab_prev = list_prev(buflist, ab);
hash_lock = HDR_LOCK(ab);
if (!mutex_tryenter(hash_lock)) {
/*
* Missed the hash lock. Retry.
*/
ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
mutex_exit(&l2arc_buflist_mtx);
mutex_enter(hash_lock);
mutex_exit(hash_lock);
goto top;
}
if (HDR_L2_WRITE_HEAD(ab)) {
/*
* We hit a write head node. Leave it for
* l2arc_write_done().
*/
list_remove(buflist, ab);
mutex_exit(hash_lock);
continue;
}
if (!all && ab->b_l2hdr != NULL &&
(ab->b_l2hdr->b_daddr > taddr ||
ab->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;
}
if (HDR_FREE_IN_PROGRESS(ab)) {
/*
* Already on the path to destruction.
*/
mutex_exit(hash_lock);
continue;
}
if (ab->b_state == arc_l2c_only) {
ASSERT(!HDR_L2_READING(ab));
/*
* 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, ab, hash_lock);
arc_hdr_destroy(ab);
} else {
/*
* Invalidate issued or about to be issued
* reads, since we may be about to write
* over this location.
*/
if (HDR_L2_READING(ab)) {
ARCSTAT_BUMP(arcstat_l2_evict_reading);
ab->b_flags |= ARC_L2_EVICTED;
}
/*
* Tell ARC this no longer exists in L2ARC.
*/
if (ab->b_l2hdr != NULL) {
abl2 = ab->b_l2hdr;
ab->b_l2hdr = NULL;
kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
}
list_remove(buflist, ab);
/*
* This may have been leftover after a
* failed write.
*/
ab->b_flags &= ~ARC_L2_WRITING;
}
mutex_exit(hash_lock);
}
mutex_exit(&l2arc_buflist_mtx);
vdev_space_update(dev->l2ad_vdev, -(taddr - dev->l2ad_evict), 0, 0);
dev->l2ad_evict = taddr;
}
/*
* Find and write ARC buffers to the L2ARC device.
*
* An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
* for reading until they have completed writing.
*/
static uint64_t
l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
{
arc_buf_hdr_t *ab, *ab_prev, *head;
l2arc_buf_hdr_t *hdrl2;
list_t *list;
uint64_t passed_sz, write_sz, buf_sz, headroom;
void *buf_data;
kmutex_t *hash_lock, *list_lock = NULL;
boolean_t have_lock, full;
l2arc_write_callback_t *cb;
zio_t *pio, *wzio;
uint64_t guid = spa_guid(spa);
int try;
ASSERT(dev->l2ad_vdev != NULL);
pio = NULL;
write_sz = 0;
full = B_FALSE;
head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
head->b_flags |= ARC_L2_WRITE_HEAD;
/*
* Copy buffers for L2ARC writing.
*/
mutex_enter(&l2arc_buflist_mtx);
for (try = 0; try <= 3; try++) {
list = l2arc_list_locked(try, &list_lock);
passed_sz = 0;
/*
* L2ARC fast warmup.
*
* Until the ARC is warm and starts to evict, read from the
* head of the ARC lists rather than the tail.
*/
headroom = target_sz * l2arc_headroom;
if (arc_warm == B_FALSE)
ab = list_head(list);
else
ab = list_tail(list);
for (; ab; ab = ab_prev) {
if (arc_warm == B_FALSE)
ab_prev = list_next(list, ab);
else
ab_prev = list_prev(list, ab);
hash_lock = HDR_LOCK(ab);
have_lock = MUTEX_HELD(hash_lock);
if (!have_lock && !mutex_tryenter(hash_lock)) {
/*
* Skip this buffer rather than waiting.
*/
continue;
}
passed_sz += ab->b_size;
if (passed_sz > headroom) {
/*
* Searched too far.
*/
mutex_exit(hash_lock);
break;
}
if (!l2arc_write_eligible(guid, ab)) {
mutex_exit(hash_lock);
continue;
}
if ((write_sz + ab->b_size) > target_sz) {
full = B_TRUE;
mutex_exit(hash_lock);
break;
}
if (pio == NULL) {
/*
* Insert a dummy header on the buflist so
* l2arc_write_done() can find where the
* write buffers begin without searching.
*/
list_insert_head(dev->l2ad_buflist, head);
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);
}
/*
* Create and add a new L2ARC header.
*/
hdrl2 = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
hdrl2->b_dev = dev;
hdrl2->b_daddr = dev->l2ad_hand;
ab->b_flags |= ARC_L2_WRITING;
ab->b_l2hdr = hdrl2;
list_insert_head(dev->l2ad_buflist, ab);
buf_data = ab->b_buf->b_data;
buf_sz = ab->b_size;
/*
* Compute and store the buffer cksum before
* writing. On debug the cksum is verified first.
*/
arc_cksum_verify(ab->b_buf);
arc_cksum_compute(ab->b_buf, B_TRUE);
mutex_exit(hash_lock);
wzio = zio_write_phys(pio, dev->l2ad_vdev,
dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
ZIO_FLAG_CANFAIL, B_FALSE);
DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
zio_t *, wzio);
(void) zio_nowait(wzio);
/*
* Keep the clock hand suitably device-aligned.
*/
buf_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
write_sz += buf_sz;
dev->l2ad_hand += buf_sz;
}
mutex_exit(list_lock);
if (full == B_TRUE)
break;
}
mutex_exit(&l2arc_buflist_mtx);
if (pio == NULL) {
ASSERT3U(write_sz, ==, 0);
kmem_cache_free(hdr_cache, head);
return (0);
}
ASSERT3U(write_sz, <=, target_sz);
ARCSTAT_BUMP(arcstat_l2_writes_sent);
ARCSTAT_INCR(arcstat_l2_write_bytes, write_sz);
ARCSTAT_INCR(arcstat_l2_size, write_sz);
vdev_space_update(dev->l2ad_vdev, write_sz, 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)) {
vdev_space_update(dev->l2ad_vdev,
dev->l2ad_end - dev->l2ad_hand, 0, 0);
dev->l2ad_hand = dev->l2ad_start;
dev->l2ad_evict = dev->l2ad_start;
dev->l2ad_first = B_FALSE;
}
dev->l2ad_writing = B_TRUE;
(void) zio_wait(pio);
dev->l2ad_writing = B_FALSE;
return (write_sz);
}
/*
* This thread feeds the L2ARC at regular intervals. This is the beating
* heart of the L2ARC.
*/
static void
l2arc_feed_thread(void)
{
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_interruptible(&l2arc_feed_thr_cv,
&l2arc_feed_thr_lock, next);
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;
ASSERT(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(dev);
/*
* 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));
/*
* 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_write = l2arc_write_max;
adddev->l2ad_boost = l2arc_write_boost;
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_evict = adddev->l2ad_start;
adddev->l2ad_first = B_TRUE;
adddev->l2ad_writing = B_FALSE;
list_link_init(&adddev->l2ad_node);
ASSERT3U(adddev->l2ad_write, >, 0);
/*
* This is a list of all ARC buffers that are still valid on the
* device.
*/
adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l2node));
vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
/*
* 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;
}
}
ASSERT(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);
kmem_free(remdev->l2ad_buflist, sizeof (list_t));
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_buflist_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_buflist_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);
}
#if defined(_KERNEL) && defined(HAVE_SPL)
EXPORT_SYMBOL(arc_read);
EXPORT_SYMBOL(arc_buf_remove_ref);
EXPORT_SYMBOL(arc_getbuf_func);
EXPORT_SYMBOL(arc_add_prune_callback);
EXPORT_SYMBOL(arc_remove_prune_callback);
module_param(zfs_arc_min, ulong, 0444);
MODULE_PARM_DESC(zfs_arc_min, "Min arc size");
module_param(zfs_arc_max, ulong, 0444);
MODULE_PARM_DESC(zfs_arc_max, "Max arc size");
module_param(zfs_arc_meta_limit, ulong, 0444);
MODULE_PARM_DESC(zfs_arc_meta_limit, "Meta limit for arc size");
module_param(zfs_arc_meta_prune, int, 0444);
MODULE_PARM_DESC(zfs_arc_meta_prune, "Bytes of meta data to prune");
module_param(zfs_arc_grow_retry, int, 0444);
MODULE_PARM_DESC(zfs_arc_grow_retry, "Seconds before growing arc size");
module_param(zfs_arc_shrink_shift, int, 0444);
MODULE_PARM_DESC(zfs_arc_shrink_shift, "log2(fraction of arc to reclaim)");
module_param(zfs_arc_p_min_shift, int, 0444);
MODULE_PARM_DESC(zfs_arc_p_min_shift, "arc_c shift to calc min/max arc_p");
module_param(l2arc_write_max, ulong, 0444);
MODULE_PARM_DESC(l2arc_write_max, "Max write bytes per interval");
module_param(l2arc_write_boost, ulong, 0444);
MODULE_PARM_DESC(l2arc_write_boost, "Extra write bytes during device warmup");
module_param(l2arc_headroom, ulong, 0444);
MODULE_PARM_DESC(l2arc_headroom, "Number of max device writes to precache");
module_param(l2arc_feed_secs, ulong, 0444);
MODULE_PARM_DESC(l2arc_feed_secs, "Seconds between L2ARC writing");
module_param(l2arc_feed_min_ms, ulong, 0444);
MODULE_PARM_DESC(l2arc_feed_min_ms, "Min feed interval in milliseconds");
module_param(l2arc_noprefetch, int, 0444);
MODULE_PARM_DESC(l2arc_noprefetch, "Skip caching prefetched buffers");
module_param(l2arc_feed_again, int, 0444);
MODULE_PARM_DESC(l2arc_feed_again, "Turbo L2ARC warmup");
module_param(l2arc_norw, int, 0444);
MODULE_PARM_DESC(l2arc_norw, "No reads during writes");
#endif
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