/* * 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 and algorithms used here * are 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. * * Note that the majority of the performance stats are manipulated * with atomic operations. */ #include #include #include #include #include #ifdef _KERNEL #include #include #include #include #endif #include 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_top - recently used, currently cached * ARC_mru_bot - recentely used, no longer in cache * ARC_mfu_top - frequently used, currently cached * ARC_mfu_bot - 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_top * that cannot be freed. Generally, they will aquire a DVA * as they are written and migrate onto the arc_mru_top 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_top; static arc_state_t ARC_mru_bot; static arc_state_t ARC_mfu_top; static arc_state_t ARC_mfu_bot; static struct arc { arc_state_t *anon; arc_state_t *mru_top; arc_state_t *mru_bot; arc_state_t *mfu_top; arc_state_t *mfu_bot; uint64_t size; /* Actual total arc size */ uint64_t p; /* Target size (in bytes) of mru_top */ 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 */ uint64_t incr; /* Size by which to increment arc.c */ int64_t size_check; /* 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; /* Default amount to grow arc.incr */ static int64_t arc_incr_size = 1024; /* > 0 ==> time to increment arc.c */ static int64_t arc_size_check_default = -1000; 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; 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; }; /* * 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_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 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) /* * 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; 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; /* 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))); 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; /* 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); } void arc_kmem_reclaim(void); /* * Reclaim callback -- invoked when memory is low. */ /* ARGSUSED */ static void hdr_recl(void *unused) { dprintf("hdr_recl called\n"); arc_kmem_reclaim(); } static void buf_init(void) { uint64_t *ct; uint64_t hsize = 1ULL << 10; int i, j; /* * The hash table is big enough to fill all of physical memory * with an average 4k block size. The table will take up * totalmem*sizeof(void*)/4k bytes (eg. 2MB/GB with 8-byte * pointers). */ while (hsize * 4096 < physmem * PAGESIZE) hsize <<= 1; buf_hash_table.ht_mask = hsize - 1; buf_hash_table.ht_table = kmem_zalloc(hsize * sizeof (void*), KM_SLEEP); 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 */ #define ARC_TAG (void *)0x05201962 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)) { ASSERT(!MUTEX_HELD(&ab->b_state->mtx)); mutex_enter(&ab->b_state->mtx); ASSERT(!refcount_is_zero(&ab->b_refcnt)); ASSERT(list_link_active(&ab->b_arc_node)); list_remove(&ab->b_state->list, ab); ASSERT3U(ab->b_state->lsize, >=, ab->b_size); ab->b_state->lsize -= ab->b_size; mutex_exit(&ab->b_state->mtx); } } static int remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag) { int cnt; ASSERT(MUTEX_HELD(hash_lock)); 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_buf != NULL); ab->b_state->lsize += ab->b_size; 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_buf_t *buf; ASSERT(MUTEX_HELD(hash_lock)); /* * If this buffer is evictable, transfer it from the * old state list to the new state list. */ if (refcount_is_zero(&ab->b_refcnt)) { if (ab->b_state != arc.anon) { int drop_mutex = FALSE; if (!MUTEX_HELD(&ab->b_state->mtx)) { mutex_enter(&ab->b_state->mtx); drop_mutex = TRUE; } ASSERT(list_link_active(&ab->b_arc_node)); list_remove(&ab->b_state->list, ab); ASSERT3U(ab->b_state->lsize, >=, ab->b_size); ab->b_state->lsize -= ab->b_size; if (drop_mutex) mutex_exit(&ab->b_state->mtx); } if (new_state != arc.anon) { int drop_mutex = FALSE; if (!MUTEX_HELD(&new_state->mtx)) { mutex_enter(&new_state->mtx); drop_mutex = TRUE; } list_insert_head(&new_state->list, ab); ASSERT(ab->b_buf != NULL); new_state->lsize += ab->b_size; if (drop_mutex) mutex_exit(&new_state->mtx); } } ASSERT(!BUF_EMPTY(ab)); if (new_state == arc.anon && ab->b_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_top) && (new_state != arc.mru_bot)) { ab->b_flags &= ~ARC_PREFETCH; } buf = ab->b_buf; if (buf == NULL) { ASSERT3U(ab->b_state->size, >=, ab->b_size); atomic_add_64(&ab->b_state->size, -ab->b_size); /* we should only be here if we are deleting state */ ASSERT(new_state == arc.anon && (ab->b_state == arc.mru_bot || ab->b_state == arc.mfu_bot)); } else while (buf) { ASSERT3U(ab->b_state->size, >=, ab->b_size); atomic_add_64(&ab->b_state->size, -ab->b_size); atomic_add_64(&new_state->size, ab->b_size); buf = buf->b_next; } 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_next = NULL; buf->b_data = zio_buf_alloc(size); hdr->b_buf = buf; 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_hdr_free(arc_buf_hdr_t *hdr) { ASSERT(refcount_is_zero(&hdr->b_refcnt)); ASSERT3P(hdr->b_state, ==, arc.anon); if (!BUF_EMPTY(hdr)) { /* * We can be called with an arc state lock held, * so we can't hold a hash lock here. * ASSERT(not in hash table) */ ASSERT(!HDR_IO_IN_PROGRESS(hdr)); bzero(&hdr->b_dva, sizeof (dva_t)); hdr->b_birth = 0; hdr->b_cksum0 = 0; } if (hdr->b_buf) { arc_buf_t *buf = hdr->b_buf; ASSERT3U(hdr->b_size, >, 0); zio_buf_free(buf->b_data, hdr->b_size); atomic_add_64(&arc.size, -hdr->b_size); ASSERT3U(arc.anon->size, >=, hdr->b_size); atomic_add_64(&arc.anon->size, -hdr->b_size); ASSERT3P(buf->b_next, ==, NULL); kmem_cache_free(buf_cache, buf); hdr->b_buf = 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; kmutex_t *hash_lock = HDR_LOCK(hdr); int freeable; mutex_enter(hash_lock); if (remove_reference(hdr, hash_lock, tag) > 0) { arc_buf_t **bufp = &hdr->b_buf; arc_state_t *state = hdr->b_state; uint64_t size = hdr->b_size; ASSERT(hdr->b_state != arc.anon || HDR_IO_ERROR(hdr)); while (*bufp != buf) { ASSERT(*bufp); bufp = &(*bufp)->b_next; } *bufp = buf->b_next; mutex_exit(hash_lock); zio_buf_free(buf->b_data, size); atomic_add_64(&arc.size, -size); kmem_cache_free(buf_cache, buf); ASSERT3U(state->size, >=, size); atomic_add_64(&state->size, -size); return; } /* don't free buffers that are in the middle of an async write */ freeable = (hdr->b_state == arc.anon && hdr->b_acb == NULL); mutex_exit(hash_lock); if (freeable) arc_hdr_free(hdr); } 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_state(arc_state_t *state, int64_t bytes) { arc_state_t *evicted_state; uint64_t bytes_evicted = 0; arc_buf_hdr_t *ab, *ab_prev; kmutex_t *hash_lock; ASSERT(state == arc.mru_top || state == arc.mfu_top); if (state == arc.mru_top) evicted_state = arc.mru_bot; else evicted_state = arc.mfu_bot; 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); arc_change_state(evicted_state, ab, hash_lock); zio_buf_free(ab->b_buf->b_data, ab->b_size); atomic_add_64(&arc.size, -ab->b_size); ASSERT3P(ab->b_buf->b_next, ==, NULL); kmem_cache_free(buf_cache, ab->b_buf); ab->b_buf = NULL; DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab); bytes_evicted += ab->b_size; mutex_exit(hash_lock); if (bytes_evicted >= bytes) break; } else { atomic_add_64(&arc.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); 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_delete_state(arc_state_t *state, int64_t bytes) { uint_t bufs_skipped = 0; uint64_t bytes_deleted = 0; arc_buf_hdr_t *ab, *ab_prev; kmutex_t *hash_lock; 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)) { arc_change_state(arc.anon, ab, hash_lock); mutex_exit(hash_lock); atomic_add_64(&arc.deleted, 1); DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab); bytes_deleted += ab->b_size; arc_hdr_free(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_top->size; if (top_sz > arc.p && arc.mru_top->lsize > 0) { int64_t toevict = MIN(arc.mru_top->lsize, top_sz-arc.p); (void) arc_evict_state(arc.mru_top, toevict); top_sz = arc.anon->size + arc.mru_top->size; } mru_over = top_sz + arc.mru_bot->size - arc.c; if (mru_over > 0) { if (arc.mru_bot->lsize > 0) { int64_t todelete = MIN(arc.mru_bot->lsize, mru_over); arc_delete_state(arc.mru_bot, todelete); } } if ((arc_over = arc.size - arc.c) > 0) { int64_t table_over; if (arc.mfu_top->lsize > 0) { int64_t toevict = MIN(arc.mfu_top->lsize, arc_over); (void) arc_evict_state(arc.mfu_top, toevict); } table_over = arc.size + arc.mru_bot->lsize + arc.mfu_bot->lsize - arc.c*2; if (table_over > 0 && arc.mfu_bot->lsize > 0) { int64_t todelete = MIN(arc.mfu_bot->lsize, table_over); arc_delete_state(arc.mfu_bot, todelete); } } } /* * Flush all *evictable* data from the cache. * NOTE: this will not touch "active" (i.e. referenced) data. */ void arc_flush(void) { arc_delete_state(arc.mru_top, -1); arc_delete_state(arc.mfu_top, -1); arc_delete_state(arc.mru_bot, -1); arc_delete_state(arc.mfu_bot, -1); } void arc_kmem_reclaim(void) { /* Remove 6.25% */ /* * 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; mutex_enter(&arc_reclaim_lock); atomic_add_64(&arc.c, -(arc.c >> 4)); if (arc.c < arc.c_min) arc.c = arc.c_min; atomic_add_64(&arc.p, -(arc.p >> 4)); arc_adjust(); /* Cool it for a while */ arc.incr = 0; arc.size_check = arc_size_check_default << 3; mutex_exit(&arc_reclaim_lock); } static int arc_reclaim_needed(void) { uint64_t extra; #ifdef _KERNEL /* * 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 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 defined(__i386) 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 *)arc_reduce_dnlc_percent); #endif /* * an agressive reclamation will shrink the cache size as well as reap * free kmem buffers. The arc_kmem_reclaim function is called when the * header-cache is reaped, so we only reap the header cache if we're * performing an agressive reclaim. If we're not, just clean the kmem * buffer caches. */ if (strat == ARC_RECLAIM_AGGR) kmem_cache_reap_now(hdr_cache); kmem_cache_reap_now(buf_cache); 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]); } } } 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; } /* 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(); } static void arc_try_grow(int64_t bytes) { /* * If we're within (2 * maxblocksize) bytes of the target * cache size, increment the target cache size */ atomic_add_64((uint64_t *)&arc.size_check, 1); if (arc_reclaim_needed()) { cv_signal(&arc_reclaim_thr_cv); return; } if (arc.no_grow) return; /* * return true if we successfully grow, or if there's enough space that * we don't have to grow. Above, we return false if we can't grow, or * if we shouldn't because a reclaim is in progress. */ if ((arc.c - arc.size) <= (2ULL << SPA_MAXBLOCKSHIFT)) { if (arc.size_check > 0) { arc.size_check = arc_size_check_default; atomic_add_64(&arc.incr, arc_incr_size); } atomic_add_64(&arc.c, MIN(bytes, arc.incr)); if (arc.c > arc.c_max) arc.c = arc.c_max; else atomic_add_64(&arc.p, MIN(bytes, arc.incr)); } else if (arc.size > arc.c) { if (arc.size_check > 0) { arc.size_check = arc_size_check_default; atomic_add_64(&arc.incr, arc_incr_size); } atomic_add_64(&arc.c, MIN(bytes, arc.incr)); if (arc.c > arc.c_max) arc.c = arc.c_max; else atomic_add_64(&arc.p, MIN(bytes, arc.incr)); } } /* * check if the cache has reached its limits and eviction is required prior to * insert. In this situation, we want to evict if no_grow is set Otherwise, the * cache is either big enough that we can insert, or a arc_try_grow will result * in more space being made available. */ static int arc_evict_needed() { if (arc_reclaim_needed()) return (1); if (arc.no_grow || (arc.c > arc.c_max) || (arc.size > arc.c)) return (1); return (0); } /* * 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_top) -> * 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_top) -> * 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_top) -> * 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_top) -> * 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_top || state == arc.mfu_top); if (state == arc.mru_top) { mru_used = arc.anon->size + arc.mru_top->size; if (arc.p > mru_used) { /* case 1 */ evicted = arc_evict_state(arc.mfu_top, bytes); if (evicted < bytes) { arc_adjust(); } } else { /* case 2 */ evicted = arc_evict_state(arc.mru_top, bytes); if (evicted < bytes) { arc_adjust(); } } } else { /* MFU_top case */ mfu_space = arc.c - arc.p; if (mfu_space > arc.mfu_top->size) { /* case 3 */ evicted = arc_evict_state(arc.mru_top, bytes); if (evicted < bytes) { arc_adjust(); } } else { /* case 4 */ evicted = arc_evict_state(arc.mfu_top, bytes); if (evicted < bytes) { arc_adjust(); } } } } /* * This routine is called whenever a buffer is accessed. */ static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock) { int blksz, mult; 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_try_grow(blksz); if (arc_evict_needed()) { arc_evict_for_state(arc.mru_top, blksz); } ASSERT(buf->b_arc_access == 0); buf->b_arc_access = lbolt; DTRACE_PROBE1(new_state__mru_top, arc_buf_hdr_t *, buf); arc_change_state(arc.mru_top, buf, hash_lock); /* * If we are using less than 2/3 of our total target * cache size, bump up the target size for the MRU * list. */ if (arc.size < arc.c*2/3) { arc.p = arc.anon->size + arc.mru_top->size + arc.c/6; } } else if (buf->b_state == arc.mru_top) { /* * 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_top->hits, 1); 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_top, arc_buf_hdr_t *, buf); arc_change_state(arc.mfu_top, buf, hash_lock); } atomic_add_64(&arc.mru_top->hits, 1); } else if (buf->b_state == arc.mru_bot) { 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_top; DTRACE_PROBE1(new_state__mru_top, arc_buf_hdr_t *, buf); } else { new_state = arc.mfu_top; DTRACE_PROBE1(new_state__mfu_top, arc_buf_hdr_t *, buf); } arc_try_grow(blksz); if (arc_evict_needed()) { arc_evict_for_state(new_state, blksz); } /* Bump up the target size of the MRU list */ mult = ((arc.mru_bot->size >= arc.mfu_bot->size) ? 1 : (arc.mfu_bot->size/arc.mru_bot->size)); arc.p = MIN(arc.c, arc.p + blksz * mult); buf->b_arc_access = lbolt; arc_change_state(new_state, buf, hash_lock); atomic_add_64(&arc.mru_bot->hits, 1); } else if (buf->b_state == arc.mfu_top) { /* * 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_top->hits, 1); } else if (buf->b_state == arc.mfu_bot) { /* * This buffer has been accessed more than once but has * been evicted from the cache. Move it back to the * MFU state. */ arc_try_grow(blksz); if (arc_evict_needed()) { arc_evict_for_state(arc.mfu_top, blksz); } /* Bump up the target size for the MFU list */ mult = ((arc.mfu_bot->size >= arc.mru_bot->size) ? 1 : (arc.mru_bot->size/arc.mfu_bot->size)); arc.p = MAX(0, (int64_t)arc.p - blksz * mult); buf->b_arc_access = lbolt; DTRACE_PROBE1(new_state__mfu_top, arc_buf_hdr_t *, buf); arc_change_state(arc.mfu_top, buf, hash_lock); atomic_add_64(&arc.mfu_bot->hits, 1); } 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) { bcopy(buf->b_data, arg, buf->b_hdr->b_size); arc_buf_free(buf, arg); } /* 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) { arc_buf_free(buf, arg); *bufp = NULL; } else { *bufp = buf; } } static void arc_read_done(zio_t *zio) { arc_buf_hdr_t *hdr; 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; if (!HDR_FREED_IN_READ(hdr)) { arc_buf_hdr_t *found; found = buf_hash_find(zio->io_spa, &hdr->b_dva, hdr->b_birth, &hash_lock); /* * Buffer 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. */ ASSERT(found); ASSERT(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 = zio_buf_alloc(hdr->b_size); atomic_add_64(&arc.size, hdr->b_size); bcopy(buf->b_data, abuf->b_data, hdr->b_size); abuf->b_hdr = hdr; abuf->b_next = hdr->b_buf; hdr->b_buf = abuf; atomic_add_64(&hdr->b_state->size, hdr->b_size); } 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(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); freeable = refcount_is_zero(&hdr->b_refcnt); } if (!HDR_FREED_IN_READ(hdr)) { /* * 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(hdr, 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); } cv_broadcast(&hdr->b_cv); /* 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_free(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) { 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_buf) { ASSERT((hdr->b_state == arc.mru_top) || (hdr->b_state == arc.mfu_top) || ((hdr->b_state == arc.anon) && (HDR_IO_IN_PROGRESS(hdr)))); 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); } /* * If there is already a reference on this block, create * a new copy of the data so that we will be guaranteed * that arc_release() will always succeed. */ if (done) add_reference(hdr, hash_lock, private); if (done && refcount_count(&hdr->b_refcnt) > 1) { buf = kmem_cache_alloc(buf_cache, KM_SLEEP); buf->b_data = zio_buf_alloc(hdr->b_size); ASSERT3U(refcount_count(&hdr->b_refcnt), >, 1); atomic_add_64(&arc.size, hdr->b_size); bcopy(hdr->b_buf->b_data, buf->b_data, hdr->b_size); buf->b_hdr = hdr; buf->b_next = hdr->b_buf; hdr->b_buf = buf; atomic_add_64(&hdr->b_state->size, hdr->b_size); } else { buf = hdr->b_buf; } DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); arc_access(hdr, hash_lock); mutex_exit(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; arc_buf_free(buf, private); goto top; /* restart the IO request */ } } else { /* this block is in the ghost cache */ ASSERT((hdr->b_state == arc.mru_bot) || (hdr->b_state == arc.mfu_bot)); add_reference(hdr, hash_lock, private); buf = kmem_cache_alloc(buf_cache, KM_SLEEP); buf->b_data = zio_buf_alloc(hdr->b_size); atomic_add_64(&arc.size, hdr->b_size); ASSERT(!HDR_IO_IN_PROGRESS(hdr)); ASSERT3U(refcount_count(&hdr->b_refcnt), ==, 1); buf->b_hdr = hdr; buf->b_next = NULL; hdr->b_buf = buf; } 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 ((hdr->b_state == arc.mru_bot) || (hdr->b_state == arc.mfu_bot)) arc_access(hdr, hash_lock); mutex_exit(hash_lock); ASSERT3U(hdr->b_size, ==, size); DTRACE_PROBE2(arc__miss, blkptr_t *, bp, uint64_t, size); atomic_add_64(&arc.misses, 1); rzio = zio_read(pio, spa, bp, buf->b_data, size, arc_read_done, buf, priority, flags); 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_buf && !HDR_IO_IN_PROGRESS(hdr)) bcopy(hdr->b_buf->b_data, data, hdr->b_size); else rc = ENOENT; if (hash_mtx) mutex_exit(hash_mtx); return (rc); } /* * 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)); return; } mutex_enter(hash_lock); if (refcount_count(&hdr->b_refcnt) > 1) { arc_buf_hdr_t *nhdr; arc_buf_t **bufp; uint64_t blksz = hdr->b_size; spa_t *spa = hdr->b_spa; /* * Pull the data off of this buf and attach it to * a new anonymous buf. */ bufp = &hdr->b_buf; while (*bufp != buf) { ASSERT(*bufp); bufp = &(*bufp)->b_next; } *bufp = (*bufp)->b_next; (void) refcount_remove(&hdr->b_refcnt, tag); ASSERT3U(hdr->b_state->size, >=, hdr->b_size); atomic_add_64(&hdr->b_state->size, -hdr->b_size); 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; 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(!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; } } int arc_released(arc_buf_t *buf) { return (buf->b_hdr->b_state == arc.anon); } 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; /* 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]; /* clear the "in-write" flag */ hdr->b_hash_next = NULL; /* This write may be all-zero */ 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_free(exists); exists = buf_hash_insert(hdr, &hash_lock); ASSERT3P(exists, ==, NULL); } arc_access(hdr, hash_lock); mutex_exit(hash_lock); } if (acb && acb->acb_done) { ASSERT(!refcount_is_zero(&hdr->b_refcnt)); acb->acb_done(zio, buf, acb->acb_private); } if (acb) kmem_free(acb, sizeof (arc_callback_t)); } int arc_write(zio_t *pio, spa_t *spa, int checksum, int compress, 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) { 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; rzio = zio_write(pio, spa, checksum, compress, txg, bp, buf->b_data, hdr->b_size, arc_write_done, buf, priority, flags); 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]); arc_change_state(arc.anon, ab, hash_lock); if (refcount_is_zero(&ab->b_refcnt)) { mutex_exit(hash_lock); arc_hdr_free(ab); atomic_add_64(&arc.deleted, 1); } else { ASSERT3U(refcount_count(&ab->b_refcnt), ==, 1); if (HDR_IO_IN_PROGRESS(ab)) ab->b_flags |= ARC_FREED_IN_READ; ab->b_arc_access = 0; bzero(&ab->b_dva, sizeof (dva_t)); ab->b_birth = 0; ab->b_cksum0 = 0; 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_top = &ARC_mru_top; arc.mru_bot = &ARC_mru_bot; arc.mfu_top = &ARC_mfu_top; arc.mfu_bot = &ARC_mfu_bot; list_create(&arc.mru_top->list, sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); list_create(&arc.mru_bot->list, sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); list_create(&arc.mfu_top->list, sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); list_create(&arc.mfu_bot->list, sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node)); buf_init(); arc_thread_exit = 0; (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_reclaim_lock); mutex_destroy(&arc_reclaim_thr_lock); cv_destroy(&arc_reclaim_thr_cv); list_destroy(&arc.mru_top->list); list_destroy(&arc.mru_bot->list); list_destroy(&arc.mfu_top->list); list_destroy(&arc.mfu_bot->list); buf_fini(); }