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OpenZFS 9284 - arc_reclaim_thread has 2 jobs

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Following the fix for 9018 (Replace kmem_cache_reap_now() with
kmem_cache_reap_soon), the arc_reclaim_thread() no longer blocks
while reaping.  However, the code is still confusing and error-prone,
because this thread has two responsibilities.  We should instead
separate this into two threads each with their own responsibility:

 1. keep `arc_size` under `arc_c`, by calling `arc_adjust()`, which
    improves `arc_is_overflowing()`

 2. keep enough free memory in the system, by calling
    `arc_kmem_reap_now()` plus `arc_shrink()`, which improves
    `arc_available_memory()`.

Furthermore, we can use the zthr infrastructure to separate the
"should we do something" from "do it" parts of the logic, and
normalize the start up / shut down of the threads.

Authored by: Brad Lewis <brad.lewis@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Dan McDonald <danmcd@joyent.com>
Reviewed by: Tim Kordas <tim.kordas@joyent.com>
Reviewed by: Tim Chase <tim@chase2k.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Ported-by:  Brad Lewis <brad.lewis@delphix.com>
Signed-off-by: Brad Lewis <brad.lewis@delphix.com>

OpenZFS-issue: https://www.illumos.org/issues/9284
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/de753e34f9
Closes #8165
This commit is contained in:
Brad Lewis 2017-03-15 16:41:52 -07:00 committed by Brian Behlendorf
parent 00f198de6b
commit 3ec34e5527
7 changed files with 292 additions and 179 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/spl/sys/kmem.h
View File

@ -163,6 +163,7 @@ extern unsigned int spl_kmem_alloc_max;
#define kmem_alloc(sz, fl) spl_kmem_alloc((sz), (fl), __func__, __LINE__)
#define kmem_zalloc(sz, fl) spl_kmem_zalloc((sz), (fl), __func__, __LINE__)
#define kmem_free(ptr, sz) spl_kmem_free((ptr), (sz))
#define kmem_cache_reap_active spl_kmem_cache_reap_active
extern void *spl_kmem_alloc(size_t sz, int fl, const char *func, int line);
extern void *spl_kmem_zalloc(size_t sz, int fl, const char *func, int line);
@ -181,5 +182,6 @@ extern void spl_kmem_free_track(const void *buf, size_t size);
extern int spl_kmem_init(void);
extern void spl_kmem_fini(void);
extern int spl_kmem_cache_reap_active(void);
#endif /* _SPL_KMEM_H */

1
include/sys/zfs_context.h
View File

@ -773,6 +773,7 @@ typedef int fstrans_cookie_t;
extern fstrans_cookie_t spl_fstrans_mark(void);
extern void spl_fstrans_unmark(fstrans_cookie_t);
extern int __spl_pf_fstrans_check(void);
extern int kmem_cache_reap_active(void);
#define ____cacheline_aligned

4
include/sys/zthr.h
View File

@ -29,6 +29,7 @@ struct zthr {
kmutex_t zthr_lock;
kcondvar_t zthr_cv;
boolean_t zthr_cancel;
hrtime_t zthr_wait_time;
zthr_checkfunc_t *zthr_checkfunc;
zthr_func_t *zthr_func;
@ -38,6 +39,9 @@ struct zthr {
extern zthr_t *zthr_create(zthr_checkfunc_t checkfunc,
zthr_func_t *func, void *arg);
extern zthr_t *zthr_create_timer(zthr_checkfunc_t *checkfunc,
zthr_func_t *func, void *arg, hrtime_t nano_wait);
extern void zthr_exit(zthr_t *t, int rc);
extern void zthr_destroy(zthr_t *t);

6
lib/libzpool/kernel.c
View File

@ -1276,6 +1276,12 @@ __spl_pf_fstrans_check(void)
return (0);
}
int
kmem_cache_reap_active(void)
{
return (0);
}
void *zvol_tag = "zvol_tag";
void

12
module/spl/spl-kmem-cache.c
View File

@ -1732,6 +1732,18 @@ spl_kmem_cache_reap_now(spl_kmem_cache_t *skc, int count)
}
EXPORT_SYMBOL(spl_kmem_cache_reap_now);
/*
* This is stubbed out for code consistency with other platforms. There
* is existing logic to prevent concurrent reaping so while this is ugly
* it should do no harm.
*/
int
spl_kmem_cache_reap_active()
{
return (0);
}
EXPORT_SYMBOL(spl_kmem_cache_reap_active);
/*
* Reap all free slabs from all registered caches.
*/

418
module/zfs/arc.c
View File

@ -20,10 +20,10 @@
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012, Joyent, Inc. All rights reserved.
* Copyright (c) 2018, Joyent, Inc.
* Copyright (c) 2011, 2018 by Delphix. All rights reserved.
* Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
* Copyright 2015 Nexenta Systems, Inc. All rights reserved.
* Copyright 2017 Nexenta Systems, Inc. All rights reserved.
*/
/*
@ -299,7 +299,7 @@
#endif
#include <sys/callb.h>
#include <sys/kstat.h>
#include <sys/dmu_tx.h>
#include <sys/zthr.h>
#include <zfs_fletcher.h>
#include <sys/arc_impl.h>
#include <sys/trace_arc.h>
@ -311,10 +311,22 @@
boolean_t arc_watch = B_FALSE;
#endif
static kmutex_t arc_reclaim_lock;
static kcondvar_t arc_reclaim_thread_cv;
static boolean_t arc_reclaim_thread_exit;
static kcondvar_t arc_reclaim_waiters_cv;
/*
* This thread's job is to keep enough free memory in the system, by
* calling arc_kmem_reap_soon() plus arc_reduce_target_size(), which improves
* arc_available_memory().
*/
static zthr_t *arc_reap_zthr;
/*
* This thread's job is to keep arc_size under arc_c, by calling
* arc_adjust(), which improves arc_is_overflowing().
*/
static zthr_t *arc_adjust_zthr;
static kmutex_t arc_adjust_lock;
static kcondvar_t arc_adjust_waiters_cv;
static boolean_t arc_adjust_needed = B_FALSE;
/*
* The number of headers to evict in arc_evict_state_impl() before
@ -326,20 +338,25 @@ static kcondvar_t arc_reclaim_waiters_cv;
int zfs_arc_evict_batch_limit = 10;
/* number of seconds before growing cache again */
static int arc_grow_retry = 5;
static int arc_grow_retry = 5;
/*
* Minimum time between calls to arc_kmem_reap_soon().
*/
int arc_kmem_cache_reap_retry_ms = 1000;
/* shift of arc_c for calculating overflow limit in arc_get_data_impl */
int zfs_arc_overflow_shift = 8;
int zfs_arc_overflow_shift = 8;
/* shift of arc_c for calculating both min and max arc_p */
static int arc_p_min_shift = 4;
int arc_p_min_shift = 4;
/* log2(fraction of arc to reclaim) */
static int arc_shrink_shift = 7;
static int arc_shrink_shift = 7;
/* percent of pagecache to reclaim arc to */
#ifdef _KERNEL
static uint_t zfs_arc_pc_percent = 0;
static uint_t zfs_arc_pc_percent = 0;
#endif
/*
@ -366,7 +383,10 @@ static int arc_min_prescient_prefetch_ms;
*/
int arc_lotsfree_percent = 10;
static int arc_dead;
/*
* hdr_recl() uses this to determine if the arc is up and running.
*/
static boolean_t arc_initialized;
/*
* The arc has filled available memory and has now warmed up.
@ -906,6 +926,7 @@ aggsum_t astat_bonus_size;
aggsum_t astat_hdr_size;
aggsum_t astat_l2_hdr_size;
static hrtime_t arc_growtime;
static list_t arc_prune_list;
static kmutex_t arc_prune_mtx;
static taskq_t *arc_prune_taskq;
@ -1380,8 +1401,8 @@ 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_thread_cv);
if (arc_initialized)
zthr_wakeup(arc_reap_zthr);
}
static void
@ -4097,13 +4118,14 @@ arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
* function should proceed in this case).
*
* If threads are left sleeping, due to not
* using cv_broadcast, they will be woken up
* just before arc_reclaim_thread() sleeps.
* using cv_broadcast here, they will be woken
* up via cv_broadcast in arc_adjust_cb() just
* before arc_adjust_zthr sleeps.
*/
mutex_enter(&arc_reclaim_lock);
mutex_enter(&arc_adjust_lock);
if (!arc_is_overflowing())
cv_signal(&arc_reclaim_waiters_cv);
mutex_exit(&arc_reclaim_lock);
cv_signal(&arc_adjust_waiters_cv);
mutex_exit(&arc_adjust_lock);
} else {
ARCSTAT_BUMP(arcstat_mutex_miss);
}
@ -4763,8 +4785,8 @@ arc_flush(spa_t *spa, boolean_t retry)
(void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
}
void
arc_shrink(int64_t to_free)
static void
arc_reduce_target_size(int64_t to_free)
{
uint64_t asize = aggsum_value(&arc_size);
uint64_t c = arc_c;
@ -4782,10 +4804,14 @@ arc_shrink(int64_t to_free)
arc_c = arc_c_min;
}
if (asize > arc_c)
(void) arc_adjust();
if (asize > arc_c) {
/* See comment in arc_adjust_cb_check() on why lock+flag */
mutex_enter(&arc_adjust_lock);
arc_adjust_needed = B_TRUE;
mutex_exit(&arc_adjust_lock);
zthr_wakeup(arc_adjust_zthr);
}
}
/*
* Return maximum amount of memory that we could possibly use. Reduced
* to half of all memory in user space which is primarily used for testing.
@ -4989,7 +5015,7 @@ arc_reclaim_needed(void)
}
static void
arc_kmem_reap_now(void)
arc_kmem_reap_soon(void)
{
size_t i;
kmem_cache_t *prev_cache = NULL;
@ -5044,135 +5070,169 @@ arc_kmem_reap_now(void)
}
}
/* ARGSUSED */
static boolean_t
arc_adjust_cb_check(void *arg, zthr_t *zthr)
{
/*
* This is necessary in order to keep the kstat information
* up to date for tools that display kstat data such as the
* mdb ::arc dcmd and the Linux crash utility. These tools
* typically do not call kstat's update function, but simply
* dump out stats from the most recent update. Without
* this call, these commands may show stale stats for the
* anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
* with this change, the data might be up to 1 second
* out of date(the arc_adjust_zthr has a maximum sleep
* time of 1 second); but that should suffice. The
* arc_state_t structures can be queried directly if more
* accurate information is needed.
*/
if (arc_ksp != NULL)
arc_ksp->ks_update(arc_ksp, KSTAT_READ);
/*
* We have to rely on arc_get_data_impl() to tell us when to adjust,
* rather than checking if we are overflowing here, so that we are
* sure to not leave arc_get_data_impl() waiting on
* arc_adjust_waiters_cv. If we have become "not overflowing" since
* arc_get_data_impl() checked, we need to wake it up. We could
* broadcast the CV here, but arc_get_data_impl() may have not yet
* gone to sleep. We would need to use a mutex to ensure that this
* function doesn't broadcast until arc_get_data_impl() has gone to
* sleep (e.g. the arc_adjust_lock). However, the lock ordering of
* such a lock would necessarily be incorrect with respect to the
* zthr_lock, which is held before this function is called, and is
* held by arc_get_data_impl() when it calls zthr_wakeup().
*/
return (arc_adjust_needed);
}
/*
* Threads can block in arc_get_data_impl() waiting for this thread to evict
* enough data and signal them to proceed. When this happens, the threads in
* arc_get_data_impl() are sleeping while holding the hash lock for their
* particular arc header. Thus, we must be careful to never sleep on a
* hash lock in this thread. This is to prevent the following deadlock:
*
* - Thread A sleeps on CV in arc_get_data_impl() holding hash lock "L",
* waiting for the reclaim thread to signal it.
*
* - arc_reclaim_thread() tries to acquire hash lock "L" using mutex_enter,
* fails, and goes to sleep forever.
*
* This possible deadlock is avoided by always acquiring a hash lock
* using mutex_tryenter() from arc_reclaim_thread().
* Keep arc_size under arc_c by running arc_adjust which evicts data
* from the ARC.
*/
/* ARGSUSED */
static void
arc_reclaim_thread(void *unused)
static int
arc_adjust_cb(void *arg, zthr_t *zthr)
{
fstrans_cookie_t cookie = spl_fstrans_mark();
hrtime_t growtime = 0;
callb_cpr_t cpr;
uint64_t evicted = 0;
fstrans_cookie_t cookie = spl_fstrans_mark();
CALLB_CPR_INIT(&cpr, &arc_reclaim_lock, callb_generic_cpr, FTAG);
mutex_enter(&arc_reclaim_lock);
while (!arc_reclaim_thread_exit) {
uint64_t evicted = 0;
uint64_t need_free = arc_need_free;
arc_tuning_update();
/* Evict from cache */
evicted = arc_adjust();
/*
* If evicted is zero, we couldn't evict anything
* via arc_adjust(). This could be due to hash lock
* collisions, but more likely due to the majority of
* arc buffers being unevictable. Therefore, even if
* arc_size is above arc_c, another pass is unlikely to
* be helpful and could potentially cause us to enter an
* infinite loop. Additionally, zthr_iscancelled() is
* checked here so that if the arc is shutting down, the
* broadcast will wake any remaining arc adjust waiters.
*/
mutex_enter(&arc_adjust_lock);
arc_adjust_needed = !zthr_iscancelled(arc_adjust_zthr) &&
evicted > 0 && aggsum_compare(&arc_size, arc_c) > 0;
if (!arc_adjust_needed) {
/*
* This is necessary in order for the mdb ::arc dcmd to
* show up to date information. Since the ::arc command
* does not call the kstat's update function, without
* this call, the command may show stale stats for the
* anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
* with this change, the data might be up to 1 second
* out of date; but that should suffice. The arc_state_t
* structures can be queried directly if more accurate
* information is needed.
* We're either no longer overflowing, or we
* can't evict anything more, so we should wake
* arc_get_data_impl() sooner.
*/
#ifndef __linux__
if (arc_ksp != NULL)
arc_ksp->ks_update(arc_ksp, KSTAT_READ);
#endif
mutex_exit(&arc_reclaim_lock);
cv_broadcast(&arc_adjust_waiters_cv);
arc_need_free = 0;
}
mutex_exit(&arc_adjust_lock);
spl_fstrans_unmark(cookie);
return (0);
}
/* ARGSUSED */
static boolean_t
arc_reap_cb_check(void *arg, zthr_t *zthr)
{
int64_t free_memory = arc_available_memory();
/*
* If a kmem reap is already active, don't schedule more. We must
* check for this because kmem_cache_reap_soon() won't actually
* block on the cache being reaped (this is to prevent callers from
* becoming implicitly blocked by a system-wide kmem reap -- which,
* on a system with many, many full magazines, can take minutes).
*/
if (!kmem_cache_reap_active() && free_memory < 0) {
arc_no_grow = B_TRUE;
arc_warm = B_TRUE;
/*
* We call arc_adjust() before (possibly) calling
* arc_kmem_reap_now(), so that we can wake up
* arc_get_data_buf() sooner.
* Wait at least zfs_grow_retry (default 5) seconds
* before considering growing.
*/
evicted = arc_adjust();
int64_t free_memory = arc_available_memory();
if (free_memory < 0) {
arc_no_grow = B_TRUE;
arc_warm = B_TRUE;
/*
* Wait at least zfs_grow_retry (default 5) seconds
* before considering growing.
*/
growtime = gethrtime() + SEC2NSEC(arc_grow_retry);
arc_kmem_reap_now();
/*
* If we are still low on memory, shrink the ARC
* so that we have arc_shrink_min free space.
*/
free_memory = arc_available_memory();
int64_t to_free =
(arc_c >> arc_shrink_shift) - free_memory;
if (to_free > 0) {
#ifdef _KERNEL
to_free = MAX(to_free, need_free);
#endif
arc_shrink(to_free);
}
} else if (free_memory < arc_c >> arc_no_grow_shift) {
arc_no_grow = B_TRUE;
} else if (gethrtime() >= growtime) {
arc_no_grow = B_FALSE;
}
mutex_enter(&arc_reclaim_lock);
/*
* If evicted is zero, we couldn't evict anything via
* arc_adjust(). This could be due to hash lock
* collisions, but more likely due to the majority of
* arc buffers being unevictable. Therefore, even if
* arc_size is above arc_c, another pass is unlikely to
* be helpful and could potentially cause us to enter an
* infinite loop.
*/
if (aggsum_compare(&arc_size, arc_c) <= 0|| evicted == 0) {
/*
* We're either no longer overflowing, or we
* can't evict anything more, so we should wake
* up any threads before we go to sleep and remove
* the bytes we were working on from arc_need_free
* since nothing more will be done here.
*/
cv_broadcast(&arc_reclaim_waiters_cv);
ARCSTAT_INCR(arcstat_need_free, -need_free);
/*
* Block until signaled, or after one second (we
* might need to perform arc_kmem_reap_now()
* even if we aren't being signalled)
*/
CALLB_CPR_SAFE_BEGIN(&cpr);
(void) cv_timedwait_sig_hires(&arc_reclaim_thread_cv,
&arc_reclaim_lock, SEC2NSEC(1), MSEC2NSEC(1), 0);
CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_lock);
}
arc_growtime = gethrtime() + SEC2NSEC(arc_grow_retry);
return (B_TRUE);
} else if (free_memory < arc_c >> arc_no_grow_shift) {
arc_no_grow = B_TRUE;
} else if (gethrtime() >= arc_growtime) {
arc_no_grow = B_FALSE;
}
arc_reclaim_thread_exit = B_FALSE;
cv_broadcast(&arc_reclaim_thread_cv);
CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_lock */
return (B_FALSE);
}
/*
* Keep enough free memory in the system by reaping the ARC's kmem
* caches. To cause more slabs to be reapable, we may reduce the
* target size of the cache (arc_c), causing the arc_adjust_cb()
* to free more buffers.
*/
/* ARGSUSED */
static int
arc_reap_cb(void *arg, zthr_t *zthr)
{
int64_t free_memory;
fstrans_cookie_t cookie = spl_fstrans_mark();
/*
* Kick off asynchronous kmem_reap()'s of all our caches.
*/
arc_kmem_reap_soon();
/*
* Wait at least arc_kmem_cache_reap_retry_ms between
* arc_kmem_reap_soon() calls. Without this check it is possible to
* end up in a situation where we spend lots of time reaping
* caches, while we're near arc_c_min. Waiting here also gives the
* subsequent free memory check a chance of finding that the
* asynchronous reap has already freed enough memory, and we don't
* need to call arc_reduce_target_size().
*/
delay((hz * arc_kmem_cache_reap_retry_ms + 999) / 1000);
/*
* Reduce the target size as needed to maintain the amount of free
* memory in the system at a fraction of the arc_size (1/128th by
* default). If oversubscribed (free_memory < 0) then reduce the
* target arc_size by the deficit amount plus the fractional
* amount. If free memory is positive but less then the fractional
* amount, reduce by what is needed to hit the fractional amount.
*/
free_memory = arc_available_memory();
int64_t to_free =
(arc_c >> arc_shrink_shift) - free_memory;
if (to_free > 0) {
#ifdef _KERNEL
to_free = MAX(to_free, arc_need_free);
#endif
arc_reduce_target_size(to_free);
}
spl_fstrans_unmark(cookie);
thread_exit();
return (0);
}
#ifdef _KERNEL
@ -5276,21 +5336,21 @@ __arc_shrinker_func(struct shrinker *shrink, struct shrink_control *sc)
return (SHRINK_STOP);
/* Reclaim in progress */
if (mutex_tryenter(&arc_reclaim_lock) == 0) {
if (mutex_tryenter(&arc_adjust_lock) == 0) {
ARCSTAT_INCR(arcstat_need_free, ptob(sc->nr_to_scan));
return (0);
}
mutex_exit(&arc_reclaim_lock);
mutex_exit(&arc_adjust_lock);
/*
* Evict the requested number of pages by shrinking arc_c the
* requested amount.
*/
if (pages > 0) {
arc_shrink(ptob(sc->nr_to_scan));
arc_reduce_target_size(ptob(sc->nr_to_scan));
if (current_is_kswapd())
arc_kmem_reap_now();
arc_kmem_reap_soon();
#ifdef HAVE_SPLIT_SHRINKER_CALLBACK
pages = MAX((int64_t)pages -
(int64_t)btop(arc_evictable_memory()), 0);
@ -5300,7 +5360,7 @@ __arc_shrinker_func(struct shrinker *shrink, struct shrink_control *sc)
/*
* We've shrunk what we can, wake up threads.
*/
cv_broadcast(&arc_reclaim_waiters_cv);
cv_broadcast(&arc_adjust_waiters_cv);
} else
pages = SHRINK_STOP;
@ -5315,7 +5375,7 @@ __arc_shrinker_func(struct shrinker *shrink, struct shrink_control *sc)
ARCSTAT_BUMP(arcstat_memory_indirect_count);
} else {
arc_no_grow = B_TRUE;
arc_kmem_reap_now();
arc_kmem_reap_soon();
ARCSTAT_BUMP(arcstat_memory_direct_count);
}
@ -5369,8 +5429,11 @@ arc_adapt(int bytes, arc_state_t *state)
}
ASSERT((int64_t)arc_p >= 0);
/*
* Wake reap thread if we do not have any available memory
*/
if (arc_reclaim_needed()) {
cv_signal(&arc_reclaim_thread_cv);
zthr_wakeup(arc_reap_zthr);
return;
}
@ -5478,7 +5541,7 @@ arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
* overflowing; thus we don't use a while loop here.
*/
if (arc_is_overflowing()) {
mutex_enter(&arc_reclaim_lock);
mutex_enter(&arc_adjust_lock);
/*
* Now that we've acquired the lock, we may no longer be
@ -5492,11 +5555,12 @@ arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
* shouldn't cause any harm.
*/
if (arc_is_overflowing()) {
cv_signal(&arc_reclaim_thread_cv);
cv_wait(&arc_reclaim_waiters_cv, &arc_reclaim_lock);
arc_adjust_needed = B_TRUE;
zthr_wakeup(arc_adjust_zthr);
(void) cv_wait(&arc_adjust_waiters_cv,
&arc_adjust_lock);
}
mutex_exit(&arc_reclaim_lock);
mutex_exit(&arc_adjust_lock);
}
VERIFY3U(hdr->b_type, ==, type);
@ -7687,10 +7751,8 @@ void
arc_init(void)
{
uint64_t percent, allmem = arc_all_memory();
mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&arc_reclaim_thread_cv, NULL, CV_DEFAULT, NULL);
cv_init(&arc_reclaim_waiters_cv, NULL, CV_DEFAULT, NULL);
mutex_init(&arc_adjust_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&arc_adjust_waiters_cv, NULL, CV_DEFAULT, NULL);
arc_min_prefetch_ms = 1000;
arc_min_prescient_prefetch_ms = 6000;
@ -7750,6 +7812,13 @@ arc_init(void)
arc_c = arc_c_min;
arc_state_init();
/*
* The arc must be "uninitialized", so that hdr_recl() (which is
* registered by buf_init()) will not access arc_reap_zthr before
* it is created.
*/
ASSERT(!arc_initialized);
buf_init();
list_create(&arc_prune_list, sizeof (arc_prune_t),
@ -7759,8 +7828,6 @@ arc_init(void)
arc_prune_taskq = taskq_create("arc_prune", max_ncpus, defclsyspri,
max_ncpus, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
arc_reclaim_thread_exit = B_FALSE;
arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
@ -7770,10 +7837,12 @@ arc_init(void)
kstat_install(arc_ksp);
}
(void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
TS_RUN, defclsyspri);
arc_adjust_zthr = zthr_create(arc_adjust_cb_check,
arc_adjust_cb, NULL);
arc_reap_zthr = zthr_create_timer(arc_reap_cb_check,
arc_reap_cb, NULL, SEC2NSEC(1));
arc_dead = B_FALSE;
arc_initialized = B_TRUE;
arc_warm = B_FALSE;
/*
@ -7805,22 +7874,10 @@ arc_fini(void)
spl_unregister_shrinker(&arc_shrinker);
#endif /* _KERNEL */
mutex_enter(&arc_reclaim_lock);
arc_reclaim_thread_exit = B_TRUE;
/*
* The reclaim thread will set arc_reclaim_thread_exit back to
* B_FALSE when it is finished exiting; we're waiting for that.
*/
while (arc_reclaim_thread_exit) {
cv_signal(&arc_reclaim_thread_cv);
cv_wait(&arc_reclaim_thread_cv, &arc_reclaim_lock);
}
mutex_exit(&arc_reclaim_lock);
/* Use B_TRUE to ensure *all* buffers are evicted */
arc_flush(NULL, B_TRUE);
arc_dead = B_TRUE;
arc_initialized = B_FALSE;
if (arc_ksp != NULL) {
kstat_delete(arc_ksp);
@ -7841,9 +7898,14 @@ arc_fini(void)
list_destroy(&arc_prune_list);
mutex_destroy(&arc_prune_mtx);
mutex_destroy(&arc_reclaim_lock);
cv_destroy(&arc_reclaim_thread_cv);
cv_destroy(&arc_reclaim_waiters_cv);
(void) zthr_cancel(arc_adjust_zthr);
zthr_destroy(arc_adjust_zthr);
(void) zthr_cancel(arc_reap_zthr);
zthr_destroy(arc_reap_zthr);
mutex_destroy(&arc_adjust_lock);
cv_destroy(&arc_adjust_waiters_cv);
/*
* buf_fini() must proceed arc_state_fini() because buf_fin() may

28
module/zfs/zthr.c
View File

@ -47,6 +47,10 @@
* 3] When the zthr is done, it changes the indicator to stopped, allowing
* a new cycle to start.
*
* Besides being awakened by other threads, a zthr can be configured
* during creation to wakeup on its own after a specified interval
* [see zthr_create_timer()].
*
* == ZTHR creation
*
* Every zthr needs three inputs to start running:
@ -74,6 +78,9 @@
*
* To start a zthr:
* zthr_t *zthr_pointer = zthr_create(checkfunc, func, args);
* or
* zthr_t *zthr_pointer = zthr_create_timer(checkfunc, func,
* args, max_sleep);
*
* After that you should be able to wakeup, cancel, and resume the
* zthr from another thread using zthr_pointer.
@ -189,7 +196,13 @@ zthr_procedure(void *arg)
mutex_enter(&t->zthr_lock);
} else {
/* go to sleep */
cv_wait_sig(&t->zthr_cv, &t->zthr_lock);
if (t->zthr_wait_time == 0) {
cv_wait_sig(&t->zthr_cv, &t->zthr_lock);
} else {
(void) cv_timedwait_sig_hires(&t->zthr_cv,
&t->zthr_lock, t->zthr_wait_time,
MSEC2NSEC(1), 0);
}
}
}
mutex_exit(&t->zthr_lock);
@ -199,6 +212,18 @@ zthr_procedure(void *arg)
zthr_t *
zthr_create(zthr_checkfunc_t *checkfunc, zthr_func_t *func, void *arg)
{
return (zthr_create_timer(checkfunc, func, arg, (hrtime_t)0));
}
/*
* Create a zthr with specified maximum sleep time. If the time
* in sleeping state exceeds max_sleep, a wakeup(do the check and
* start working if required) will be triggered.
*/
zthr_t *
zthr_create_timer(zthr_checkfunc_t *checkfunc, zthr_func_t *func,
void *arg, hrtime_t max_sleep)
{
zthr_t *t = kmem_zalloc(sizeof (*t), KM_SLEEP);
mutex_init(&t->zthr_lock, NULL, MUTEX_DEFAULT, NULL);
@ -208,6 +233,7 @@ zthr_create(zthr_checkfunc_t *checkfunc, zthr_func_t *func, void *arg)
t->zthr_checkfunc = checkfunc;
t->zthr_func = func;
t->zthr_arg = arg;
t->zthr_wait_time = max_sleep;
t->zthr_thread = thread_create(NULL, 0, zthr_procedure, t,
0, &p0, TS_RUN, minclsyspri);