4034947 anon_swap_adjust() should call kmem_reap() if availrmem is low.
/*
* 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 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
/*
* DVA-based Adjustable Relpacement 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 slowes the flow of new data
* into the cache until we can make space avaiable.
*
* 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 preasure 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() inerface
* 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 "top" state mutex must be held before the "bot" 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().
*
* Note that the majority of the performance stats are manipulated
* with atomic operations.
*/
#include <sys/spa.h>
#include <sys/zio.h>
#include <sys/zfs_context.h>
#include <sys/arc.h>
#include <sys/refcount.h>
#ifdef _KERNEL
#include <sys/vmsystm.h>
#include <vm/anon.h>
#include <sys/fs/swapnode.h>
#include <sys/dnlc.h>
#endif
#include <sys/callb.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;
#define ARC_REDUCE_DNLC_PERCENT 3
uint_t arc_reduce_dnlc_percent = ARC_REDUCE_DNLC_PERCENT;
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;
static kmutex_t arc_reclaim_lock;
static int arc_dead;
/*
* Note that buffers can be on one of 5 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
* When there are no active references to the buffer, they
* are linked onto one of the lists in arc. These are the
* only buffers that can be evicted or deleted.
*
* 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.
*/
typedef struct arc_state {
list_t list; /* linked list of evictable buffer in state */
uint64_t lsize; /* total size of buffers in the linked list */
uint64_t size; /* total size of all buffers in this state */
uint64_t hits;
kmutex_t mtx;
} arc_state_t;
/* The 5 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 struct arc {
arc_state_t *anon;
arc_state_t *mru;
arc_state_t *mru_ghost;
arc_state_t *mfu;
arc_state_t *mfu_ghost;
uint64_t size; /* Actual total arc size */
uint64_t p; /* Target size (in bytes) of mru */
uint64_t c; /* Target size of cache (in bytes) */
uint64_t c_min; /* Minimum target cache size */
uint64_t c_max; /* Maximum target cache size */
/* performance stats */
uint64_t hits;
uint64_t misses;
uint64_t deleted;
uint64_t skipped;
uint64_t hash_elements;
uint64_t hash_elements_max;
uint64_t hash_collisions;
uint64_t hash_chains;
uint32_t hash_chain_max;
int no_grow; /* Don't try to grow cache size */
} arc;
static uint64_t arc_tempreserve;
typedef struct arc_callback arc_callback_t;
struct arc_callback {
arc_done_func_t *acb_done;
void *acb_private;
arc_byteswap_func_t *acb_byteswap;
arc_buf_t *acb_buf;
zio_t *acb_zio_dummy;
arc_callback_t *acb_next;
};
struct arc_buf_hdr {
/* immutable */
uint64_t b_size;
spa_t *b_spa;
/* protected by hash lock */
dva_t b_dva;
uint64_t b_birth;
uint64_t b_cksum0;
arc_buf_hdr_t *b_hash_next;
arc_buf_t *b_buf;
uint32_t b_flags;
uint32_t b_datacnt;
kcondvar_t b_cv;
arc_callback_t *b_acb;
/* 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;
};
static arc_buf_t *arc_eviction_list;
static kmutex_t arc_eviction_mtx;
static void arc_access_and_exit(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
#define GHOST_STATE(state) \
((state) == arc.mru_ghost || (state) == arc.mfu_ghost)
/*
* 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 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_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
/*
* Hash table routines
*/
#define HT_LOCK_PAD 64
struct ht_lock {
kmutex_t ht_lock;
#ifdef _KERNEL
unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
#endif
};
#define BUF_LOCKS 256
typedef struct buf_hash_table {
uint64_t ht_mask;
arc_buf_hdr_t **ht_table;
struct ht_lock ht_locks[BUF_LOCKS];
} 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(buf) \
(BUF_HASH_LOCK(BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth)))
uint64_t zfs_crc64_table[256];
static uint64_t
buf_hash(spa_t *spa, dva_t *dva, uint64_t birth)
{
uintptr_t spav = (uintptr_t)spa;
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 ^= (spav>>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 arc_buf_hdr_t *
buf_hash_find(spa_t *spa, 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 *fbufs[4]; /* XXX to find 6341326 */
static kthread_t *fbufs_lastthread;
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 max, i;
ASSERT(!HDR_IN_HASH_TABLE(buf));
fbufs_lastthread = curthread;
*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 (i < sizeof (fbufs) / sizeof (fbufs[0]))
fbufs[i] = fbuf;
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) {
atomic_add_64(&arc.hash_collisions, 1);
if (i == 1)
atomic_add_64(&arc.hash_chains, 1);
}
while (i > (max = arc.hash_chain_max) &&
max != atomic_cas_32(&arc.hash_chain_max, max, i)) {
continue;
}
atomic_add_64(&arc.hash_elements, 1);
if (arc.hash_elements > arc.hash_elements_max)
atomic_add_64(&arc.hash_elements_max, 1);
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 */
atomic_add_64(&arc.hash_elements, -1);
if (buf_hash_table.ht_table[idx] &&
buf_hash_table.ht_table[idx]->b_hash_next == NULL)
atomic_add_64(&arc.hash_chains, -1);
}
/*
* 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;
kmem_free(buf_hash_table.ht_table,
(buf_hash_table.ht_mask + 1) * sizeof (void *));
for (i = 0; i < BUF_LOCKS; i++)
mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
kmem_cache_destroy(hdr_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);
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;
refcount_destroy(&buf->b_refcnt);
cv_destroy(&buf->b_cv);
}
static int arc_reclaim_needed(void);
void arc_kmem_reclaim(void);
/*
* Reclaim callback -- invoked when memory is low.
*/
/* ARGSUSED */
static void
hdr_recl(void *unused)
{
dprintf("hdr_recl called\n");
if (arc_reclaim_needed())
arc_kmem_reclaim();
}
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;
buf_hash_table.ht_table =
kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
if (buf_hash_table.ht_table == NULL) {
ASSERT(hsize > (1ULL << 8));
hsize >>= 1;
goto retry;
}
hdr_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, NULL, NULL, 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
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)) {
int delta = ab->b_size * ab->b_datacnt;
ASSERT(!MUTEX_HELD(&ab->b_state->mtx));
mutex_enter(&ab->b_state->mtx);
ASSERT(refcount_count(&ab->b_refcnt) > 0);
ASSERT(list_link_active(&ab->b_arc_node));
list_remove(&ab->b_state->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(ab->b_state->lsize, >=, delta);
atomic_add_64(&ab->b_state->lsize, -delta);
mutex_exit(&ab->b_state->mtx);
}
}
static int
remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
{
int cnt;
ASSERT(ab->b_state == arc.anon || MUTEX_HELD(hash_lock));
ASSERT(!GHOST_STATE(ab->b_state));
if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
(ab->b_state != arc.anon)) {
ASSERT(!MUTEX_HELD(&ab->b_state->mtx));
mutex_enter(&ab->b_state->mtx);
ASSERT(!list_link_active(&ab->b_arc_node));
list_insert_head(&ab->b_state->list, ab);
ASSERT(ab->b_datacnt > 0);
atomic_add_64(&ab->b_state->lsize, ab->b_size * ab->b_datacnt);
ASSERT3U(ab->b_state->size, >=, ab->b_state->lsize);
mutex_exit(&ab->b_state->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;
int refcnt = refcount_count(&ab->b_refcnt);
int 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));
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->mtx);
if (use_mutex)
mutex_enter(&old_state->mtx);
ASSERT(list_link_active(&ab->b_arc_node));
list_remove(&old_state->list, ab);
/* ghost elements have a ghost size */
if (GHOST_STATE(old_state)) {
ASSERT(ab->b_datacnt == 0);
ASSERT(ab->b_buf == NULL);
from_delta = ab->b_size;
}
ASSERT3U(old_state->lsize, >=, from_delta);
atomic_add_64(&old_state->lsize, -from_delta);
if (use_mutex)
mutex_exit(&old_state->mtx);
}
if (new_state != arc.anon) {
int use_mutex = !MUTEX_HELD(&new_state->mtx);
if (use_mutex)
mutex_enter(&new_state->mtx);
list_insert_head(&new_state->list, 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(&new_state->lsize, to_delta);
ASSERT3U(new_state->size + to_delta, >=,
new_state->lsize);
if (use_mutex)
mutex_exit(&new_state->mtx);
}
}
ASSERT(!BUF_EMPTY(ab));
if (new_state == arc.anon && old_state != arc.anon) {
buf_hash_remove(ab);
}
/*
* If this buffer isn't being transferred to the MRU-top
* state, it's safe to clear its prefetch flag
*/
if ((new_state != arc.mru) && (new_state != arc.mru_ghost)) {
ab->b_flags &= ~ARC_PREFETCH;
}
/* adjust state sizes */
if (to_delta)
atomic_add_64(&new_state->size, to_delta);
if (from_delta) {
ASSERT3U(old_state->size, >=, from_delta);
atomic_add_64(&old_state->size, -from_delta);
}
ab->b_state = new_state;
}
arc_buf_t *
arc_buf_alloc(spa_t *spa, int size, void *tag)
{
arc_buf_hdr_t *hdr;
arc_buf_t *buf;
ASSERT3U(size, >, 0);
hdr = kmem_cache_alloc(hdr_cache, KM_SLEEP);
ASSERT(BUF_EMPTY(hdr));
hdr->b_size = size;
hdr->b_spa = spa;
hdr->b_state = arc.anon;
hdr->b_arc_access = 0;
buf = kmem_cache_alloc(buf_cache, KM_SLEEP);
buf->b_hdr = hdr;
buf->b_efunc = NULL;
buf->b_private = NULL;
buf->b_next = NULL;
buf->b_data = zio_buf_alloc(size);
hdr->b_buf = buf;
hdr->b_datacnt = 1;
hdr->b_flags = 0;
ASSERT(refcount_is_zero(&hdr->b_refcnt));
(void) refcount_add(&hdr->b_refcnt, tag);
atomic_add_64(&arc.size, size);
atomic_add_64(&arc.anon->size, size);
return (buf);
}
static void *
arc_data_copy(arc_buf_hdr_t *hdr, void *old_data)
{
void *new_data = zio_buf_alloc(hdr->b_size);
atomic_add_64(&arc.size, hdr->b_size);
bcopy(old_data, new_data, hdr->b_size);
atomic_add_64(&hdr->b_state->size, hdr->b_size);
if (list_link_active(&hdr->b_arc_node)) {
ASSERT(refcount_is_zero(&hdr->b_refcnt));
atomic_add_64(&hdr->b_state->lsize, hdr->b_size);
}
return (new_data);
}
void
arc_buf_add_ref(arc_buf_t *buf, void* tag)
{
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
mutex_enter(&arc_eviction_mtx);
hdr = buf->b_hdr;
if (buf->b_data == NULL) {
/*
* This buffer is evicted.
*/
mutex_exit(&arc_eviction_mtx);
return;
} else {
/*
* Prevent this buffer from being evicted
* while we add a reference.
*/
buf->b_hdr = NULL;
}
mutex_exit(&arc_eviction_mtx);
ASSERT(hdr->b_state != arc.anon);
hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
ASSERT(!GHOST_STATE(hdr->b_state));
buf->b_hdr = hdr;
add_reference(hdr, hash_lock, tag);
arc_access_and_exit(hdr, hash_lock);
atomic_add_64(&arc.hits, 1);
}
static void
arc_buf_destroy(arc_buf_t *buf, 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;
zio_buf_free(buf->b_data, size);
atomic_add_64(&arc.size, -size);
if (list_link_active(&buf->b_hdr->b_arc_node)) {
ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
ASSERT(state != arc.anon);
ASSERT3U(state->lsize, >=, size);
atomic_add_64(&state->lsize, -size);
}
ASSERT3U(state->size, >=, size);
atomic_add_64(&state->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;
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)
{
ASSERT(refcount_is_zero(&hdr->b_refcnt));
ASSERT3P(hdr->b_state, ==, arc.anon);
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
if (!BUF_EMPTY(hdr)) {
ASSERT(!HDR_IN_HASH_TABLE(hdr));
bzero(&hdr->b_dva, sizeof (dva_t));
hdr->b_birth = 0;
hdr->b_cksum0 = 0;
}
while (hdr->b_buf) {
arc_buf_t *buf = hdr->b_buf;
if (buf->b_efunc) {
mutex_enter(&arc_eviction_mtx);
ASSERT(buf->b_hdr != NULL);
arc_buf_destroy(hdr->b_buf, FALSE);
hdr->b_buf = buf->b_next;
buf->b_next = arc_eviction_list;
arc_eviction_list = buf;
mutex_exit(&arc_eviction_mtx);
} else {
arc_buf_destroy(hdr->b_buf, TRUE);
}
}
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);
(void) remove_reference(hdr, hash_lock, tag);
if (hdr->b_datacnt > 1)
arc_buf_destroy(buf, TRUE);
else
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) {
ASSERT(HDR_IO_ERROR(hdr));
arc_buf_destroy(buf, 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) {
arc_buf_free(buf, tag);
return (no_callback);
}
mutex_enter(hash_lock);
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, TRUE);
} else if (no_callback) {
ASSERT(hdr->b_buf == buf && buf->b_next == 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.
*/
static uint64_t
arc_evict(arc_state_t *state, int64_t bytes)
{
arc_state_t *evicted_state;
uint64_t bytes_evicted = 0, skipped = 0;
arc_buf_hdr_t *ab, *ab_prev;
kmutex_t *hash_lock;
ASSERT(state == arc.mru || state == arc.mfu);
evicted_state = (state == arc.mru) ? arc.mru_ghost : arc.mfu_ghost;
mutex_enter(&state->mtx);
mutex_enter(&evicted_state->mtx);
for (ab = list_tail(&state->list); ab; ab = ab_prev) {
ab_prev = list_prev(&state->list, ab);
hash_lock = HDR_LOCK(ab);
if (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 (buf->b_data)
bytes_evicted += ab->b_size;
if (buf->b_efunc) {
mutex_enter(&arc_eviction_mtx);
/*
* arc_buf_add_ref() could derail
* this eviction.
*/
if (buf->b_hdr == NULL) {
mutex_exit(&arc_eviction_mtx);
mutex_exit(hash_lock);
goto skip;
}
arc_buf_destroy(buf, FALSE);
ab->b_buf = buf->b_next;
buf->b_next = arc_eviction_list;
arc_eviction_list = buf;
mutex_exit(&arc_eviction_mtx);
} else {
arc_buf_destroy(buf, TRUE);
}
}
ASSERT(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;
DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
mutex_exit(hash_lock);
if (bytes >= 0 && bytes_evicted >= bytes)
break;
} else {
skip:
skipped += 1;
}
}
mutex_exit(&evicted_state->mtx);
mutex_exit(&state->mtx);
if (bytes_evicted < bytes)
dprintf("only evicted %lld bytes from %x",
(longlong_t)bytes_evicted, state);
atomic_add_64(&arc.skipped, skipped);
if (bytes < 0)
return (skipped);
return (bytes_evicted);
}
/*
* 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, int64_t bytes)
{
arc_buf_hdr_t *ab, *ab_prev;
kmutex_t *hash_lock;
uint64_t bytes_deleted = 0;
uint_t bufs_skipped = 0;
ASSERT(GHOST_STATE(state));
top:
mutex_enter(&state->mtx);
for (ab = list_tail(&state->list); ab; ab = ab_prev) {
ab_prev = list_prev(&state->list, ab);
hash_lock = HDR_LOCK(ab);
if (mutex_tryenter(hash_lock)) {
ASSERT(ab->b_buf == NULL);
arc_change_state(arc.anon, ab, hash_lock);
mutex_exit(hash_lock);
atomic_add_64(&arc.deleted, 1);
bytes_deleted += ab->b_size;
arc_hdr_destroy(ab);
DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
if (bytes >= 0 && bytes_deleted >= bytes)
break;
} else {
if (bytes < 0) {
mutex_exit(&state->mtx);
mutex_enter(hash_lock);
mutex_exit(hash_lock);
goto top;
}
bufs_skipped += 1;
}
}
mutex_exit(&state->mtx);
if (bufs_skipped) {
atomic_add_64(&arc.skipped, bufs_skipped);
ASSERT(bytes >= 0);
}
if (bytes_deleted < bytes)
dprintf("only deleted %lld bytes from %p",
(longlong_t)bytes_deleted, state);
}
static void
arc_adjust(void)
{
int64_t top_sz, mru_over, arc_over;
top_sz = arc.anon->size + arc.mru->size;
if (top_sz > arc.p && arc.mru->lsize > 0) {
int64_t toevict = MIN(arc.mru->lsize, top_sz-arc.p);
(void) arc_evict(arc.mru, toevict);
top_sz = arc.anon->size + arc.mru->size;
}
mru_over = top_sz + arc.mru_ghost->size - arc.c;
if (mru_over > 0) {
if (arc.mru_ghost->lsize > 0) {
int64_t todelete = MIN(arc.mru_ghost->lsize, mru_over);
arc_evict_ghost(arc.mru_ghost, todelete);
}
}
if ((arc_over = arc.size - arc.c) > 0) {
int64_t tbl_over;
if (arc.mfu->lsize > 0) {
int64_t toevict = MIN(arc.mfu->lsize, arc_over);
(void) arc_evict(arc.mfu, toevict);
}
tbl_over = arc.size + arc.mru_ghost->lsize +
arc.mfu_ghost->lsize - arc.c*2;
if (tbl_over > 0 && arc.mfu_ghost->lsize > 0) {
int64_t todelete = MIN(arc.mfu_ghost->lsize, tbl_over);
arc_evict_ghost(arc.mfu_ghost, todelete);
}
}
}
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;
buf->b_hdr = NULL;
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);
}
/*
* Flush all *evictable* data from the cache.
* NOTE: this will not touch "active" (i.e. referenced) data.
*/
void
arc_flush(void)
{
while (arc_evict(arc.mru, -1));
while (arc_evict(arc.mfu, -1));
arc_evict_ghost(arc.mru_ghost, -1);
arc_evict_ghost(arc.mfu_ghost, -1);
mutex_enter(&arc_reclaim_thr_lock);
arc_do_user_evicts();
mutex_exit(&arc_reclaim_thr_lock);
ASSERT(arc_eviction_list == NULL);
}
void
arc_kmem_reclaim(void)
{
uint64_t to_free;
/* Remove 12.5% */
/*
* We need arc_reclaim_lock because we don't want multiple
* threads trying to reclaim concurrently.
*/
/*
* umem calls the reclaim func when we destroy the buf cache,
* which is after we do arc_fini(). So we set a flag to prevent
* accessing the destroyed mutexes and lists.
*/
if (arc_dead)
return;
if (arc.c <= arc.c_min)
return;
mutex_enter(&arc_reclaim_lock);
#ifdef _KERNEL
to_free = MAX(arc.c >> 3, ptob(needfree));
#else
to_free = arc.c >> 3;
#endif
if (arc.c > to_free)
atomic_add_64(&arc.c, -to_free);
else
arc.c = arc.c_min;
atomic_add_64(&arc.p, -(arc.p >> 3));
if (arc.c > arc.size)
arc.c = arc.size;
if (arc.c < arc.c_min)
arc.c = arc.c_min;
if (arc.p > arc.c)
arc.p = (arc.c >> 1);
ASSERT((int64_t)arc.p >= 0);
arc_adjust();
mutex_exit(&arc_reclaim_lock);
}
static int
arc_reclaim_needed(void)
{
uint64_t extra;
#ifdef _KERNEL
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 succeeed. 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 caclulation, 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;
extern kmem_cache_t *zio_buf_cache[];
#ifdef _KERNEL
/*
* First purge some DNLC entries, in case the DNLC is using
* up too much memory.
*/
dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
#if defined(__i386)
/*
* Reclaim unused memory from all kmem caches.
*/
kmem_reap();
#endif
#endif
/*
* An agressive reclamation will shrink the cache size as well as
* reap free buffers from the arc kmem caches.
*/
if (strat == ARC_RECLAIM_AGGR)
arc_kmem_reclaim();
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]);
}
}
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;
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 = lbolt + (arc_grow_retry * hz);
arc_kmem_reap_now(last_reclaim);
} else if ((growtime > 0) && ((growtime - lbolt) <= 0)) {
arc.no_grow = FALSE;
}
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(&arc_reclaim_thr_cv,
&arc_reclaim_thr_lock, (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();
}
/*
* 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;
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->size >= arc.mfu_ghost->size) ?
1 : (arc.mfu_ghost->size/arc.mru_ghost->size));
arc.p = MIN(arc.c, arc.p + bytes * mult);
} else if (state == arc.mfu_ghost) {
mult = ((arc.mfu_ghost->size >= arc.mru_ghost->size) ?
1 : (arc.mru_ghost->size/arc.mfu_ghost->size));
arc.p = MAX(0, (int64_t)arc.p - bytes * mult);
}
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()
{
if (arc_reclaim_needed())
return (1);
return (arc.size > arc.c);
}
/*
* The state, supplied as the first argument, is going to have something
* inserted on its behalf. So, determine which cache must be victimized to
* satisfy an insertion for this state. 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_evict_for_state(arc_state_t *state, uint64_t bytes)
{
uint64_t mru_used;
uint64_t mfu_space;
uint64_t evicted;
ASSERT(state == arc.mru || state == arc.mfu);
if (state == arc.mru) {
mru_used = arc.anon->size + arc.mru->size;
if (arc.p > mru_used) {
/* case 1 */
evicted = arc_evict(arc.mfu, bytes);
if (evicted < bytes) {
arc_adjust();
}
} else {
/* case 2 */
evicted = arc_evict(arc.mru, bytes);
if (evicted < bytes) {
arc_adjust();
}
}
} else {
/* MFU case */
mfu_space = arc.c - arc.p;
if (mfu_space > arc.mfu->size) {
/* case 3 */
evicted = arc_evict(arc.mru, bytes);
if (evicted < bytes) {
arc_adjust();
}
} else {
/* case 4 */
evicted = arc_evict(arc.mfu, bytes);
if (evicted < bytes) {
arc_adjust();
}
}
}
}
/*
* This routine is called whenever a buffer is accessed.
* NOTE: the hash lock is dropped in this function.
*/
static void
arc_access_and_exit(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
{
arc_state_t *evict_state = NULL;
int blksz;
ASSERT(MUTEX_HELD(hash_lock));
blksz = buf->b_size;
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.
*/
arc_adapt(blksz, arc.anon);
if (arc_evict_needed())
evict_state = arc.mru;
ASSERT(buf->b_arc_access == 0);
buf->b_arc_access = 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) {
/*
* If this buffer is in the MRU-top state and has the prefetch
* flag, the first read was actually part of a prefetch. In
* this situation, we simply want to clear the flag and return.
* A subsequent access should bump this into the MFU state.
*/
if ((buf->b_flags & ARC_PREFETCH) != 0) {
buf->b_flags &= ~ARC_PREFETCH;
atomic_add_64(&arc.mru->hits, 1);
mutex_exit(hash_lock);
return;
}
/*
* This buffer has been "accessed" only once so far,
* but it is still in the cache. Move it to the MFU
* state.
*/
if (lbolt > 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 = lbolt;
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
arc_change_state(arc.mfu, buf, hash_lock);
}
atomic_add_64(&arc.mru->hits, 1);
} 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;
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);
}
arc_adapt(blksz, arc.mru_ghost);
if (arc_evict_needed())
evict_state = new_state;
buf->b_arc_access = lbolt;
arc_change_state(new_state, buf, hash_lock);
atomic_add_64(&arc.mru_ghost->hits, 1);
} 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: the add_reference() that occurred when we did
* the arc_read() should have kicked this off the list,
* so even if it was a prefetch, it will be put back at
* the head of the list when we remove_reference().
*/
atomic_add_64(&arc.mfu->hits, 1);
} else if (buf->b_state == arc.mfu_ghost) {
/*
* This buffer has been accessed more than once but has
* been evicted from the cache. Move it back to the
* MFU state.
*/
arc_adapt(blksz, arc.mfu_ghost);
if (arc_evict_needed())
evict_state = arc.mfu;
buf->b_arc_access = lbolt;
DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
arc_change_state(arc.mfu, buf, hash_lock);
atomic_add_64(&arc.mfu_ghost->hits, 1);
} else {
ASSERT(!"invalid arc state");
}
mutex_exit(hash_lock);
if (evict_state)
arc_evict_for_state(evict_state, blksz);
}
/* a generic arc_done_func_t which you can use */
/* ARGSUSED */
void
arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
{
bcopy(buf->b_data, arg, buf->b_hdr->b_size);
VERIFY(arc_buf_remove_ref(buf, arg) == 1);
}
/* a generic arc_done_func_t which you can use */
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;
}
}
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(zio->io_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))));
/* byteswap if necessary */
callback_list = hdr->b_acb;
ASSERT(callback_list != NULL);
if (BP_SHOULD_BYTESWAP(zio->io_bp) && callback_list->acb_byteswap)
callback_list->acb_byteswap(buf->b_data, hdr->b_size);
/* 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 = kmem_cache_alloc(buf_cache, KM_SLEEP);
abuf->b_data = arc_data_copy(hdr, buf->b_data);
abuf->b_hdr = hdr;
abuf->b_efunc = NULL;
abuf->b_private = NULL;
abuf->b_next = hdr->b_buf;
hdr->b_buf = abuf;
hdr->b_datacnt += 1;
}
acb->acb_buf = abuf;
abuf = NULL;
} else {
/*
* The caller did not provide a callback function.
* In this case, we should just remove the reference.
*/
if (HDR_FREED_IN_READ(hdr)) {
ASSERT3P(hdr->b_state, ==, arc.anon);
(void) refcount_remove(&hdr->b_refcnt,
acb->acb_private);
} else {
(void) remove_reference(hdr, hash_lock,
acb->acb_private);
}
}
}
hdr->b_acb = NULL;
hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
ASSERT(!HDR_BUF_AVAILABLE(hdr));
if (abuf == buf)
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);
/* translate checksum errors into IO errors */
if (zio->io_error == ECKSUM)
zio->io_error = EIO;
}
/*
* Broadcast before we drop the hash_lock. This is less efficient,
* but avoids 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) {
/*
* 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).
*/
if (zio->io_error == 0 && hdr->b_state == arc.anon)
arc_access_and_exit(hdr, hash_lock);
else
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.
*/
int
arc_read(zio_t *pio, spa_t *spa, blkptr_t *bp, arc_byteswap_func_t *swap,
arc_done_func_t *done, void *private, int priority, int flags,
uint32_t arc_flags, zbookmark_t *zb)
{
arc_buf_hdr_t *hdr;
arc_buf_t *buf;
kmutex_t *hash_lock;
zio_t *rzio;
top:
hdr = buf_hash_find(spa, BP_IDENTITY(bp), bp->blk_birth, &hash_lock);
if (hdr && hdr->b_datacnt > 0) {
if (HDR_IO_IN_PROGRESS(hdr)) {
if ((arc_flags & ARC_NOWAIT) && done) {
arc_callback_t *acb = NULL;
acb = kmem_zalloc(sizeof (arc_callback_t),
KM_SLEEP);
acb->acb_done = done;
acb->acb_private = private;
acb->acb_byteswap = swap;
if (pio != NULL)
acb->acb_zio_dummy = zio_null(pio,
spa, NULL, NULL, 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);
} else if (arc_flags & ARC_WAIT) {
cv_wait(&hdr->b_cv, hash_lock);
mutex_exit(hash_lock);
goto top;
}
mutex_exit(hash_lock);
return (0);
}
ASSERT(hdr->b_state == arc.mru || hdr->b_state == arc.mfu);
if (done) {
/*
* 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)) {
void *data = arc_data_copy(hdr, buf->b_data);
buf = kmem_cache_alloc(buf_cache, KM_SLEEP);
buf->b_hdr = hdr;
buf->b_data = data;
buf->b_efunc = NULL;
buf->b_private = NULL;
buf->b_next = hdr->b_buf;
hdr->b_buf = buf;
hdr->b_datacnt += 1;
} else {
ASSERT(buf->b_efunc == NULL);
hdr->b_flags &= ~ARC_BUF_AVAILABLE;
}
add_reference(hdr, hash_lock, private);
}
DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
arc_access_and_exit(hdr, hash_lock);
atomic_add_64(&arc.hits, 1);
if (done)
done(NULL, buf, private);
} else {
uint64_t size = BP_GET_LSIZE(bp);
arc_callback_t *acb;
if (hdr == NULL) {
/* this block is not in the cache */
arc_buf_hdr_t *exists;
buf = arc_buf_alloc(spa, size, private);
hdr = buf->b_hdr;
hdr->b_dva = *BP_IDENTITY(bp);
hdr->b_birth = bp->blk_birth;
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);
bzero(&hdr->b_dva, sizeof (dva_t));
hdr->b_birth = 0;
hdr->b_cksum0 = 0;
(void) arc_buf_remove_ref(buf, private);
goto top; /* restart the IO request */
}
} else {
/* this block is in the ghost cache */
ASSERT(GHOST_STATE(hdr->b_state));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
add_reference(hdr, hash_lock, private);
ASSERT3U(refcount_count(&hdr->b_refcnt), ==, 1);
ASSERT(hdr->b_buf == NULL);
buf = kmem_cache_alloc(buf_cache, KM_SLEEP);
buf->b_hdr = hdr;
buf->b_efunc = NULL;
buf->b_private = NULL;
buf->b_next = NULL;
hdr->b_buf = buf;
buf->b_data = zio_buf_alloc(hdr->b_size);
atomic_add_64(&arc.size, hdr->b_size);
ASSERT(hdr->b_datacnt == 0);
hdr->b_datacnt = 1;
}
acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
acb->acb_done = done;
acb->acb_private = private;
acb->acb_byteswap = swap;
ASSERT(hdr->b_acb == NULL);
hdr->b_acb = acb;
/*
* If this DVA is part of a prefetch, mark the buf
* header with the prefetch flag
*/
if (arc_flags & ARC_PREFETCH)
hdr->b_flags |= ARC_PREFETCH;
hdr->b_flags |= ARC_IO_IN_PROGRESS;
/*
* If the buffer has been evicted, migrate it to a present state
* before issuing the I/O. Once we drop the hash-table lock,
* the header will be marked as I/O in progress and have an
* attached buffer. At this point, anybody who finds this
* buffer ought to notice that it's legit but has a pending I/O.
*/
if (GHOST_STATE(hdr->b_state))
arc_access_and_exit(hdr, hash_lock);
else
mutex_exit(hash_lock);
ASSERT3U(hdr->b_size, ==, size);
DTRACE_PROBE3(arc__miss, blkptr_t *, bp, uint64_t, size,
zbookmark_t *, zb);
atomic_add_64(&arc.misses, 1);
rzio = zio_read(pio, spa, bp, buf->b_data, size,
arc_read_done, buf, priority, flags, zb);
if (arc_flags & ARC_WAIT)
return (zio_wait(rzio));
ASSERT(arc_flags & ARC_NOWAIT);
zio_nowait(rzio);
}
return (0);
}
/*
* arc_read() variant to support pool traversal. If the block is already
* in the ARC, make a copy of it; otherwise, the caller will do the I/O.
* The idea is that we don't want pool traversal filling up memory, but
* if the ARC already has the data anyway, we shouldn't pay for the I/O.
*/
int
arc_tryread(spa_t *spa, blkptr_t *bp, void *data)
{
arc_buf_hdr_t *hdr;
kmutex_t *hash_mtx;
int rc = 0;
hdr = buf_hash_find(spa, BP_IDENTITY(bp), bp->blk_birth, &hash_mtx);
if (hdr && hdr->b_datacnt > 0 && !HDR_IO_IN_PROGRESS(hdr)) {
arc_buf_t *buf = hdr->b_buf;
ASSERT(buf);
while (buf->b_data == NULL) {
buf = buf->b_next;
ASSERT(buf);
}
bcopy(buf->b_data, data, hdr->b_size);
} else {
rc = ENOENT;
}
if (hash_mtx)
mutex_exit(hash_mtx);
return (rc);
}
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);
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(&arc_eviction_mtx);
hdr = buf->b_hdr;
if (hdr == NULL) {
/*
* We are in arc_do_user_evicts().
* NOTE: We can't be in arc_buf_add_ref() because
* that would violate the interface rules.
*/
ASSERT(buf->b_data == NULL);
mutex_exit(&arc_eviction_mtx);
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;
buf->b_hdr = NULL;
mutex_exit(&arc_eviction_mtx);
VERIFY(copy.b_efunc(©) == 0);
return (1);
} else {
/*
* Prevent a race with arc_evict()
*/
ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
buf->b_hdr = NULL;
}
mutex_exit(&arc_eviction_mtx);
hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
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);
buf->b_hdr = hdr;
arc_buf_destroy(buf, FALSE);
if (hdr->b_datacnt == 0) {
arc_state_t *old_state = hdr->b_state;
arc_state_t *evicted_state;
ASSERT(refcount_is_zero(&hdr->b_refcnt));
evicted_state =
(old_state == arc.mru) ? arc.mru_ghost : arc.mfu_ghost;
mutex_enter(&old_state->mtx);
mutex_enter(&evicted_state->mtx);
arc_change_state(evicted_state, hdr, hash_lock);
ASSERT(HDR_IN_HASH_TABLE(hdr));
hdr->b_flags = ARC_IN_HASH_TABLE;
mutex_exit(&evicted_state->mtx);
mutex_exit(&old_state->mtx);
}
mutex_exit(hash_lock);
VERIFY(buf->b_efunc(buf) == 0);
buf->b_efunc = NULL;
buf->b_private = NULL;
buf->b_hdr = 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
* make a new hdr for the buffer.
*/
void
arc_release(arc_buf_t *buf, void *tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
kmutex_t *hash_lock = HDR_LOCK(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 */
ASSERT3U(refcount_count(&hdr->b_refcnt), ==, 1);
ASSERT(BUF_EMPTY(hdr));
ASSERT(buf->b_efunc == NULL);
return;
}
mutex_enter(hash_lock);
/*
* Do we have more than one buf?
*/
if (hdr->b_buf != buf || buf->b_next != NULL) {
arc_buf_hdr_t *nhdr;
arc_buf_t **bufp;
uint64_t blksz = hdr->b_size;
spa_t *spa = hdr->b_spa;
ASSERT(hdr->b_datacnt > 1);
/*
* Pull the data off of this buf and attach it to
* a new anonymous buf.
*/
(void) remove_reference(hdr, hash_lock, tag);
bufp = &hdr->b_buf;
while (*bufp != buf)
bufp = &(*bufp)->b_next;
*bufp = (*bufp)->b_next;
ASSERT3U(hdr->b_state->size, >=, hdr->b_size);
atomic_add_64(&hdr->b_state->size, -hdr->b_size);
if (refcount_is_zero(&hdr->b_refcnt)) {
ASSERT3U(hdr->b_state->lsize, >=, hdr->b_size);
atomic_add_64(&hdr->b_state->lsize, -hdr->b_size);
}
hdr->b_datacnt -= 1;
mutex_exit(hash_lock);
nhdr = kmem_cache_alloc(hdr_cache, KM_SLEEP);
nhdr->b_size = blksz;
nhdr->b_spa = spa;
nhdr->b_buf = buf;
nhdr->b_state = arc.anon;
nhdr->b_arc_access = 0;
nhdr->b_flags = 0;
nhdr->b_datacnt = 1;
buf->b_hdr = nhdr;
buf->b_next = NULL;
(void) refcount_add(&nhdr->b_refcnt, tag);
atomic_add_64(&arc.anon->size, blksz);
hdr = nhdr;
} else {
ASSERT(refcount_count(&hdr->b_refcnt) == 1);
ASSERT(!list_link_active(&hdr->b_arc_node));
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
arc_change_state(arc.anon, hdr, hash_lock);
hdr->b_arc_access = 0;
mutex_exit(hash_lock);
bzero(&hdr->b_dva, sizeof (dva_t));
hdr->b_birth = 0;
hdr->b_cksum0 = 0;
}
buf->b_efunc = NULL;
buf->b_private = NULL;
}
int
arc_released(arc_buf_t *buf)
{
return (buf->b_data != NULL && buf->b_hdr->b_state == arc.anon);
}
int
arc_has_callback(arc_buf_t *buf)
{
return (buf->b_efunc != NULL);
}
#ifdef ZFS_DEBUG
int
arc_referenced(arc_buf_t *buf)
{
return (refcount_count(&buf->b_hdr->b_refcnt));
}
#endif
static void
arc_write_done(zio_t *zio)
{
arc_buf_t *buf;
arc_buf_hdr_t *hdr;
arc_callback_t *acb;
buf = zio->io_private;
hdr = buf->b_hdr;
acb = hdr->b_acb;
hdr->b_acb = NULL;
ASSERT(acb != NULL);
/* this buffer is on no lists and is not in the hash table */
ASSERT3P(hdr->b_state, ==, arc.anon);
hdr->b_dva = *BP_IDENTITY(zio->io_bp);
hdr->b_birth = zio->io_bp->blk_birth;
hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
/*
* 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-date/checksum. The buffer
* must therefor remain anonymous (and uncached).
*/
if (!BUF_EMPTY(hdr)) {
arc_buf_hdr_t *exists;
kmutex_t *hash_lock;
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().
*/
ASSERT(DVA_EQUAL(BP_IDENTITY(&zio->io_bp_orig),
BP_IDENTITY(zio->io_bp)));
ASSERT3U(zio->io_bp_orig.blk_birth, ==,
zio->io_bp->blk_birth);
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);
}
hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
arc_access_and_exit(hdr, hash_lock);
} else if (acb->acb_done == NULL) {
int destroy_hdr;
/*
* This is an anonymous buffer with no user callback,
* destroy it if there are no active references.
*/
mutex_enter(&arc_eviction_mtx);
destroy_hdr = refcount_is_zero(&hdr->b_refcnt);
hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
mutex_exit(&arc_eviction_mtx);
if (destroy_hdr)
arc_hdr_destroy(hdr);
} else {
hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
}
if (acb->acb_done) {
ASSERT(!refcount_is_zero(&hdr->b_refcnt));
acb->acb_done(zio, buf, acb->acb_private);
}
kmem_free(acb, sizeof (arc_callback_t));
}
int
arc_write(zio_t *pio, spa_t *spa, int checksum, int compress, int ncopies,
uint64_t txg, blkptr_t *bp, arc_buf_t *buf,
arc_done_func_t *done, void *private, int priority, int flags,
uint32_t arc_flags, zbookmark_t *zb)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
arc_callback_t *acb;
zio_t *rzio;
/* this is a private buffer - no locking required */
ASSERT3P(hdr->b_state, ==, arc.anon);
ASSERT(BUF_EMPTY(hdr));
ASSERT(!HDR_IO_ERROR(hdr));
acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
acb->acb_done = done;
acb->acb_private = private;
acb->acb_byteswap = (arc_byteswap_func_t *)-1;
hdr->b_acb = acb;
hdr->b_flags |= ARC_IO_IN_PROGRESS;
rzio = zio_write(pio, spa, checksum, compress, ncopies, txg, bp,
buf->b_data, hdr->b_size, arc_write_done, buf, priority, flags, zb);
if (arc_flags & ARC_WAIT)
return (zio_wait(rzio));
ASSERT(arc_flags & ARC_NOWAIT);
zio_nowait(rzio);
return (0);
}
int
arc_free(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp,
zio_done_func_t *done, void *private, uint32_t arc_flags)
{
arc_buf_hdr_t *ab;
kmutex_t *hash_lock;
zio_t *zio;
/*
* If this buffer is in the cache, release it, so it
* can be re-used.
*/
ab = buf_hash_find(spa, BP_IDENTITY(bp), bp->blk_birth, &hash_lock);
if (ab != NULL) {
/*
* The checksum of blocks to free is not always
* preserved (eg. on the deadlist). However, if it is
* nonzero, it should match what we have in the cache.
*/
ASSERT(bp->blk_cksum.zc_word[0] == 0 ||
ab->b_cksum0 == bp->blk_cksum.zc_word[0]);
if (ab->b_state != arc.anon)
arc_change_state(arc.anon, ab, hash_lock);
if (refcount_is_zero(&ab->b_refcnt)) {
mutex_exit(hash_lock);
arc_hdr_destroy(ab);
atomic_add_64(&arc.deleted, 1);
} else {
/*
* We could have an outstanding read on this
* block, so multiple active references are
* possible. But we should only have a single
* data buffer associated at this point.
*/
ASSERT3U(ab->b_datacnt, ==, 1);
if (HDR_IO_IN_PROGRESS(ab))
ab->b_flags |= ARC_FREED_IN_READ;
if (HDR_IN_HASH_TABLE(ab))
buf_hash_remove(ab);
ab->b_arc_access = 0;
bzero(&ab->b_dva, sizeof (dva_t));
ab->b_birth = 0;
ab->b_cksum0 = 0;
ab->b_buf->b_efunc = NULL;
ab->b_buf->b_private = NULL;
mutex_exit(hash_lock);
}
}
zio = zio_free(pio, spa, txg, bp, done, private);
if (arc_flags & ARC_WAIT)
return (zio_wait(zio));
ASSERT(arc_flags & ARC_NOWAIT);
zio_nowait(zio);
return (0);
}
void
arc_tempreserve_clear(uint64_t tempreserve)
{
atomic_add_64(&arc_tempreserve, -tempreserve);
ASSERT((int64_t)arc_tempreserve >= 0);
}
int
arc_tempreserve_space(uint64_t tempreserve)
{
#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 (tempreserve > arc.c/4 && !arc.no_grow)
arc.c = MIN(arc.c_max, tempreserve * 4);
if (tempreserve > arc.c)
return (ENOMEM);
/*
* 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.
*
* XXX The limit should be adjusted dynamically to keep the time
* to sync a dataset fixed (around 1-5 seconds?).
*/
if (tempreserve + arc_tempreserve + arc.anon->size > arc.c / 2 &&
arc_tempreserve + arc.anon->size > arc.c / 4) {
dprintf("failing, arc_tempreserve=%lluK anon=%lluK "
"tempreserve=%lluK arc.c=%lluK\n",
arc_tempreserve>>10, arc.anon->lsize>>10,
tempreserve>>10, arc.c>>10);
return (ERESTART);
}
atomic_add_64(&arc_tempreserve, tempreserve);
return (0);
}
void
arc_init(void)
{
mutex_init(&arc_reclaim_lock, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
/* 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);
#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 3/4 of all memory, or all but 1GB, whichever is more */
if (arc.c * 8 >= 1<<30)
arc.c_max = (arc.c * 8) - (1<<30);
else
arc.c_max = arc.c_min;
arc.c_max = MAX(arc.c * 6, arc.c_max);
arc.c = arc.c_max;
arc.p = (arc.c >> 1);
/* 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.size = 0;
list_create(&arc.mru->list, sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc.mru_ghost->list, sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc.mfu->list, sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_arc_node));
list_create(&arc.mfu_ghost->list, sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_arc_node));
buf_init();
arc_thread_exit = 0;
arc_eviction_list = NULL;
mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
(void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
TS_RUN, minclsyspri);
}
void
arc_fini(void)
{
mutex_enter(&arc_reclaim_thr_lock);
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();
arc_dead = TRUE;
mutex_destroy(&arc_eviction_mtx);
mutex_destroy(&arc_reclaim_lock);
mutex_destroy(&arc_reclaim_thr_lock);
cv_destroy(&arc_reclaim_thr_cv);
list_destroy(&arc.mru->list);
list_destroy(&arc.mru_ghost->list);
list_destroy(&arc.mfu->list);
list_destroy(&arc.mfu_ghost->list);
buf_fini();
}