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+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ */
+
+/*
+ * DVA-based Adjustable Replacement Cache
+ *
+ * While much of the theory of operation used here is
+ * based on the self-tuning, low overhead replacement cache
+ * presented by Megiddo and Modha at FAST 2003, there are some
+ * significant differences:
+ *
+ * 1. The Megiddo and Modha model assumes any page is evictable.
+ * Pages in its cache cannot be "locked" into memory. This makes
+ * the eviction algorithm simple: evict the last page in the list.
+ * This also make the performance characteristics easy to reason
+ * about. Our cache is not so simple. At any given moment, some
+ * subset of the blocks in the cache are un-evictable because we
+ * have handed out a reference to them. Blocks are only evictable
+ * when there are no external references active. This makes
+ * eviction far more problematic: we choose to evict the evictable
+ * blocks that are the "lowest" in the list.
+ *
+ * There are times when it is not possible to evict the requested
+ * space. In these circumstances we are unable to adjust the cache
+ * size. To prevent the cache growing unbounded at these times we
+ * implement a "cache throttle" that slows the flow of new data
+ * into the cache until we can make space available.
+ *
+ * 2. The Megiddo and Modha model assumes a fixed cache size.
+ * Pages are evicted when the cache is full and there is a cache
+ * miss. Our model has a variable sized cache. It grows with
+ * high use, but also tries to react to memory pressure from the
+ * operating system: decreasing its size when system memory is
+ * tight.
+ *
+ * 3. The Megiddo and Modha model assumes a fixed page size. All
+ * elements of the cache are therefor exactly the same size. So
+ * when adjusting the cache size following a cache miss, its simply
+ * a matter of choosing a single page to evict. In our model, we
+ * have variable sized cache blocks (rangeing from 512 bytes to
+ * 128K bytes). We therefor choose a set of blocks to evict to make
+ * space for a cache miss that approximates as closely as possible
+ * the space used by the new block.
+ *
+ * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
+ * by N. Megiddo & D. Modha, FAST 2003
+ */
+
+/*
+ * The locking model:
+ *
+ * A new reference to a cache buffer can be obtained in two
+ * ways: 1) via a hash table lookup using the DVA as a key,
+ * or 2) via one of the ARC lists. The arc_read() interface
+ * uses method 1, while the internal arc algorithms for
+ * adjusting the cache use method 2. We therefor provide two
+ * types of locks: 1) the hash table lock array, and 2) the
+ * arc list locks.
+ *
+ * Buffers do not have their own mutexs, rather they rely on the
+ * hash table mutexs for the bulk of their protection (i.e. most
+ * fields in the arc_buf_hdr_t are protected by these mutexs).
+ *
+ * buf_hash_find() returns the appropriate mutex (held) when it
+ * locates the requested buffer in the hash table. It returns
+ * NULL for the mutex if the buffer was not in the table.
+ *
+ * buf_hash_remove() expects the appropriate hash mutex to be
+ * already held before it is invoked.
+ *
+ * Each arc state also has a mutex which is used to protect the
+ * buffer list associated with the state. When attempting to
+ * obtain a hash table lock while holding an arc list lock you
+ * must use: mutex_tryenter() to avoid deadlock. Also note that
+ * the active state mutex must be held before the ghost state mutex.
+ *
+ * Arc buffers may have an associated eviction callback function.
+ * This function will be invoked prior to removing the buffer (e.g.
+ * in arc_do_user_evicts()). Note however that the data associated
+ * with the buffer may be evicted prior to the callback. The callback
+ * must be made with *no locks held* (to prevent deadlock). Additionally,
+ * the users of callbacks must ensure that their private data is
+ * protected from simultaneous callbacks from arc_buf_evict()
+ * and arc_do_user_evicts().
+ *
+ * Note that the majority of the performance stats are manipulated
+ * with atomic operations.
+ *
+ * The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
+ *
+ * - L2ARC buflist creation
+ * - L2ARC buflist eviction
+ * - L2ARC write completion, which walks L2ARC buflists
+ * - ARC header destruction, as it removes from L2ARC buflists
+ * - ARC header release, as it removes from L2ARC buflists
+ */
+
+#include <sys/spa.h>
+#include <sys/zio.h>
+#include <sys/zfs_context.h>
+#include <sys/arc.h>
+#include <sys/refcount.h>
+#include <sys/vdev.h>
+#include <sys/vdev_impl.h>
+#ifdef _KERNEL
+#include <sys/vmsystm.h>
+#include <vm/anon.h>
+#include <sys/fs/swapnode.h>
+#include <sys/dnlc.h>
+#endif
+#include <sys/callb.h>
+#include <sys/kstat.h>
+#include <zfs_fletcher.h>
+
+static kmutex_t arc_reclaim_thr_lock;
+static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
+static uint8_t arc_thread_exit;
+
+extern int zfs_write_limit_shift;
+extern uint64_t zfs_write_limit_max;
+extern kmutex_t zfs_write_limit_lock;
+
+#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;
+
+/* shift of arc_c for calculating both min and max arc_p */
+static int arc_p_min_shift = 4;
+
+/* log2(fraction of arc to reclaim) */
+static int arc_shrink_shift = 5;
+
+/*
+ * minimum lifespan of a prefetch block in clock ticks
+ * (initialized in arc_init())
+ */
+static int arc_min_prefetch_lifespan;
+
+static int arc_dead;
+
+/*
+ * The arc has filled available memory and has now warmed up.
+ */
+static boolean_t arc_warm;
+
+/*
+ * These tunables are for performance analysis.
+ */
+uint64_t zfs_arc_max;
+uint64_t zfs_arc_min;
+uint64_t zfs_arc_meta_limit = 0;
+int zfs_arc_grow_retry = 0;
+int zfs_arc_shrink_shift = 0;
+int zfs_arc_p_min_shift = 0;
+
+/*
+ * Note that buffers can be in one of 6 states:
+ * ARC_anon - anonymous (discussed below)
+ * ARC_mru - recently used, currently cached
+ * ARC_mru_ghost - recentely used, no longer in cache
+ * ARC_mfu - frequently used, currently cached
+ * ARC_mfu_ghost - frequently used, no longer in cache
+ * ARC_l2c_only - exists in L2ARC but not other states
+ * When there are no active references to the buffer, they are
+ * are linked onto a list in one of these arc states. These are
+ * the only buffers that can be evicted or deleted. Within each
+ * state there are multiple lists, one for meta-data and one for
+ * non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
+ * etc.) is tracked separately so that it can be managed more
+ * explicitly: favored over data, limited explicitly.
+ *
+ * Anonymous buffers are buffers that are not associated with
+ * a DVA. These are buffers that hold dirty block copies
+ * before they are written to stable storage. By definition,
+ * they are "ref'd" and are considered part of arc_mru
+ * that cannot be freed. Generally, they will aquire a DVA
+ * as they are written and migrate onto the arc_mru list.
+ *
+ * The ARC_l2c_only state is for buffers that are in the second
+ * level ARC but no longer in any of the ARC_m* lists. The second
+ * level ARC itself may also contain buffers that are in any of
+ * the ARC_m* states - meaning that a buffer can exist in two
+ * places. The reason for the ARC_l2c_only state is to keep the
+ * buffer header in the hash table, so that reads that hit the
+ * second level ARC benefit from these fast lookups.
+ */
+
+typedef struct arc_state {
+ list_t arcs_list[ARC_BUFC_NUMTYPES]; /* list of evictable buffers */
+ uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
+ uint64_t arcs_size; /* total amount of data in this state */
+ kmutex_t arcs_mtx;
+} arc_state_t;
+
+/* The 6 states: */
+static arc_state_t ARC_anon;
+static arc_state_t ARC_mru;
+static arc_state_t ARC_mru_ghost;
+static arc_state_t ARC_mfu;
+static arc_state_t ARC_mfu_ghost;
+static arc_state_t ARC_l2c_only;
+
+typedef struct arc_stats {
+ kstat_named_t arcstat_hits;
+ kstat_named_t arcstat_misses;
+ kstat_named_t arcstat_demand_data_hits;
+ kstat_named_t arcstat_demand_data_misses;
+ kstat_named_t arcstat_demand_metadata_hits;
+ kstat_named_t arcstat_demand_metadata_misses;
+ kstat_named_t arcstat_prefetch_data_hits;
+ kstat_named_t arcstat_prefetch_data_misses;
+ kstat_named_t arcstat_prefetch_metadata_hits;
+ kstat_named_t arcstat_prefetch_metadata_misses;
+ kstat_named_t arcstat_mru_hits;
+ kstat_named_t arcstat_mru_ghost_hits;
+ kstat_named_t arcstat_mfu_hits;
+ kstat_named_t arcstat_mfu_ghost_hits;
+ kstat_named_t arcstat_deleted;
+ kstat_named_t arcstat_recycle_miss;
+ kstat_named_t arcstat_mutex_miss;
+ kstat_named_t arcstat_evict_skip;
+ kstat_named_t arcstat_evict_l2_cached;
+ kstat_named_t arcstat_evict_l2_eligible;
+ kstat_named_t arcstat_evict_l2_ineligible;
+ kstat_named_t arcstat_hash_elements;
+ kstat_named_t arcstat_hash_elements_max;
+ kstat_named_t arcstat_hash_collisions;
+ kstat_named_t arcstat_hash_chains;
+ kstat_named_t arcstat_hash_chain_max;
+ kstat_named_t arcstat_p;
+ kstat_named_t arcstat_c;
+ kstat_named_t arcstat_c_min;
+ kstat_named_t arcstat_c_max;
+ kstat_named_t arcstat_size;
+ kstat_named_t arcstat_hdr_size;
+ kstat_named_t arcstat_data_size;
+ kstat_named_t arcstat_other_size;
+ kstat_named_t arcstat_l2_hits;
+ kstat_named_t arcstat_l2_misses;
+ kstat_named_t arcstat_l2_feeds;
+ kstat_named_t arcstat_l2_rw_clash;
+ kstat_named_t arcstat_l2_read_bytes;
+ kstat_named_t arcstat_l2_write_bytes;
+ kstat_named_t arcstat_l2_writes_sent;
+ kstat_named_t arcstat_l2_writes_done;
+ kstat_named_t arcstat_l2_writes_error;
+ kstat_named_t arcstat_l2_writes_hdr_miss;
+ kstat_named_t arcstat_l2_evict_lock_retry;
+ kstat_named_t arcstat_l2_evict_reading;
+ kstat_named_t arcstat_l2_free_on_write;
+ kstat_named_t arcstat_l2_abort_lowmem;
+ kstat_named_t arcstat_l2_cksum_bad;
+ kstat_named_t arcstat_l2_io_error;
+ kstat_named_t arcstat_l2_size;
+ kstat_named_t arcstat_l2_hdr_size;
+ kstat_named_t arcstat_memory_throttle_count;
+} arc_stats_t;
+
+static arc_stats_t arc_stats = {
+ { "hits", KSTAT_DATA_UINT64 },
+ { "misses", KSTAT_DATA_UINT64 },
+ { "demand_data_hits", KSTAT_DATA_UINT64 },
+ { "demand_data_misses", KSTAT_DATA_UINT64 },
+ { "demand_metadata_hits", KSTAT_DATA_UINT64 },
+ { "demand_metadata_misses", KSTAT_DATA_UINT64 },
+ { "prefetch_data_hits", KSTAT_DATA_UINT64 },
+ { "prefetch_data_misses", KSTAT_DATA_UINT64 },
+ { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
+ { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
+ { "mru_hits", KSTAT_DATA_UINT64 },
+ { "mru_ghost_hits", KSTAT_DATA_UINT64 },
+ { "mfu_hits", KSTAT_DATA_UINT64 },
+ { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
+ { "deleted", KSTAT_DATA_UINT64 },
+ { "recycle_miss", KSTAT_DATA_UINT64 },
+ { "mutex_miss", KSTAT_DATA_UINT64 },
+ { "evict_skip", KSTAT_DATA_UINT64 },
+ { "evict_l2_cached", KSTAT_DATA_UINT64 },
+ { "evict_l2_eligible", KSTAT_DATA_UINT64 },
+ { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
+ { "hash_elements", KSTAT_DATA_UINT64 },
+ { "hash_elements_max", KSTAT_DATA_UINT64 },
+ { "hash_collisions", KSTAT_DATA_UINT64 },
+ { "hash_chains", KSTAT_DATA_UINT64 },
+ { "hash_chain_max", KSTAT_DATA_UINT64 },
+ { "p", KSTAT_DATA_UINT64 },
+ { "c", KSTAT_DATA_UINT64 },
+ { "c_min", KSTAT_DATA_UINT64 },
+ { "c_max", KSTAT_DATA_UINT64 },
+ { "size", KSTAT_DATA_UINT64 },
+ { "hdr_size", KSTAT_DATA_UINT64 },
+ { "data_size", KSTAT_DATA_UINT64 },
+ { "other_size", KSTAT_DATA_UINT64 },
+ { "l2_hits", KSTAT_DATA_UINT64 },
+ { "l2_misses", KSTAT_DATA_UINT64 },
+ { "l2_feeds", KSTAT_DATA_UINT64 },
+ { "l2_rw_clash", KSTAT_DATA_UINT64 },
+ { "l2_read_bytes", KSTAT_DATA_UINT64 },
+ { "l2_write_bytes", KSTAT_DATA_UINT64 },
+ { "l2_writes_sent", KSTAT_DATA_UINT64 },
+ { "l2_writes_done", KSTAT_DATA_UINT64 },
+ { "l2_writes_error", KSTAT_DATA_UINT64 },
+ { "l2_writes_hdr_miss", KSTAT_DATA_UINT64 },
+ { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
+ { "l2_evict_reading", KSTAT_DATA_UINT64 },
+ { "l2_free_on_write", KSTAT_DATA_UINT64 },
+ { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
+ { "l2_cksum_bad", KSTAT_DATA_UINT64 },
+ { "l2_io_error", KSTAT_DATA_UINT64 },
+ { "l2_size", KSTAT_DATA_UINT64 },
+ { "l2_hdr_size", KSTAT_DATA_UINT64 },
+ { "memory_throttle_count", KSTAT_DATA_UINT64 }
+};
+
+#define ARCSTAT(stat) (arc_stats.stat.value.ui64)
+
+#define ARCSTAT_INCR(stat, val) \
+ atomic_add_64(&arc_stats.stat.value.ui64, (val));
+
+#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
+#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
+
+#define ARCSTAT_MAX(stat, val) { \
+ uint64_t m; \
+ while ((val) > (m = arc_stats.stat.value.ui64) && \
+ (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
+ continue; \
+}
+
+#define ARCSTAT_MAXSTAT(stat) \
+ ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
+
+/*
+ * We define a macro to allow ARC hits/misses to be easily broken down by
+ * two separate conditions, giving a total of four different subtypes for
+ * each of hits and misses (so eight statistics total).
+ */
+#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
+ if (cond1) { \
+ if (cond2) { \
+ ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
+ } else { \
+ ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
+ } \
+ } else { \
+ if (cond2) { \
+ ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
+ } else { \
+ ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
+ } \
+ }
+
+kstat_t *arc_ksp;
+static arc_state_t *arc_anon;
+static arc_state_t *arc_mru;
+static arc_state_t *arc_mru_ghost;
+static arc_state_t *arc_mfu;
+static arc_state_t *arc_mfu_ghost;
+static arc_state_t *arc_l2c_only;
+
+/*
+ * There are several ARC variables that are critical to export as kstats --
+ * but we don't want to have to grovel around in the kstat whenever we wish to
+ * manipulate them. For these variables, we therefore define them to be in
+ * terms of the statistic variable. This assures that we are not introducing
+ * the possibility of inconsistency by having shadow copies of the variables,
+ * while still allowing the code to be readable.
+ */
+#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
+#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
+#define arc_c ARCSTAT(arcstat_c) /* target size of cache */
+#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
+#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
+
+static int arc_no_grow; /* Don't try to grow cache size */
+static uint64_t arc_tempreserve;
+static uint64_t arc_loaned_bytes;
+static uint64_t arc_meta_used;
+static uint64_t arc_meta_limit;
+static uint64_t arc_meta_max = 0;
+
+typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
+
+typedef struct arc_callback arc_callback_t;
+
+struct arc_callback {
+ void *acb_private;
+ arc_done_func_t *acb_done;
+ arc_buf_t *acb_buf;
+ zio_t *acb_zio_dummy;
+ arc_callback_t *acb_next;
+};
+
+typedef struct arc_write_callback arc_write_callback_t;
+
+struct arc_write_callback {
+ void *awcb_private;
+ arc_done_func_t *awcb_ready;
+ arc_done_func_t *awcb_done;
+ arc_buf_t *awcb_buf;
+};
+
+struct arc_buf_hdr {
+ /* protected by hash lock */
+ dva_t b_dva;
+ uint64_t b_birth;
+ uint64_t b_cksum0;
+
+ kmutex_t b_freeze_lock;
+ zio_cksum_t *b_freeze_cksum;
+ void *b_thawed;
+
+ arc_buf_hdr_t *b_hash_next;
+ arc_buf_t *b_buf;
+ uint32_t b_flags;
+ uint32_t b_datacnt;
+
+ arc_callback_t *b_acb;
+ kcondvar_t b_cv;
+
+ /* immutable */
+ arc_buf_contents_t b_type;
+ uint64_t b_size;
+ uint64_t b_spa;
+
+ /* protected by arc state mutex */
+ arc_state_t *b_state;
+ list_node_t b_arc_node;
+
+ /* updated atomically */
+ clock_t b_arc_access;
+
+ /* self protecting */
+ refcount_t b_refcnt;
+
+ l2arc_buf_hdr_t *b_l2hdr;
+ list_node_t b_l2node;
+};
+
+static arc_buf_t *arc_eviction_list;
+static kmutex_t arc_eviction_mtx;
+static arc_buf_hdr_t arc_eviction_hdr;
+static void arc_get_data_buf(arc_buf_t *buf);
+static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
+static int arc_evict_needed(arc_buf_contents_t type);
+static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
+
+static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
+
+#define GHOST_STATE(state) \
+ ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
+ (state) == arc_l2c_only)
+
+/*
+ * Private ARC flags. These flags are private ARC only flags that will show up
+ * in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
+ * be passed in as arc_flags in things like arc_read. However, these flags
+ * should never be passed and should only be set by ARC code. When adding new
+ * public flags, make sure not to smash the private ones.
+ */
+
+#define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
+#define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
+#define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
+#define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
+#define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
+#define ARC_INDIRECT (1 << 14) /* this is an indirect block */
+#define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
+#define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
+#define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
+#define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
+
+#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
+#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
+#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
+#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
+#define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
+#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
+#define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
+#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
+#define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
+ (hdr)->b_l2hdr != NULL)
+#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
+#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
+#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
+
+/*
+ * Other sizes
+ */
+
+#define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
+#define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
+
+/*
+ * Hash table routines
+ */
+
+#define HT_LOCK_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(hdr) \
+ (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
+
+uint64_t zfs_crc64_table[256];
+
+/*
+ * Level 2 ARC
+ */
+
+#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
+#define L2ARC_HEADROOM 2 /* num of writes */
+#define L2ARC_FEED_SECS 1 /* caching interval secs */
+#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
+
+#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
+#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
+
+/*
+ * L2ARC Performance Tunables
+ */
+uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
+uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
+uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
+uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
+uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
+boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
+boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
+boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
+
+/*
+ * L2ARC Internals
+ */
+typedef struct l2arc_dev {
+ vdev_t *l2ad_vdev; /* vdev */
+ spa_t *l2ad_spa; /* spa */
+ uint64_t l2ad_hand; /* next write location */
+ uint64_t l2ad_write; /* desired write size, bytes */
+ uint64_t l2ad_boost; /* warmup write boost, bytes */
+ uint64_t l2ad_start; /* first addr on device */
+ uint64_t l2ad_end; /* last addr on device */
+ uint64_t l2ad_evict; /* last addr eviction reached */
+ boolean_t l2ad_first; /* first sweep through */
+ boolean_t l2ad_writing; /* currently writing */
+ list_t *l2ad_buflist; /* buffer list */
+ list_node_t l2ad_node; /* device list node */
+} l2arc_dev_t;
+
+static list_t L2ARC_dev_list; /* device list */
+static list_t *l2arc_dev_list; /* device list pointer */
+static kmutex_t l2arc_dev_mtx; /* device list mutex */
+static l2arc_dev_t *l2arc_dev_last; /* last device used */
+static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
+static list_t L2ARC_free_on_write; /* free after write buf list */
+static list_t *l2arc_free_on_write; /* free after write list ptr */
+static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
+static uint64_t l2arc_ndev; /* number of devices */
+
+typedef struct l2arc_read_callback {
+ arc_buf_t *l2rcb_buf; /* read buffer */
+ spa_t *l2rcb_spa; /* spa */
+ blkptr_t l2rcb_bp; /* original blkptr */
+ zbookmark_t l2rcb_zb; /* original bookmark */
+ int l2rcb_flags; /* original flags */
+} l2arc_read_callback_t;
+
+typedef struct l2arc_write_callback {
+ l2arc_dev_t *l2wcb_dev; /* device info */
+ arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
+} l2arc_write_callback_t;
+
+struct l2arc_buf_hdr {
+ /* protected by arc_buf_hdr mutex */
+ l2arc_dev_t *b_dev; /* L2ARC device */
+ uint64_t b_daddr; /* disk address, offset byte */
+};
+
+typedef struct l2arc_data_free {
+ /* protected by l2arc_free_on_write_mtx */
+ void *l2df_data;
+ size_t l2df_size;
+ void (*l2df_func)(void *, size_t);
+ list_node_t l2df_list_node;
+} l2arc_data_free_t;
+
+static kmutex_t l2arc_feed_thr_lock;
+static kcondvar_t l2arc_feed_thr_cv;
+static uint8_t l2arc_thread_exit;
+
+static void l2arc_read_done(zio_t *zio);
+static void l2arc_hdr_stat_add(void);
+static void l2arc_hdr_stat_remove(void);
+
+static uint64_t
+buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
+{
+ uint8_t *vdva = (uint8_t *)dva;
+ uint64_t crc = -1ULL;
+ int i;
+
+ ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
+
+ for (i = 0; i < sizeof (dva_t); i++)
+ crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
+
+ crc ^= (spa>>8) ^ birth;
+
+ return (crc);
+}
+
+#define BUF_EMPTY(buf) \
+ ((buf)->b_dva.dva_word[0] == 0 && \
+ (buf)->b_dva.dva_word[1] == 0 && \
+ (buf)->b_birth == 0)
+
+#define BUF_EQUAL(spa, dva, birth, buf) \
+ ((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
+ ((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
+ ((buf)->b_birth == birth) && ((buf)->b_spa == spa)
+
+static void
+buf_discard_identity(arc_buf_hdr_t *hdr)
+{
+ hdr->b_dva.dva_word[0] = 0;
+ hdr->b_dva.dva_word[1] = 0;
+ hdr->b_birth = 0;
+ hdr->b_cksum0 = 0;
+}
+
+static arc_buf_hdr_t *
+buf_hash_find(uint64_t spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp)
+{
+ uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
+ kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
+ arc_buf_hdr_t *buf;
+
+ mutex_enter(hash_lock);
+ for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
+ buf = buf->b_hash_next) {
+ if (BUF_EQUAL(spa, dva, birth, buf)) {
+ *lockp = hash_lock;
+ return (buf);
+ }
+ }
+ mutex_exit(hash_lock);
+ *lockp = NULL;
+ return (NULL);
+}
+
+/*
+ * Insert an entry into the hash table. If there is already an element
+ * equal to elem in the hash table, then the already existing element
+ * will be returned and the new element will not be inserted.
+ * Otherwise returns NULL.
+ */
+static arc_buf_hdr_t *
+buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
+{
+ uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
+ kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
+ arc_buf_hdr_t *fbuf;
+ uint32_t i;
+
+ ASSERT(!HDR_IN_HASH_TABLE(buf));
+ *lockp = hash_lock;
+ mutex_enter(hash_lock);
+ for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
+ fbuf = fbuf->b_hash_next, i++) {
+ if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
+ return (fbuf);
+ }
+
+ buf->b_hash_next = buf_hash_table.ht_table[idx];
+ buf_hash_table.ht_table[idx] = buf;
+ buf->b_flags |= ARC_IN_HASH_TABLE;
+
+ /* collect some hash table performance data */
+ if (i > 0) {
+ ARCSTAT_BUMP(arcstat_hash_collisions);
+ if (i == 1)
+ ARCSTAT_BUMP(arcstat_hash_chains);
+
+ ARCSTAT_MAX(arcstat_hash_chain_max, i);
+ }
+
+ ARCSTAT_BUMP(arcstat_hash_elements);
+ ARCSTAT_MAXSTAT(arcstat_hash_elements);
+
+ return (NULL);
+}
+
+static void
+buf_hash_remove(arc_buf_hdr_t *buf)
+{
+ arc_buf_hdr_t *fbuf, **bufp;
+ uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
+
+ ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
+ ASSERT(HDR_IN_HASH_TABLE(buf));
+
+ bufp = &buf_hash_table.ht_table[idx];
+ while ((fbuf = *bufp) != buf) {
+ ASSERT(fbuf != NULL);
+ bufp = &fbuf->b_hash_next;
+ }
+ *bufp = buf->b_hash_next;
+ buf->b_hash_next = NULL;
+ buf->b_flags &= ~ARC_IN_HASH_TABLE;
+
+ /* collect some hash table performance data */
+ ARCSTAT_BUMPDOWN(arcstat_hash_elements);
+
+ if (buf_hash_table.ht_table[idx] &&
+ buf_hash_table.ht_table[idx]->b_hash_next == NULL)
+ ARCSTAT_BUMPDOWN(arcstat_hash_chains);
+}
+
+/*
+ * Global data structures and functions for the buf kmem cache.
+ */
+static kmem_cache_t *hdr_cache;
+static kmem_cache_t *buf_cache;
+
+static void
+buf_fini(void)
+{
+ int i;
+
+ 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);
+ mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
+ arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
+
+ return (0);
+}
+
+/* ARGSUSED */
+static int
+buf_cons(void *vbuf, void *unused, int kmflag)
+{
+ arc_buf_t *buf = vbuf;
+
+ bzero(buf, sizeof (arc_buf_t));
+ mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
+ rw_init(&buf->b_data_lock, NULL, RW_DEFAULT, NULL);
+ arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
+
+ return (0);
+}
+
+/*
+ * Destructor callback - called when a cached buf is
+ * no longer required.
+ */
+/* ARGSUSED */
+static void
+hdr_dest(void *vbuf, void *unused)
+{
+ arc_buf_hdr_t *buf = vbuf;
+
+ ASSERT(BUF_EMPTY(buf));
+ refcount_destroy(&buf->b_refcnt);
+ cv_destroy(&buf->b_cv);
+ mutex_destroy(&buf->b_freeze_lock);
+ arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
+}
+
+/* ARGSUSED */
+static void
+buf_dest(void *vbuf, void *unused)
+{
+ arc_buf_t *buf = vbuf;
+
+ mutex_destroy(&buf->b_evict_lock);
+ rw_destroy(&buf->b_data_lock);
+ arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
+}
+
+/*
+ * Reclaim callback -- invoked when memory is low.
+ */
+/* ARGSUSED */
+static void
+hdr_recl(void *unused)
+{
+ dprintf("hdr_recl called\n");
+ /*
+ * umem calls the reclaim func when we destroy the buf cache,
+ * which is after we do arc_fini().
+ */
+ if (!arc_dead)
+ cv_signal(&arc_reclaim_thr_cv);
+}
+
+static void
+buf_init(void)
+{
+ uint64_t *ct;
+ uint64_t hsize = 1ULL << 12;
+ int i, j;
+
+ /*
+ * The hash table is big enough to fill all of physical memory
+ * with an average 64K block size. The table will take up
+ * totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
+ */
+ while (hsize * 65536 < physmem * PAGESIZE)
+ hsize <<= 1;
+retry:
+ buf_hash_table.ht_mask = hsize - 1;
+ 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, buf_cons, buf_dest, NULL, NULL, NULL, 0);
+
+ for (i = 0; i < 256; i++)
+ for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
+ *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
+
+ for (i = 0; i < BUF_LOCKS; i++) {
+ mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
+ NULL, MUTEX_DEFAULT, NULL);
+ }
+}
+
+#define ARC_MINTIME (hz>>4) /* 62 ms */
+
+static void
+arc_cksum_verify(arc_buf_t *buf)
+{
+ zio_cksum_t zc;
+
+ if (!(zfs_flags & ZFS_DEBUG_MODIFY))
+ return;
+
+ mutex_enter(&buf->b_hdr->b_freeze_lock);
+ if (buf->b_hdr->b_freeze_cksum == NULL ||
+ (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
+ mutex_exit(&buf->b_hdr->b_freeze_lock);
+ return;
+ }
+ fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
+ if (!ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc))
+ panic("buffer modified while frozen!");
+ mutex_exit(&buf->b_hdr->b_freeze_lock);
+}
+
+static int
+arc_cksum_equal(arc_buf_t *buf)
+{
+ zio_cksum_t zc;
+ int equal;
+
+ mutex_enter(&buf->b_hdr->b_freeze_lock);
+ fletcher_2_native(buf->b_data, buf->b_hdr->b_size, &zc);
+ equal = ZIO_CHECKSUM_EQUAL(*buf->b_hdr->b_freeze_cksum, zc);
+ mutex_exit(&buf->b_hdr->b_freeze_lock);
+
+ return (equal);
+}
+
+static void
+arc_cksum_compute(arc_buf_t *buf, boolean_t force)
+{
+ if (!force && !(zfs_flags & ZFS_DEBUG_MODIFY))
+ return;
+
+ mutex_enter(&buf->b_hdr->b_freeze_lock);
+ if (buf->b_hdr->b_freeze_cksum != NULL) {
+ mutex_exit(&buf->b_hdr->b_freeze_lock);
+ return;
+ }
+ buf->b_hdr->b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t), KM_SLEEP);
+ fletcher_2_native(buf->b_data, buf->b_hdr->b_size,
+ buf->b_hdr->b_freeze_cksum);
+ mutex_exit(&buf->b_hdr->b_freeze_lock);
+}
+
+void
+arc_buf_thaw(arc_buf_t *buf)
+{
+ if (zfs_flags & ZFS_DEBUG_MODIFY) {
+ if (buf->b_hdr->b_state != arc_anon)
+ panic("modifying non-anon buffer!");
+ if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
+ panic("modifying buffer while i/o in progress!");
+ arc_cksum_verify(buf);
+ }
+
+ mutex_enter(&buf->b_hdr->b_freeze_lock);
+ if (buf->b_hdr->b_freeze_cksum != NULL) {
+ kmem_free(buf->b_hdr->b_freeze_cksum, sizeof (zio_cksum_t));
+ buf->b_hdr->b_freeze_cksum = NULL;
+ }
+
+ if (zfs_flags & ZFS_DEBUG_MODIFY) {
+ if (buf->b_hdr->b_thawed)
+ kmem_free(buf->b_hdr->b_thawed, 1);
+ buf->b_hdr->b_thawed = kmem_alloc(1, KM_SLEEP);
+ }
+
+ mutex_exit(&buf->b_hdr->b_freeze_lock);
+}
+
+void
+arc_buf_freeze(arc_buf_t *buf)
+{
+ kmutex_t *hash_lock;
+
+ if (!(zfs_flags & ZFS_DEBUG_MODIFY))
+ return;
+
+ hash_lock = HDR_LOCK(buf->b_hdr);
+ mutex_enter(hash_lock);
+
+ ASSERT(buf->b_hdr->b_freeze_cksum != NULL ||
+ buf->b_hdr->b_state == arc_anon);
+ arc_cksum_compute(buf, B_FALSE);
+ mutex_exit(hash_lock);
+}
+
+static void
+add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
+{
+ ASSERT(MUTEX_HELD(hash_lock));
+
+ if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
+ (ab->b_state != arc_anon)) {
+ uint64_t delta = ab->b_size * ab->b_datacnt;
+ list_t *list = &ab->b_state->arcs_list[ab->b_type];
+ uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
+
+ ASSERT(!MUTEX_HELD(&ab->b_state->arcs_mtx));
+ mutex_enter(&ab->b_state->arcs_mtx);
+ ASSERT(list_link_active(&ab->b_arc_node));
+ list_remove(list, ab);
+ if (GHOST_STATE(ab->b_state)) {
+ ASSERT3U(ab->b_datacnt, ==, 0);
+ ASSERT3P(ab->b_buf, ==, NULL);
+ delta = ab->b_size;
+ }
+ ASSERT(delta > 0);
+ ASSERT3U(*size, >=, delta);
+ atomic_add_64(size, -delta);
+ mutex_exit(&ab->b_state->arcs_mtx);
+ /* remove the prefetch flag if we get a reference */
+ if (ab->b_flags & ARC_PREFETCH)
+ ab->b_flags &= ~ARC_PREFETCH;
+ }
+}
+
+static int
+remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
+{
+ int cnt;
+ arc_state_t *state = ab->b_state;
+
+ ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
+ ASSERT(!GHOST_STATE(state));
+
+ if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
+ (state != arc_anon)) {
+ uint64_t *size = &state->arcs_lsize[ab->b_type];
+
+ ASSERT(!MUTEX_HELD(&state->arcs_mtx));
+ mutex_enter(&state->arcs_mtx);
+ ASSERT(!list_link_active(&ab->b_arc_node));
+ list_insert_head(&state->arcs_list[ab->b_type], ab);
+ ASSERT(ab->b_datacnt > 0);
+ atomic_add_64(size, ab->b_size * ab->b_datacnt);
+ mutex_exit(&state->arcs_mtx);
+ }
+ return (cnt);
+}
+
+/*
+ * Move the supplied buffer to the indicated state. The mutex
+ * for the buffer must be held by the caller.
+ */
+static void
+arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
+{
+ arc_state_t *old_state = ab->b_state;
+ int64_t refcnt = refcount_count(&ab->b_refcnt);
+ uint64_t from_delta, to_delta;
+
+ ASSERT(MUTEX_HELD(hash_lock));
+ ASSERT(new_state != old_state);
+ ASSERT(refcnt == 0 || ab->b_datacnt > 0);
+ ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
+ ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
+
+ from_delta = to_delta = ab->b_datacnt * ab->b_size;
+
+ /*
+ * If this buffer is evictable, transfer it from the
+ * old state list to the new state list.
+ */
+ if (refcnt == 0) {
+ if (old_state != arc_anon) {
+ int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx);
+ uint64_t *size = &old_state->arcs_lsize[ab->b_type];
+
+ if (use_mutex)
+ mutex_enter(&old_state->arcs_mtx);
+
+ ASSERT(list_link_active(&ab->b_arc_node));
+ list_remove(&old_state->arcs_list[ab->b_type], ab);
+
+ /*
+ * If prefetching out of the ghost cache,
+ * we will have a non-zero datacnt.
+ */
+ if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
+ /* ghost elements have a ghost size */
+ ASSERT(ab->b_buf == NULL);
+ from_delta = ab->b_size;
+ }
+ ASSERT3U(*size, >=, from_delta);
+ atomic_add_64(size, -from_delta);
+
+ if (use_mutex)
+ mutex_exit(&old_state->arcs_mtx);
+ }
+ if (new_state != arc_anon) {
+ int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx);
+ uint64_t *size = &new_state->arcs_lsize[ab->b_type];
+
+ if (use_mutex)
+ mutex_enter(&new_state->arcs_mtx);
+
+ list_insert_head(&new_state->arcs_list[ab->b_type], ab);
+
+ /* ghost elements have a ghost size */
+ if (GHOST_STATE(new_state)) {
+ ASSERT(ab->b_datacnt == 0);
+ ASSERT(ab->b_buf == NULL);
+ to_delta = ab->b_size;
+ }
+ atomic_add_64(size, to_delta);
+
+ if (use_mutex)
+ mutex_exit(&new_state->arcs_mtx);
+ }
+ }
+
+ ASSERT(!BUF_EMPTY(ab));
+ if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
+ buf_hash_remove(ab);
+
+ /* adjust state sizes */
+ if (to_delta)
+ atomic_add_64(&new_state->arcs_size, to_delta);
+ if (from_delta) {
+ ASSERT3U(old_state->arcs_size, >=, from_delta);
+ atomic_add_64(&old_state->arcs_size, -from_delta);
+ }
+ ab->b_state = new_state;
+
+ /* adjust l2arc hdr stats */
+ if (new_state == arc_l2c_only)
+ l2arc_hdr_stat_add();
+ else if (old_state == arc_l2c_only)
+ l2arc_hdr_stat_remove();
+}
+
+void
+arc_space_consume(uint64_t space, arc_space_type_t type)
+{
+ ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
+
+ switch (type) {
+ case ARC_SPACE_DATA:
+ ARCSTAT_INCR(arcstat_data_size, space);
+ break;
+ case ARC_SPACE_OTHER:
+ ARCSTAT_INCR(arcstat_other_size, space);
+ break;
+ case ARC_SPACE_HDRS:
+ ARCSTAT_INCR(arcstat_hdr_size, space);
+ break;
+ case ARC_SPACE_L2HDRS:
+ ARCSTAT_INCR(arcstat_l2_hdr_size, space);
+ break;
+ }
+
+ atomic_add_64(&arc_meta_used, space);
+ atomic_add_64(&arc_size, space);
+}
+
+void
+arc_space_return(uint64_t space, arc_space_type_t type)
+{
+ ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
+
+ switch (type) {
+ case ARC_SPACE_DATA:
+ ARCSTAT_INCR(arcstat_data_size, -space);
+ break;
+ case ARC_SPACE_OTHER:
+ ARCSTAT_INCR(arcstat_other_size, -space);
+ break;
+ case ARC_SPACE_HDRS:
+ ARCSTAT_INCR(arcstat_hdr_size, -space);
+ break;
+ case ARC_SPACE_L2HDRS:
+ ARCSTAT_INCR(arcstat_l2_hdr_size, -space);
+ break;
+ }
+
+ ASSERT(arc_meta_used >= space);
+ if (arc_meta_max < arc_meta_used)
+ arc_meta_max = arc_meta_used;
+ atomic_add_64(&arc_meta_used, -space);
+ ASSERT(arc_size >= space);
+ atomic_add_64(&arc_size, -space);
+}
+
+void *
+arc_data_buf_alloc(uint64_t size)
+{
+ if (arc_evict_needed(ARC_BUFC_DATA))
+ cv_signal(&arc_reclaim_thr_cv);
+ atomic_add_64(&arc_size, size);
+ return (zio_data_buf_alloc(size));
+}
+
+void
+arc_data_buf_free(void *buf, uint64_t size)
+{
+ zio_data_buf_free(buf, size);
+ ASSERT(arc_size >= size);
+ atomic_add_64(&arc_size, -size);
+}
+
+arc_buf_t *
+arc_buf_alloc(spa_t *spa, int size, void *tag, arc_buf_contents_t type)
+{
+ arc_buf_hdr_t *hdr;
+ arc_buf_t *buf;
+
+ ASSERT3U(size, >, 0);
+ hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
+ ASSERT(BUF_EMPTY(hdr));
+ hdr->b_size = size;
+ hdr->b_type = type;
+ hdr->b_spa = spa_guid(spa);
+ hdr->b_state = arc_anon;
+ hdr->b_arc_access = 0;
+ buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
+ buf->b_hdr = hdr;
+ buf->b_data = NULL;
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+ buf->b_next = NULL;
+ hdr->b_buf = buf;
+ arc_get_data_buf(buf);
+ hdr->b_datacnt = 1;
+ hdr->b_flags = 0;
+ ASSERT(refcount_is_zero(&hdr->b_refcnt));
+ (void) refcount_add(&hdr->b_refcnt, tag);
+
+ return (buf);
+}
+
+static char *arc_onloan_tag = "onloan";
+
+/*
+ * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
+ * flight data by arc_tempreserve_space() until they are "returned". Loaned
+ * buffers must be returned to the arc before they can be used by the DMU or
+ * freed.
+ */
+arc_buf_t *
+arc_loan_buf(spa_t *spa, int size)
+{
+ arc_buf_t *buf;
+
+ buf = arc_buf_alloc(spa, size, arc_onloan_tag, ARC_BUFC_DATA);
+
+ atomic_add_64(&arc_loaned_bytes, size);
+ return (buf);
+}
+
+/*
+ * Return a loaned arc buffer to the arc.
+ */
+void
+arc_return_buf(arc_buf_t *buf, void *tag)
+{
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+
+ ASSERT(buf->b_data != NULL);
+ (void) refcount_add(&hdr->b_refcnt, tag);
+ (void) refcount_remove(&hdr->b_refcnt, arc_onloan_tag);
+
+ atomic_add_64(&arc_loaned_bytes, -hdr->b_size);
+}
+
+/* Detach an arc_buf from a dbuf (tag) */
+void
+arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
+{
+ arc_buf_hdr_t *hdr;
+
+ ASSERT(buf->b_data != NULL);
+ hdr = buf->b_hdr;
+ (void) refcount_add(&hdr->b_refcnt, arc_onloan_tag);
+ (void) refcount_remove(&hdr->b_refcnt, tag);
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+
+ atomic_add_64(&arc_loaned_bytes, hdr->b_size);
+}
+
+static arc_buf_t *
+arc_buf_clone(arc_buf_t *from)
+{
+ arc_buf_t *buf;
+ arc_buf_hdr_t *hdr = from->b_hdr;
+ uint64_t size = hdr->b_size;
+
+ ASSERT(hdr->b_state != arc_anon);
+
+ buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
+ buf->b_hdr = hdr;
+ buf->b_data = NULL;
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+ buf->b_next = hdr->b_buf;
+ hdr->b_buf = buf;
+ arc_get_data_buf(buf);
+ bcopy(from->b_data, buf->b_data, size);
+ hdr->b_datacnt += 1;
+ return (buf);
+}
+
+void
+arc_buf_add_ref(arc_buf_t *buf, void* tag)
+{
+ arc_buf_hdr_t *hdr;
+ kmutex_t *hash_lock;
+
+ /*
+ * Check to see if this buffer is evicted. Callers
+ * must verify b_data != NULL to know if the add_ref
+ * was successful.
+ */
+ mutex_enter(&buf->b_evict_lock);
+ if (buf->b_data == NULL) {
+ mutex_exit(&buf->b_evict_lock);
+ return;
+ }
+ hash_lock = HDR_LOCK(buf->b_hdr);
+ mutex_enter(hash_lock);
+ hdr = buf->b_hdr;
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+ mutex_exit(&buf->b_evict_lock);
+
+ ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
+ add_reference(hdr, hash_lock, tag);
+ DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
+ arc_access(hdr, hash_lock);
+ mutex_exit(hash_lock);
+ ARCSTAT_BUMP(arcstat_hits);
+ ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
+ demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
+ data, metadata, hits);
+}
+
+/*
+ * Free the arc data buffer. If it is an l2arc write in progress,
+ * the buffer is placed on l2arc_free_on_write to be freed later.
+ */
+static void
+arc_buf_data_free(arc_buf_hdr_t *hdr, void (*free_func)(void *, size_t),
+ void *data, size_t size)
+{
+ if (HDR_L2_WRITING(hdr)) {
+ l2arc_data_free_t *df;
+ df = kmem_alloc(sizeof (l2arc_data_free_t), KM_SLEEP);
+ df->l2df_data = data;
+ df->l2df_size = size;
+ df->l2df_func = free_func;
+ mutex_enter(&l2arc_free_on_write_mtx);
+ list_insert_head(l2arc_free_on_write, df);
+ mutex_exit(&l2arc_free_on_write_mtx);
+ ARCSTAT_BUMP(arcstat_l2_free_on_write);
+ } else {
+ free_func(data, size);
+ }
+}
+
+static void
+arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t all)
+{
+ arc_buf_t **bufp;
+
+ /* free up data associated with the buf */
+ if (buf->b_data) {
+ arc_state_t *state = buf->b_hdr->b_state;
+ uint64_t size = buf->b_hdr->b_size;
+ arc_buf_contents_t type = buf->b_hdr->b_type;
+
+ arc_cksum_verify(buf);
+
+ if (!recycle) {
+ if (type == ARC_BUFC_METADATA) {
+ arc_buf_data_free(buf->b_hdr, zio_buf_free,
+ buf->b_data, size);
+ arc_space_return(size, ARC_SPACE_DATA);
+ } else {
+ ASSERT(type == ARC_BUFC_DATA);
+ arc_buf_data_free(buf->b_hdr,
+ zio_data_buf_free, buf->b_data, size);
+ ARCSTAT_INCR(arcstat_data_size, -size);
+ atomic_add_64(&arc_size, -size);
+ }
+ }
+ if (list_link_active(&buf->b_hdr->b_arc_node)) {
+ uint64_t *cnt = &state->arcs_lsize[type];
+
+ ASSERT(refcount_is_zero(&buf->b_hdr->b_refcnt));
+ ASSERT(state != arc_anon);
+
+ ASSERT3U(*cnt, >=, size);
+ atomic_add_64(cnt, -size);
+ }
+ ASSERT3U(state->arcs_size, >=, size);
+ atomic_add_64(&state->arcs_size, -size);
+ buf->b_data = NULL;
+ ASSERT(buf->b_hdr->b_datacnt > 0);
+ buf->b_hdr->b_datacnt -= 1;
+ }
+
+ /* only remove the buf if requested */
+ if (!all)
+ return;
+
+ /* remove the buf from the hdr list */
+ for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
+ continue;
+ *bufp = buf->b_next;
+ buf->b_next = NULL;
+
+ ASSERT(buf->b_efunc == NULL);
+
+ /* clean up the buf */
+ buf->b_hdr = NULL;
+ kmem_cache_free(buf_cache, buf);
+}
+
+static void
+arc_hdr_destroy(arc_buf_hdr_t *hdr)
+{
+ ASSERT(refcount_is_zero(&hdr->b_refcnt));
+ ASSERT3P(hdr->b_state, ==, arc_anon);
+ ASSERT(!HDR_IO_IN_PROGRESS(hdr));
+ l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
+
+ if (l2hdr != NULL) {
+ boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
+ /*
+ * To prevent arc_free() and l2arc_evict() from
+ * attempting to free the same buffer at the same time,
+ * a FREE_IN_PROGRESS flag is given to arc_free() to
+ * give it priority. l2arc_evict() can't destroy this
+ * header while we are waiting on l2arc_buflist_mtx.
+ *
+ * The hdr may be removed from l2ad_buflist before we
+ * grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
+ */
+ if (!buflist_held) {
+ mutex_enter(&l2arc_buflist_mtx);
+ l2hdr = hdr->b_l2hdr;
+ }
+
+ if (l2hdr != NULL) {
+ list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
+ ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
+ kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
+ if (hdr->b_state == arc_l2c_only)
+ l2arc_hdr_stat_remove();
+ hdr->b_l2hdr = NULL;
+ }
+
+ if (!buflist_held)
+ mutex_exit(&l2arc_buflist_mtx);
+ }
+
+ if (!BUF_EMPTY(hdr)) {
+ ASSERT(!HDR_IN_HASH_TABLE(hdr));
+ buf_discard_identity(hdr);
+ }
+ while (hdr->b_buf) {
+ arc_buf_t *buf = hdr->b_buf;
+
+ if (buf->b_efunc) {
+ mutex_enter(&arc_eviction_mtx);
+ mutex_enter(&buf->b_evict_lock);
+ ASSERT(buf->b_hdr != NULL);
+ arc_buf_destroy(hdr->b_buf, FALSE, FALSE);
+ hdr->b_buf = buf->b_next;
+ buf->b_hdr = &arc_eviction_hdr;
+ buf->b_next = arc_eviction_list;
+ arc_eviction_list = buf;
+ mutex_exit(&buf->b_evict_lock);
+ mutex_exit(&arc_eviction_mtx);
+ } else {
+ arc_buf_destroy(hdr->b_buf, FALSE, TRUE);
+ }
+ }
+ if (hdr->b_freeze_cksum != NULL) {
+ kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
+ hdr->b_freeze_cksum = NULL;
+ }
+ if (hdr->b_thawed) {
+ kmem_free(hdr->b_thawed, 1);
+ hdr->b_thawed = NULL;
+ }
+
+ ASSERT(!list_link_active(&hdr->b_arc_node));
+ ASSERT3P(hdr->b_hash_next, ==, NULL);
+ ASSERT3P(hdr->b_acb, ==, NULL);
+ kmem_cache_free(hdr_cache, hdr);
+}
+
+void
+arc_buf_free(arc_buf_t *buf, void *tag)
+{
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+ int hashed = hdr->b_state != arc_anon;
+
+ ASSERT(buf->b_efunc == NULL);
+ ASSERT(buf->b_data != NULL);
+
+ if (hashed) {
+ kmutex_t *hash_lock = HDR_LOCK(hdr);
+
+ mutex_enter(hash_lock);
+ hdr = buf->b_hdr;
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+
+ (void) remove_reference(hdr, hash_lock, tag);
+ if (hdr->b_datacnt > 1) {
+ arc_buf_destroy(buf, FALSE, TRUE);
+ } else {
+ ASSERT(buf == hdr->b_buf);
+ ASSERT(buf->b_efunc == NULL);
+ hdr->b_flags |= ARC_BUF_AVAILABLE;
+ }
+ mutex_exit(hash_lock);
+ } else if (HDR_IO_IN_PROGRESS(hdr)) {
+ int destroy_hdr;
+ /*
+ * We are in the middle of an async write. Don't destroy
+ * this buffer unless the write completes before we finish
+ * decrementing the reference count.
+ */
+ mutex_enter(&arc_eviction_mtx);
+ (void) remove_reference(hdr, NULL, tag);
+ ASSERT(refcount_is_zero(&hdr->b_refcnt));
+ destroy_hdr = !HDR_IO_IN_PROGRESS(hdr);
+ mutex_exit(&arc_eviction_mtx);
+ if (destroy_hdr)
+ arc_hdr_destroy(hdr);
+ } else {
+ if (remove_reference(hdr, NULL, tag) > 0)
+ arc_buf_destroy(buf, FALSE, TRUE);
+ else
+ arc_hdr_destroy(hdr);
+ }
+}
+
+int
+arc_buf_remove_ref(arc_buf_t *buf, void* tag)
+{
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+ kmutex_t *hash_lock = HDR_LOCK(hdr);
+ int no_callback = (buf->b_efunc == NULL);
+
+ if (hdr->b_state == arc_anon) {
+ ASSERT(hdr->b_datacnt == 1);
+ arc_buf_free(buf, tag);
+ return (no_callback);
+ }
+
+ mutex_enter(hash_lock);
+ hdr = buf->b_hdr;
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+ ASSERT(hdr->b_state != arc_anon);
+ ASSERT(buf->b_data != NULL);
+
+ (void) remove_reference(hdr, hash_lock, tag);
+ if (hdr->b_datacnt > 1) {
+ if (no_callback)
+ arc_buf_destroy(buf, FALSE, TRUE);
+ } else if (no_callback) {
+ ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
+ ASSERT(buf->b_efunc == NULL);
+ hdr->b_flags |= ARC_BUF_AVAILABLE;
+ }
+ ASSERT(no_callback || hdr->b_datacnt > 1 ||
+ refcount_is_zero(&hdr->b_refcnt));
+ mutex_exit(hash_lock);
+ return (no_callback);
+}
+
+int
+arc_buf_size(arc_buf_t *buf)
+{
+ return (buf->b_hdr->b_size);
+}
+
+/*
+ * Evict buffers from list until we've removed the specified number of
+ * bytes. Move the removed buffers to the appropriate evict state.
+ * If the recycle flag is set, then attempt to "recycle" a buffer:
+ * - look for a buffer to evict that is `bytes' long.
+ * - return the data block from this buffer rather than freeing it.
+ * This flag is used by callers that are trying to make space for a
+ * new buffer in a full arc cache.
+ *
+ * This function makes a "best effort". It skips over any buffers
+ * it can't get a hash_lock on, and so may not catch all candidates.
+ * It may also return without evicting as much space as requested.
+ */
+static void *
+arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
+ arc_buf_contents_t type)
+{
+ arc_state_t *evicted_state;
+ uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
+ arc_buf_hdr_t *ab, *ab_prev = NULL;
+ list_t *list = &state->arcs_list[type];
+ kmutex_t *hash_lock;
+ boolean_t have_lock;
+ void *stolen = NULL;
+
+ ASSERT(state == arc_mru || state == arc_mfu);
+
+ evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
+
+ mutex_enter(&state->arcs_mtx);
+ mutex_enter(&evicted_state->arcs_mtx);
+
+ for (ab = list_tail(list); ab; ab = ab_prev) {
+ ab_prev = list_prev(list, ab);
+ /* prefetch buffers have a minimum lifespan */
+ if (HDR_IO_IN_PROGRESS(ab) ||
+ (spa && ab->b_spa != spa) ||
+ (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
+ ddi_get_lbolt() - ab->b_arc_access <
+ arc_min_prefetch_lifespan)) {
+ skipped++;
+ continue;
+ }
+ /* "lookahead" for better eviction candidate */
+ if (recycle && ab->b_size != bytes &&
+ ab_prev && ab_prev->b_size == bytes)
+ continue;
+ hash_lock = HDR_LOCK(ab);
+ have_lock = MUTEX_HELD(hash_lock);
+ if (have_lock || mutex_tryenter(hash_lock)) {
+ ASSERT3U(refcount_count(&ab->b_refcnt), ==, 0);
+ ASSERT(ab->b_datacnt > 0);
+ while (ab->b_buf) {
+ arc_buf_t *buf = ab->b_buf;
+ if (!mutex_tryenter(&buf->b_evict_lock)) {
+ missed += 1;
+ break;
+ }
+ if (buf->b_data) {
+ bytes_evicted += ab->b_size;
+ if (recycle && ab->b_type == type &&
+ ab->b_size == bytes &&
+ !HDR_L2_WRITING(ab)) {
+ stolen = buf->b_data;
+ recycle = FALSE;
+ }
+ }
+ if (buf->b_efunc) {
+ mutex_enter(&arc_eviction_mtx);
+ arc_buf_destroy(buf,
+ buf->b_data == stolen, FALSE);
+ ab->b_buf = buf->b_next;
+ buf->b_hdr = &arc_eviction_hdr;
+ buf->b_next = arc_eviction_list;
+ arc_eviction_list = buf;
+ mutex_exit(&arc_eviction_mtx);
+ mutex_exit(&buf->b_evict_lock);
+ } else {
+ mutex_exit(&buf->b_evict_lock);
+ arc_buf_destroy(buf,
+ buf->b_data == stolen, TRUE);
+ }
+ }
+
+ if (ab->b_l2hdr) {
+ ARCSTAT_INCR(arcstat_evict_l2_cached,
+ ab->b_size);
+ } else {
+ if (l2arc_write_eligible(ab->b_spa, ab)) {
+ ARCSTAT_INCR(arcstat_evict_l2_eligible,
+ ab->b_size);
+ } else {
+ ARCSTAT_INCR(
+ arcstat_evict_l2_ineligible,
+ ab->b_size);
+ }
+ }
+
+ if (ab->b_datacnt == 0) {
+ arc_change_state(evicted_state, ab, hash_lock);
+ ASSERT(HDR_IN_HASH_TABLE(ab));
+ ab->b_flags |= ARC_IN_HASH_TABLE;
+ ab->b_flags &= ~ARC_BUF_AVAILABLE;
+ DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
+ }
+ if (!have_lock)
+ mutex_exit(hash_lock);
+ if (bytes >= 0 && bytes_evicted >= bytes)
+ break;
+ } else {
+ missed += 1;
+ }
+ }
+
+ mutex_exit(&evicted_state->arcs_mtx);
+ mutex_exit(&state->arcs_mtx);
+
+ if (bytes_evicted < bytes)
+ dprintf("only evicted %lld bytes from %x",
+ (longlong_t)bytes_evicted, state);
+
+ if (skipped)
+ ARCSTAT_INCR(arcstat_evict_skip, skipped);
+
+ if (missed)
+ ARCSTAT_INCR(arcstat_mutex_miss, missed);
+
+ /*
+ * We have just evicted some date into the ghost state, make
+ * sure we also adjust the ghost state size if necessary.
+ */
+ if (arc_no_grow &&
+ arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size > arc_c) {
+ int64_t mru_over = arc_anon->arcs_size + arc_mru->arcs_size +
+ arc_mru_ghost->arcs_size - arc_c;
+
+ if (mru_over > 0 && arc_mru_ghost->arcs_lsize[type] > 0) {
+ int64_t todelete =
+ MIN(arc_mru_ghost->arcs_lsize[type], mru_over);
+ arc_evict_ghost(arc_mru_ghost, NULL, todelete);
+ } else if (arc_mfu_ghost->arcs_lsize[type] > 0) {
+ int64_t todelete = MIN(arc_mfu_ghost->arcs_lsize[type],
+ arc_mru_ghost->arcs_size +
+ arc_mfu_ghost->arcs_size - arc_c);
+ arc_evict_ghost(arc_mfu_ghost, NULL, todelete);
+ }
+ }
+
+ return (stolen);
+}
+
+/*
+ * Remove buffers from list until we've removed the specified number of
+ * bytes. Destroy the buffers that are removed.
+ */
+static void
+arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
+{
+ arc_buf_hdr_t *ab, *ab_prev;
+ arc_buf_hdr_t marker = { 0 };
+ list_t *list = &state->arcs_list[ARC_BUFC_DATA];
+ kmutex_t *hash_lock;
+ uint64_t bytes_deleted = 0;
+ uint64_t bufs_skipped = 0;
+
+ ASSERT(GHOST_STATE(state));
+top:
+ mutex_enter(&state->arcs_mtx);
+ for (ab = list_tail(list); ab; ab = ab_prev) {
+ ab_prev = list_prev(list, ab);
+ if (spa && ab->b_spa != spa)
+ continue;
+
+ /* ignore markers */
+ if (ab->b_spa == 0)
+ continue;
+
+ hash_lock = HDR_LOCK(ab);
+ /* caller may be trying to modify this buffer, skip it */
+ if (MUTEX_HELD(hash_lock))
+ continue;
+ if (mutex_tryenter(hash_lock)) {
+ ASSERT(!HDR_IO_IN_PROGRESS(ab));
+ ASSERT(ab->b_buf == NULL);
+ ARCSTAT_BUMP(arcstat_deleted);
+ bytes_deleted += ab->b_size;
+
+ if (ab->b_l2hdr != NULL) {
+ /*
+ * This buffer is cached on the 2nd Level ARC;
+ * don't destroy the header.
+ */
+ arc_change_state(arc_l2c_only, ab, hash_lock);
+ mutex_exit(hash_lock);
+ } else {
+ arc_change_state(arc_anon, ab, hash_lock);
+ mutex_exit(hash_lock);
+ arc_hdr_destroy(ab);
+ }
+
+ DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
+ if (bytes >= 0 && bytes_deleted >= bytes)
+ break;
+ } else if (bytes < 0) {
+ /*
+ * Insert a list marker and then wait for the
+ * hash lock to become available. Once its
+ * available, restart from where we left off.
+ */
+ list_insert_after(list, ab, &marker);
+ mutex_exit(&state->arcs_mtx);
+ mutex_enter(hash_lock);
+ mutex_exit(hash_lock);
+ mutex_enter(&state->arcs_mtx);
+ ab_prev = list_prev(list, &marker);
+ list_remove(list, &marker);
+ } else
+ bufs_skipped += 1;
+ }
+ mutex_exit(&state->arcs_mtx);
+
+ if (list == &state->arcs_list[ARC_BUFC_DATA] &&
+ (bytes < 0 || bytes_deleted < bytes)) {
+ list = &state->arcs_list[ARC_BUFC_METADATA];
+ goto top;
+ }
+
+ if (bufs_skipped) {
+ ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
+ ASSERT(bytes >= 0);
+ }
+
+ if (bytes_deleted < bytes)
+ dprintf("only deleted %lld bytes from %p",
+ (longlong_t)bytes_deleted, state);
+}
+
+static void
+arc_adjust(void)
+{
+ int64_t adjustment, delta;
+
+ /*
+ * Adjust MRU size
+ */
+
+ adjustment = MIN((int64_t)(arc_size - arc_c),
+ (int64_t)(arc_anon->arcs_size + arc_mru->arcs_size + arc_meta_used -
+ arc_p));
+
+ if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_DATA] > 0) {
+ delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_DATA], adjustment);
+ (void) arc_evict(arc_mru, NULL, delta, FALSE, ARC_BUFC_DATA);
+ adjustment -= delta;
+ }
+
+ if (adjustment > 0 && arc_mru->arcs_lsize[ARC_BUFC_METADATA] > 0) {
+ delta = MIN(arc_mru->arcs_lsize[ARC_BUFC_METADATA], adjustment);
+ (void) arc_evict(arc_mru, NULL, delta, FALSE,
+ ARC_BUFC_METADATA);
+ }
+
+ /*
+ * Adjust MFU size
+ */
+
+ adjustment = arc_size - arc_c;
+
+ if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_DATA] > 0) {
+ delta = MIN(adjustment, arc_mfu->arcs_lsize[ARC_BUFC_DATA]);
+ (void) arc_evict(arc_mfu, NULL, delta, FALSE, ARC_BUFC_DATA);
+ adjustment -= delta;
+ }
+
+ if (adjustment > 0 && arc_mfu->arcs_lsize[ARC_BUFC_METADATA] > 0) {
+ int64_t delta = MIN(adjustment,
+ arc_mfu->arcs_lsize[ARC_BUFC_METADATA]);
+ (void) arc_evict(arc_mfu, NULL, delta, FALSE,
+ ARC_BUFC_METADATA);
+ }
+
+ /*
+ * Adjust ghost lists
+ */
+
+ adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
+
+ if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
+ delta = MIN(arc_mru_ghost->arcs_size, adjustment);
+ arc_evict_ghost(arc_mru_ghost, NULL, delta);
+ }
+
+ adjustment =
+ arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
+
+ if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
+ delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
+ arc_evict_ghost(arc_mfu_ghost, NULL, delta);
+ }
+}
+
+static void
+arc_do_user_evicts(void)
+{
+ mutex_enter(&arc_eviction_mtx);
+ while (arc_eviction_list != NULL) {
+ arc_buf_t *buf = arc_eviction_list;
+ arc_eviction_list = buf->b_next;
+ mutex_enter(&buf->b_evict_lock);
+ buf->b_hdr = NULL;
+ mutex_exit(&buf->b_evict_lock);
+ mutex_exit(&arc_eviction_mtx);
+
+ if (buf->b_efunc != NULL)
+ VERIFY(buf->b_efunc(buf) == 0);
+
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+ kmem_cache_free(buf_cache, buf);
+ mutex_enter(&arc_eviction_mtx);
+ }
+ mutex_exit(&arc_eviction_mtx);
+}
+
+/*
+ * Flush all *evictable* data from the cache for the given spa.
+ * NOTE: this will not touch "active" (i.e. referenced) data.
+ */
+void
+arc_flush(spa_t *spa)
+{
+ uint64_t guid = 0;
+
+ if (spa)
+ guid = spa_guid(spa);
+
+ while (list_head(&arc_mru->arcs_list[ARC_BUFC_DATA])) {
+ (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_DATA);
+ if (spa)
+ break;
+ }
+ while (list_head(&arc_mru->arcs_list[ARC_BUFC_METADATA])) {
+ (void) arc_evict(arc_mru, guid, -1, FALSE, ARC_BUFC_METADATA);
+ if (spa)
+ break;
+ }
+ while (list_head(&arc_mfu->arcs_list[ARC_BUFC_DATA])) {
+ (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_DATA);
+ if (spa)
+ break;
+ }
+ while (list_head(&arc_mfu->arcs_list[ARC_BUFC_METADATA])) {
+ (void) arc_evict(arc_mfu, guid, -1, FALSE, ARC_BUFC_METADATA);
+ if (spa)
+ break;
+ }
+
+ arc_evict_ghost(arc_mru_ghost, guid, -1);
+ arc_evict_ghost(arc_mfu_ghost, guid, -1);
+
+ mutex_enter(&arc_reclaim_thr_lock);
+ arc_do_user_evicts();
+ mutex_exit(&arc_reclaim_thr_lock);
+ ASSERT(spa || arc_eviction_list == NULL);
+}
+
+void
+arc_shrink(void)
+{
+ if (arc_c > arc_c_min) {
+ uint64_t to_free;
+
+#ifdef _KERNEL
+ to_free = MAX(arc_c >> arc_shrink_shift, ptob(needfree));
+#else
+ to_free = arc_c >> arc_shrink_shift;
+#endif
+ if (arc_c > arc_c_min + to_free)
+ atomic_add_64(&arc_c, -to_free);
+ else
+ arc_c = arc_c_min;
+
+ atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
+ if (arc_c > arc_size)
+ arc_c = MAX(arc_size, arc_c_min);
+ if (arc_p > arc_c)
+ arc_p = (arc_c >> 1);
+ ASSERT(arc_c >= arc_c_min);
+ ASSERT((int64_t)arc_p >= 0);
+ }
+
+ if (arc_size > arc_c)
+ arc_adjust();
+}
+
+static int
+arc_reclaim_needed(void)
+{
+ 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 succeed. anon_resvmem() checks that the
+ * availrmem is greater than swapfs_minfree, and the number of reserved
+ * swap pages. We also add a bit of extra here just to prevent
+ * circumstances from getting really dire.
+ */
+ if (availrmem < swapfs_minfree + swapfs_reserve + extra)
+ return (1);
+
+#if defined(__i386)
+ /*
+ * If we're on an i386 platform, it's possible that we'll exhaust the
+ * kernel heap space before we ever run out of available physical
+ * memory. Most checks of the size of the heap_area compare against
+ * tune.t_minarmem, which is the minimum available real memory that we
+ * can have in the system. However, this is generally fixed at 25 pages
+ * which is so low that it's useless. In this comparison, we seek to
+ * calculate the total heap-size, and reclaim if more than 3/4ths of the
+ * heap is allocated. (Or, in the calculation, if less than 1/4th is
+ * free)
+ */
+ if (btop(vmem_size(heap_arena, VMEM_FREE)) <
+ (btop(vmem_size(heap_arena, VMEM_FREE | VMEM_ALLOC)) >> 2))
+ return (1);
+#endif
+
+#else
+ if (spa_get_random(100) == 0)
+ return (1);
+#endif
+ return (0);
+}
+
+static void
+arc_kmem_reap_now(arc_reclaim_strategy_t strat)
+{
+ size_t i;
+ kmem_cache_t *prev_cache = NULL;
+ kmem_cache_t *prev_data_cache = NULL;
+ extern kmem_cache_t *zio_buf_cache[];
+ extern kmem_cache_t *zio_data_buf_cache[];
+
+#ifdef _KERNEL
+ if (arc_meta_used >= arc_meta_limit) {
+ /*
+ * We are exceeding our meta-data cache limit.
+ * Purge some DNLC entries to release holds on meta-data.
+ */
+ dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
+ }
+#if defined(__i386)
+ /*
+ * Reclaim unused memory from all kmem caches.
+ */
+ kmem_reap();
+#endif
+#endif
+
+ /*
+ * An aggressive reclamation will shrink the cache size as well as
+ * reap free buffers from the arc kmem caches.
+ */
+ if (strat == ARC_RECLAIM_AGGR)
+ arc_shrink();
+
+ for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
+ if (zio_buf_cache[i] != prev_cache) {
+ prev_cache = zio_buf_cache[i];
+ kmem_cache_reap_now(zio_buf_cache[i]);
+ }
+ if (zio_data_buf_cache[i] != prev_data_cache) {
+ prev_data_cache = zio_data_buf_cache[i];
+ kmem_cache_reap_now(zio_data_buf_cache[i]);
+ }
+ }
+ kmem_cache_reap_now(buf_cache);
+ kmem_cache_reap_now(hdr_cache);
+}
+
+static void
+arc_reclaim_thread(void)
+{
+ clock_t growtime = 0;
+ arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
+ callb_cpr_t cpr;
+
+ CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
+
+ mutex_enter(&arc_reclaim_thr_lock);
+ while (arc_thread_exit == 0) {
+ if (arc_reclaim_needed()) {
+
+ if (arc_no_grow) {
+ if (last_reclaim == ARC_RECLAIM_CONS) {
+ last_reclaim = ARC_RECLAIM_AGGR;
+ } else {
+ last_reclaim = ARC_RECLAIM_CONS;
+ }
+ } else {
+ arc_no_grow = TRUE;
+ last_reclaim = ARC_RECLAIM_AGGR;
+ membar_producer();
+ }
+
+ /* reset the growth delay for every reclaim */
+ growtime = ddi_get_lbolt() + (arc_grow_retry * hz);
+
+ arc_kmem_reap_now(last_reclaim);
+ arc_warm = B_TRUE;
+
+ } else if (arc_no_grow && ddi_get_lbolt() >= growtime) {
+ arc_no_grow = FALSE;
+ }
+
+ arc_adjust();
+
+ if (arc_eviction_list != NULL)
+ arc_do_user_evicts();
+
+ /* block until needed, or one second, whichever is shorter */
+ CALLB_CPR_SAFE_BEGIN(&cpr);
+ (void) cv_timedwait(&arc_reclaim_thr_cv,
+ &arc_reclaim_thr_lock, (ddi_get_lbolt() + hz));
+ CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
+ }
+
+ arc_thread_exit = 0;
+ cv_broadcast(&arc_reclaim_thr_cv);
+ CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
+ thread_exit();
+}
+
+/*
+ * Adapt arc info given the number of bytes we are trying to add and
+ * the state that we are comming from. This function is only called
+ * when we are adding new content to the cache.
+ */
+static void
+arc_adapt(int bytes, arc_state_t *state)
+{
+ int mult;
+ uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
+
+ if (state == arc_l2c_only)
+ return;
+
+ ASSERT(bytes > 0);
+ /*
+ * Adapt the target size of the MRU list:
+ * - if we just hit in the MRU ghost list, then increase
+ * the target size of the MRU list.
+ * - if we just hit in the MFU ghost list, then increase
+ * the target size of the MFU list by decreasing the
+ * target size of the MRU list.
+ */
+ if (state == arc_mru_ghost) {
+ mult = ((arc_mru_ghost->arcs_size >= arc_mfu_ghost->arcs_size) ?
+ 1 : (arc_mfu_ghost->arcs_size/arc_mru_ghost->arcs_size));
+ mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
+
+ arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
+ } else if (state == arc_mfu_ghost) {
+ uint64_t delta;
+
+ mult = ((arc_mfu_ghost->arcs_size >= arc_mru_ghost->arcs_size) ?
+ 1 : (arc_mru_ghost->arcs_size/arc_mfu_ghost->arcs_size));
+ mult = MIN(mult, 10);
+
+ delta = MIN(bytes * mult, arc_p);
+ arc_p = MAX(arc_p_min, arc_p - delta);
+ }
+ ASSERT((int64_t)arc_p >= 0);
+
+ if (arc_reclaim_needed()) {
+ cv_signal(&arc_reclaim_thr_cv);
+ return;
+ }
+
+ if (arc_no_grow)
+ return;
+
+ if (arc_c >= arc_c_max)
+ return;
+
+ /*
+ * If we're within (2 * maxblocksize) bytes of the target
+ * cache size, increment the target cache size
+ */
+ if (arc_size > arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) {
+ atomic_add_64(&arc_c, (int64_t)bytes);
+ if (arc_c > arc_c_max)
+ arc_c = arc_c_max;
+ else if (state == arc_anon)
+ atomic_add_64(&arc_p, (int64_t)bytes);
+ if (arc_p > arc_c)
+ arc_p = arc_c;
+ }
+ ASSERT((int64_t)arc_p >= 0);
+}
+
+/*
+ * Check if the cache has reached its limits and eviction is required
+ * prior to insert.
+ */
+static int
+arc_evict_needed(arc_buf_contents_t type)
+{
+ if (type == ARC_BUFC_METADATA && arc_meta_used >= arc_meta_limit)
+ return (1);
+
+#ifdef _KERNEL
+ /*
+ * If zio data pages are being allocated out of a separate heap segment,
+ * then enforce that the size of available vmem for this area remains
+ * above about 1/32nd free.
+ */
+ if (type == ARC_BUFC_DATA && zio_arena != NULL &&
+ vmem_size(zio_arena, VMEM_FREE) <
+ (vmem_size(zio_arena, VMEM_ALLOC) >> 5))
+ return (1);
+#endif
+
+ if (arc_reclaim_needed())
+ return (1);
+
+ return (arc_size > arc_c);
+}
+
+/*
+ * The buffer, supplied as the first argument, needs a data block.
+ * So, if we are at cache max, determine which cache should be victimized.
+ * We have the following cases:
+ *
+ * 1. Insert for MRU, p > sizeof(arc_anon + arc_mru) ->
+ * In this situation if we're out of space, but the resident size of the MFU is
+ * under the limit, victimize the MFU cache to satisfy this insertion request.
+ *
+ * 2. Insert for MRU, p <= sizeof(arc_anon + arc_mru) ->
+ * Here, we've used up all of the available space for the MRU, so we need to
+ * evict from our own cache instead. Evict from the set of resident MRU
+ * entries.
+ *
+ * 3. Insert for MFU (c - p) > sizeof(arc_mfu) ->
+ * c minus p represents the MFU space in the cache, since p is the size of the
+ * cache that is dedicated to the MRU. In this situation there's still space on
+ * the MFU side, so the MRU side needs to be victimized.
+ *
+ * 4. Insert for MFU (c - p) < sizeof(arc_mfu) ->
+ * MFU's resident set is consuming more space than it has been allotted. In
+ * this situation, we must victimize our own cache, the MFU, for this insertion.
+ */
+static void
+arc_get_data_buf(arc_buf_t *buf)
+{
+ arc_state_t *state = buf->b_hdr->b_state;
+ uint64_t size = buf->b_hdr->b_size;
+ arc_buf_contents_t type = buf->b_hdr->b_type;
+
+ arc_adapt(size, state);
+
+ /*
+ * We have not yet reached cache maximum size,
+ * just allocate a new buffer.
+ */
+ if (!arc_evict_needed(type)) {
+ if (type == ARC_BUFC_METADATA) {
+ buf->b_data = zio_buf_alloc(size);
+ arc_space_consume(size, ARC_SPACE_DATA);
+ } else {
+ ASSERT(type == ARC_BUFC_DATA);
+ buf->b_data = zio_data_buf_alloc(size);
+ ARCSTAT_INCR(arcstat_data_size, size);
+ atomic_add_64(&arc_size, size);
+ }
+ goto out;
+ }
+
+ /*
+ * If we are prefetching from the mfu ghost list, this buffer
+ * will end up on the mru list; so steal space from there.
+ */
+ if (state == arc_mfu_ghost)
+ state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
+ else if (state == arc_mru_ghost)
+ state = arc_mru;
+
+ if (state == arc_mru || state == arc_anon) {
+ uint64_t mru_used = arc_anon->arcs_size + arc_mru->arcs_size;
+ state = (arc_mfu->arcs_lsize[type] >= size &&
+ arc_p > mru_used) ? arc_mfu : arc_mru;
+ } else {
+ /* MFU cases */
+ uint64_t mfu_space = arc_c - arc_p;
+ state = (arc_mru->arcs_lsize[type] >= size &&
+ mfu_space > arc_mfu->arcs_size) ? arc_mru : arc_mfu;
+ }
+ if ((buf->b_data = arc_evict(state, NULL, size, TRUE, type)) == NULL) {
+ if (type == ARC_BUFC_METADATA) {
+ buf->b_data = zio_buf_alloc(size);
+ arc_space_consume(size, ARC_SPACE_DATA);
+ } else {
+ ASSERT(type == ARC_BUFC_DATA);
+ buf->b_data = zio_data_buf_alloc(size);
+ ARCSTAT_INCR(arcstat_data_size, size);
+ atomic_add_64(&arc_size, size);
+ }
+ ARCSTAT_BUMP(arcstat_recycle_miss);
+ }
+ ASSERT(buf->b_data != NULL);
+out:
+ /*
+ * Update the state size. Note that ghost states have a
+ * "ghost size" and so don't need to be updated.
+ */
+ if (!GHOST_STATE(buf->b_hdr->b_state)) {
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+
+ atomic_add_64(&hdr->b_state->arcs_size, size);
+ if (list_link_active(&hdr->b_arc_node)) {
+ ASSERT(refcount_is_zero(&hdr->b_refcnt));
+ atomic_add_64(&hdr->b_state->arcs_lsize[type], size);
+ }
+ /*
+ * If we are growing the cache, and we are adding anonymous
+ * data, and we have outgrown arc_p, update arc_p
+ */
+ if (arc_size < arc_c && hdr->b_state == arc_anon &&
+ arc_anon->arcs_size + arc_mru->arcs_size > arc_p)
+ arc_p = MIN(arc_c, arc_p + size);
+ }
+}
+
+/*
+ * This routine is called whenever a buffer is accessed.
+ * NOTE: the hash lock is dropped in this function.
+ */
+static void
+arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
+{
+ clock_t now;
+
+ ASSERT(MUTEX_HELD(hash_lock));
+
+ if (buf->b_state == arc_anon) {
+ /*
+ * This buffer is not in the cache, and does not
+ * appear in our "ghost" list. Add the new buffer
+ * to the MRU state.
+ */
+
+ ASSERT(buf->b_arc_access == 0);
+ buf->b_arc_access = ddi_get_lbolt();
+ DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
+ arc_change_state(arc_mru, buf, hash_lock);
+
+ } else if (buf->b_state == arc_mru) {
+ now = ddi_get_lbolt();
+
+ /*
+ * If this buffer is here because of a prefetch, then either:
+ * - clear the flag if this is a "referencing" read
+ * (any subsequent access will bump this into the MFU state).
+ * or
+ * - move the buffer to the head of the list if this is
+ * another prefetch (to make it less likely to be evicted).
+ */
+ if ((buf->b_flags & ARC_PREFETCH) != 0) {
+ if (refcount_count(&buf->b_refcnt) == 0) {
+ ASSERT(list_link_active(&buf->b_arc_node));
+ } else {
+ buf->b_flags &= ~ARC_PREFETCH;
+ ARCSTAT_BUMP(arcstat_mru_hits);
+ }
+ buf->b_arc_access = now;
+ return;
+ }
+
+ /*
+ * This buffer has been "accessed" only once so far,
+ * but it is still in the cache. Move it to the MFU
+ * state.
+ */
+ if (now > buf->b_arc_access + ARC_MINTIME) {
+ /*
+ * More than 125ms have passed since we
+ * instantiated this buffer. Move it to the
+ * most frequently used state.
+ */
+ buf->b_arc_access = now;
+ DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
+ arc_change_state(arc_mfu, buf, hash_lock);
+ }
+ ARCSTAT_BUMP(arcstat_mru_hits);
+ } else if (buf->b_state == arc_mru_ghost) {
+ arc_state_t *new_state;
+ /*
+ * This buffer has been "accessed" recently, but
+ * was evicted from the cache. Move it to the
+ * MFU state.
+ */
+
+ if (buf->b_flags & ARC_PREFETCH) {
+ new_state = arc_mru;
+ if (refcount_count(&buf->b_refcnt) > 0)
+ buf->b_flags &= ~ARC_PREFETCH;
+ DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
+ } else {
+ new_state = arc_mfu;
+ DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
+ }
+
+ buf->b_arc_access = ddi_get_lbolt();
+ arc_change_state(new_state, buf, hash_lock);
+
+ ARCSTAT_BUMP(arcstat_mru_ghost_hits);
+ } else if (buf->b_state == arc_mfu) {
+ /*
+ * This buffer has been accessed more than once and is
+ * still in the cache. Keep it in the MFU state.
+ *
+ * NOTE: an add_reference() that occurred when we did
+ * the arc_read() will have kicked this off the list.
+ * If it was a prefetch, we will explicitly move it to
+ * the head of the list now.
+ */
+ if ((buf->b_flags & ARC_PREFETCH) != 0) {
+ ASSERT(refcount_count(&buf->b_refcnt) == 0);
+ ASSERT(list_link_active(&buf->b_arc_node));
+ }
+ ARCSTAT_BUMP(arcstat_mfu_hits);
+ buf->b_arc_access = ddi_get_lbolt();
+ } else if (buf->b_state == arc_mfu_ghost) {
+ arc_state_t *new_state = arc_mfu;
+ /*
+ * This buffer has been accessed more than once but has
+ * been evicted from the cache. Move it back to the
+ * MFU state.
+ */
+
+ if (buf->b_flags & ARC_PREFETCH) {
+ /*
+ * This is a prefetch access...
+ * move this block back to the MRU state.
+ */
+ ASSERT3U(refcount_count(&buf->b_refcnt), ==, 0);
+ new_state = arc_mru;
+ }
+
+ buf->b_arc_access = ddi_get_lbolt();
+ DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
+ arc_change_state(new_state, buf, hash_lock);
+
+ ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
+ } else if (buf->b_state == arc_l2c_only) {
+ /*
+ * This buffer is on the 2nd Level ARC.
+ */
+
+ buf->b_arc_access = ddi_get_lbolt();
+ DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
+ arc_change_state(arc_mfu, buf, hash_lock);
+ } else {
+ ASSERT(!"invalid arc state");
+ }
+}
+
+/* a generic arc_done_func_t which you can use */
+/* ARGSUSED */
+void
+arc_bcopy_func(zio_t *zio, arc_buf_t *buf, void *arg)
+{
+ if (zio == NULL || zio->io_error == 0)
+ bcopy(buf->b_data, arg, buf->b_hdr->b_size);
+ VERIFY(arc_buf_remove_ref(buf, arg) == 1);
+}
+
+/* a generic arc_done_func_t */
+void
+arc_getbuf_func(zio_t *zio, arc_buf_t *buf, void *arg)
+{
+ arc_buf_t **bufp = arg;
+ if (zio && zio->io_error) {
+ VERIFY(arc_buf_remove_ref(buf, arg) == 1);
+ *bufp = NULL;
+ } else {
+ *bufp = buf;
+ ASSERT(buf->b_data);
+ }
+}
+
+static void
+arc_read_done(zio_t *zio)
+{
+ arc_buf_hdr_t *hdr, *found;
+ arc_buf_t *buf;
+ arc_buf_t *abuf; /* buffer we're assigning to callback */
+ kmutex_t *hash_lock;
+ arc_callback_t *callback_list, *acb;
+ int freeable = FALSE;
+
+ buf = zio->io_private;
+ hdr = buf->b_hdr;
+
+ /*
+ * The hdr was inserted into hash-table and removed from lists
+ * prior to starting I/O. We should find this header, since
+ * it's in the hash table, and it should be legit since it's
+ * not possible to evict it during the I/O. The only possible
+ * reason for it not to be found is if we were freed during the
+ * read.
+ */
+ found = buf_hash_find(hdr->b_spa, &hdr->b_dva, hdr->b_birth,
+ &hash_lock);
+
+ ASSERT((found == NULL && HDR_FREED_IN_READ(hdr) && hash_lock == NULL) ||
+ (found == hdr && DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
+ (found == hdr && HDR_L2_READING(hdr)));
+
+ hdr->b_flags &= ~ARC_L2_EVICTED;
+ if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
+ hdr->b_flags &= ~ARC_L2CACHE;
+
+ /* byteswap if necessary */
+ callback_list = hdr->b_acb;
+ ASSERT(callback_list != NULL);
+ if (BP_SHOULD_BYTESWAP(zio->io_bp) && zio->io_error == 0) {
+ arc_byteswap_func_t *func = BP_GET_LEVEL(zio->io_bp) > 0 ?
+ byteswap_uint64_array :
+ dmu_ot[BP_GET_TYPE(zio->io_bp)].ot_byteswap;
+ func(buf->b_data, hdr->b_size);
+ }
+
+ arc_cksum_compute(buf, B_FALSE);
+
+ if (hash_lock && zio->io_error == 0 && hdr->b_state == arc_anon) {
+ /*
+ * Only call arc_access on anonymous buffers. This is because
+ * if we've issued an I/O for an evicted buffer, we've already
+ * called arc_access (to prevent any simultaneous readers from
+ * getting confused).
+ */
+ arc_access(hdr, hash_lock);
+ }
+
+ /* create copies of the data buffer for the callers */
+ abuf = buf;
+ for (acb = callback_list; acb; acb = acb->acb_next) {
+ if (acb->acb_done) {
+ if (abuf == NULL)
+ abuf = arc_buf_clone(buf);
+ acb->acb_buf = abuf;
+ abuf = NULL;
+ }
+ }
+ hdr->b_acb = NULL;
+ hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
+ ASSERT(!HDR_BUF_AVAILABLE(hdr));
+ if (abuf == buf) {
+ ASSERT(buf->b_efunc == NULL);
+ ASSERT(hdr->b_datacnt == 1);
+ hdr->b_flags |= ARC_BUF_AVAILABLE;
+ }
+
+ ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
+
+ if (zio->io_error != 0) {
+ hdr->b_flags |= ARC_IO_ERROR;
+ if (hdr->b_state != arc_anon)
+ arc_change_state(arc_anon, hdr, hash_lock);
+ if (HDR_IN_HASH_TABLE(hdr))
+ buf_hash_remove(hdr);
+ freeable = refcount_is_zero(&hdr->b_refcnt);
+ }
+
+ /*
+ * Broadcast before we drop the hash_lock to avoid the possibility
+ * that the hdr (and hence the cv) might be freed before we get to
+ * the cv_broadcast().
+ */
+ cv_broadcast(&hdr->b_cv);
+
+ if (hash_lock) {
+ mutex_exit(hash_lock);
+ } else {
+ /*
+ * This block was freed while we waited for the read to
+ * complete. It has been removed from the hash table and
+ * moved to the anonymous state (so that it won't show up
+ * in the cache).
+ */
+ ASSERT3P(hdr->b_state, ==, arc_anon);
+ freeable = refcount_is_zero(&hdr->b_refcnt);
+ }
+
+ /* execute each callback and free its structure */
+ while ((acb = callback_list) != NULL) {
+ if (acb->acb_done)
+ acb->acb_done(zio, acb->acb_buf, acb->acb_private);
+
+ if (acb->acb_zio_dummy != NULL) {
+ acb->acb_zio_dummy->io_error = zio->io_error;
+ zio_nowait(acb->acb_zio_dummy);
+ }
+
+ callback_list = acb->acb_next;
+ kmem_free(acb, sizeof (arc_callback_t));
+ }
+
+ if (freeable)
+ arc_hdr_destroy(hdr);
+}
+
+/*
+ * "Read" the block block at the specified DVA (in bp) via the
+ * cache. If the block is found in the cache, invoke the provided
+ * callback immediately and return. Note that the `zio' parameter
+ * in the callback will be NULL in this case, since no IO was
+ * required. If the block is not in the cache pass the read request
+ * on to the spa with a substitute callback function, so that the
+ * requested block will be added to the cache.
+ *
+ * If a read request arrives for a block that has a read in-progress,
+ * either wait for the in-progress read to complete (and return the
+ * results); or, if this is a read with a "done" func, add a record
+ * to the read to invoke the "done" func when the read completes,
+ * and return; or just return.
+ *
+ * arc_read_done() will invoke all the requested "done" functions
+ * for readers of this block.
+ *
+ * Normal callers should use arc_read and pass the arc buffer and offset
+ * for the bp. But if you know you don't need locking, you can use
+ * arc_read_bp.
+ */
+int
+arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_buf_t *pbuf,
+ arc_done_func_t *done, void *private, int priority, int zio_flags,
+ uint32_t *arc_flags, const zbookmark_t *zb)
+{
+ int err;
+
+ if (pbuf == NULL) {
+ /*
+ * XXX This happens from traverse callback funcs, for
+ * the objset_phys_t block.
+ */
+ return (arc_read_nolock(pio, spa, bp, done, private, priority,
+ zio_flags, arc_flags, zb));
+ }
+
+ ASSERT(!refcount_is_zero(&pbuf->b_hdr->b_refcnt));
+ ASSERT3U((char *)bp - (char *)pbuf->b_data, <, pbuf->b_hdr->b_size);
+ rw_enter(&pbuf->b_data_lock, RW_READER);
+
+ err = arc_read_nolock(pio, spa, bp, done, private, priority,
+ zio_flags, arc_flags, zb);
+ rw_exit(&pbuf->b_data_lock);
+
+ return (err);
+}
+
+int
+arc_read_nolock(zio_t *pio, spa_t *spa, const blkptr_t *bp,
+ arc_done_func_t *done, void *private, int priority, int zio_flags,
+ uint32_t *arc_flags, const zbookmark_t *zb)
+{
+ arc_buf_hdr_t *hdr;
+ arc_buf_t *buf;
+ kmutex_t *hash_lock;
+ zio_t *rzio;
+ uint64_t guid = spa_guid(spa);
+
+top:
+ hdr = buf_hash_find(guid, BP_IDENTITY(bp), BP_PHYSICAL_BIRTH(bp),
+ &hash_lock);
+ if (hdr && hdr->b_datacnt > 0) {
+
+ *arc_flags |= ARC_CACHED;
+
+ if (HDR_IO_IN_PROGRESS(hdr)) {
+
+ if (*arc_flags & ARC_WAIT) {
+ cv_wait(&hdr->b_cv, hash_lock);
+ mutex_exit(hash_lock);
+ goto top;
+ }
+ ASSERT(*arc_flags & ARC_NOWAIT);
+
+ if (done) {
+ arc_callback_t *acb = NULL;
+
+ acb = kmem_zalloc(sizeof (arc_callback_t),
+ KM_SLEEP);
+ acb->acb_done = done;
+ acb->acb_private = private;
+ if (pio != NULL)
+ acb->acb_zio_dummy = zio_null(pio,
+ spa, NULL, NULL, NULL, zio_flags);
+
+ ASSERT(acb->acb_done != NULL);
+ acb->acb_next = hdr->b_acb;
+ hdr->b_acb = acb;
+ add_reference(hdr, hash_lock, private);
+ mutex_exit(hash_lock);
+ return (0);
+ }
+ mutex_exit(hash_lock);
+ return (0);
+ }
+
+ ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
+
+ if (done) {
+ add_reference(hdr, hash_lock, private);
+ /*
+ * If this block is already in use, create a new
+ * copy of the data so that we will be guaranteed
+ * that arc_release() will always succeed.
+ */
+ buf = hdr->b_buf;
+ ASSERT(buf);
+ ASSERT(buf->b_data);
+ if (HDR_BUF_AVAILABLE(hdr)) {
+ ASSERT(buf->b_efunc == NULL);
+ hdr->b_flags &= ~ARC_BUF_AVAILABLE;
+ } else {
+ buf = arc_buf_clone(buf);
+ }
+
+ } else if (*arc_flags & ARC_PREFETCH &&
+ refcount_count(&hdr->b_refcnt) == 0) {
+ hdr->b_flags |= ARC_PREFETCH;
+ }
+ DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
+ arc_access(hdr, hash_lock);
+ if (*arc_flags & ARC_L2CACHE)
+ hdr->b_flags |= ARC_L2CACHE;
+ mutex_exit(hash_lock);
+ ARCSTAT_BUMP(arcstat_hits);
+ ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
+ demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
+ data, metadata, hits);
+
+ if (done)
+ done(NULL, buf, private);
+ } else {
+ uint64_t size = BP_GET_LSIZE(bp);
+ arc_callback_t *acb;
+ vdev_t *vd = NULL;
+ uint64_t addr;
+ boolean_t devw = B_FALSE;
+
+ if (hdr == NULL) {
+ /* this block is not in the cache */
+ arc_buf_hdr_t *exists;
+ arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
+ buf = arc_buf_alloc(spa, size, private, type);
+ hdr = buf->b_hdr;
+ hdr->b_dva = *BP_IDENTITY(bp);
+ hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
+ hdr->b_cksum0 = bp->blk_cksum.zc_word[0];
+ exists = buf_hash_insert(hdr, &hash_lock);
+ if (exists) {
+ /* somebody beat us to the hash insert */
+ mutex_exit(hash_lock);
+ buf_discard_identity(hdr);
+ (void) arc_buf_remove_ref(buf, private);
+ goto top; /* restart the IO request */
+ }
+ /* if this is a prefetch, we don't have a reference */
+ if (*arc_flags & ARC_PREFETCH) {
+ (void) remove_reference(hdr, hash_lock,
+ private);
+ hdr->b_flags |= ARC_PREFETCH;
+ }
+ if (*arc_flags & ARC_L2CACHE)
+ hdr->b_flags |= ARC_L2CACHE;
+ if (BP_GET_LEVEL(bp) > 0)
+ hdr->b_flags |= ARC_INDIRECT;
+ } else {
+ /* this block is in the ghost cache */
+ ASSERT(GHOST_STATE(hdr->b_state));
+ ASSERT(!HDR_IO_IN_PROGRESS(hdr));
+ ASSERT3U(refcount_count(&hdr->b_refcnt), ==, 0);
+ ASSERT(hdr->b_buf == NULL);
+
+ /* if this is a prefetch, we don't have a reference */
+ if (*arc_flags & ARC_PREFETCH)
+ hdr->b_flags |= ARC_PREFETCH;
+ else
+ add_reference(hdr, hash_lock, private);
+ if (*arc_flags & ARC_L2CACHE)
+ hdr->b_flags |= ARC_L2CACHE;
+ buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
+ buf->b_hdr = hdr;
+ buf->b_data = NULL;
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+ buf->b_next = NULL;
+ hdr->b_buf = buf;
+ ASSERT(hdr->b_datacnt == 0);
+ hdr->b_datacnt = 1;
+ arc_get_data_buf(buf);
+ arc_access(hdr, hash_lock);
+ }
+
+ ASSERT(!GHOST_STATE(hdr->b_state));
+
+ acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
+ acb->acb_done = done;
+ acb->acb_private = private;
+
+ ASSERT(hdr->b_acb == NULL);
+ hdr->b_acb = acb;
+ hdr->b_flags |= ARC_IO_IN_PROGRESS;
+
+ if (HDR_L2CACHE(hdr) && hdr->b_l2hdr != NULL &&
+ (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
+ devw = hdr->b_l2hdr->b_dev->l2ad_writing;
+ addr = hdr->b_l2hdr->b_daddr;
+ /*
+ * Lock out device removal.
+ */
+ if (vdev_is_dead(vd) ||
+ !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
+ vd = NULL;
+ }
+
+ mutex_exit(hash_lock);
+
+ ASSERT3U(hdr->b_size, ==, size);
+ DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
+ uint64_t, size, zbookmark_t *, zb);
+ ARCSTAT_BUMP(arcstat_misses);
+ ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
+ demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
+ data, metadata, misses);
+
+ if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
+ /*
+ * Read from the L2ARC if the following are true:
+ * 1. The L2ARC vdev was previously cached.
+ * 2. This buffer still has L2ARC metadata.
+ * 3. This buffer isn't currently writing to the L2ARC.
+ * 4. The L2ARC entry wasn't evicted, which may
+ * also have invalidated the vdev.
+ * 5. This isn't prefetch and l2arc_noprefetch is set.
+ */
+ if (hdr->b_l2hdr != NULL &&
+ !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
+ !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
+ l2arc_read_callback_t *cb;
+
+ DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
+ ARCSTAT_BUMP(arcstat_l2_hits);
+
+ cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
+ KM_SLEEP);
+ cb->l2rcb_buf = buf;
+ cb->l2rcb_spa = spa;
+ cb->l2rcb_bp = *bp;
+ cb->l2rcb_zb = *zb;
+ cb->l2rcb_flags = zio_flags;
+
+ /*
+ * l2arc read. The SCL_L2ARC lock will be
+ * released by l2arc_read_done().
+ */
+ rzio = zio_read_phys(pio, vd, addr, size,
+ buf->b_data, ZIO_CHECKSUM_OFF,
+ l2arc_read_done, cb, priority, zio_flags |
+ ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
+ ZIO_FLAG_DONT_PROPAGATE |
+ ZIO_FLAG_DONT_RETRY, B_FALSE);
+ DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
+ zio_t *, rzio);
+ ARCSTAT_INCR(arcstat_l2_read_bytes, size);
+
+ if (*arc_flags & ARC_NOWAIT) {
+ zio_nowait(rzio);
+ return (0);
+ }
+
+ ASSERT(*arc_flags & ARC_WAIT);
+ if (zio_wait(rzio) == 0)
+ return (0);
+
+ /* l2arc read error; goto zio_read() */
+ } else {
+ DTRACE_PROBE1(l2arc__miss,
+ arc_buf_hdr_t *, hdr);
+ ARCSTAT_BUMP(arcstat_l2_misses);
+ if (HDR_L2_WRITING(hdr))
+ ARCSTAT_BUMP(arcstat_l2_rw_clash);
+ spa_config_exit(spa, SCL_L2ARC, vd);
+ }
+ } else {
+ if (vd != NULL)
+ spa_config_exit(spa, SCL_L2ARC, vd);
+ if (l2arc_ndev != 0) {
+ DTRACE_PROBE1(l2arc__miss,
+ arc_buf_hdr_t *, hdr);
+ ARCSTAT_BUMP(arcstat_l2_misses);
+ }
+ }
+
+ rzio = zio_read(pio, spa, bp, buf->b_data, size,
+ arc_read_done, buf, priority, zio_flags, zb);
+
+ if (*arc_flags & ARC_WAIT)
+ return (zio_wait(rzio));
+
+ ASSERT(*arc_flags & ARC_NOWAIT);
+ zio_nowait(rzio);
+ }
+ return (0);
+}
+
+void
+arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
+{
+ ASSERT(buf->b_hdr != NULL);
+ ASSERT(buf->b_hdr->b_state != arc_anon);
+ ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
+ ASSERT(buf->b_efunc == NULL);
+ ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
+
+ buf->b_efunc = func;
+ buf->b_private = private;
+}
+
+/*
+ * This is used by the DMU to let the ARC know that a buffer is
+ * being evicted, so the ARC should clean up. If this arc buf
+ * is not yet in the evicted state, it will be put there.
+ */
+int
+arc_buf_evict(arc_buf_t *buf)
+{
+ arc_buf_hdr_t *hdr;
+ kmutex_t *hash_lock;
+ arc_buf_t **bufp;
+
+ mutex_enter(&buf->b_evict_lock);
+ hdr = buf->b_hdr;
+ if (hdr == NULL) {
+ /*
+ * We are in arc_do_user_evicts().
+ */
+ ASSERT(buf->b_data == NULL);
+ mutex_exit(&buf->b_evict_lock);
+ return (0);
+ } else if (buf->b_data == NULL) {
+ arc_buf_t copy = *buf; /* structure assignment */
+ /*
+ * We are on the eviction list; process this buffer now
+ * but let arc_do_user_evicts() do the reaping.
+ */
+ buf->b_efunc = NULL;
+ mutex_exit(&buf->b_evict_lock);
+ VERIFY(copy.b_efunc(&copy) == 0);
+ return (1);
+ }
+ hash_lock = HDR_LOCK(hdr);
+ mutex_enter(hash_lock);
+ hdr = buf->b_hdr;
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+
+ ASSERT3U(refcount_count(&hdr->b_refcnt), <, hdr->b_datacnt);
+ ASSERT(hdr->b_state == arc_mru || hdr->b_state == arc_mfu);
+
+ /*
+ * Pull this buffer off of the hdr
+ */
+ bufp = &hdr->b_buf;
+ while (*bufp != buf)
+ bufp = &(*bufp)->b_next;
+ *bufp = buf->b_next;
+
+ ASSERT(buf->b_data != NULL);
+ arc_buf_destroy(buf, FALSE, FALSE);
+
+ if (hdr->b_datacnt == 0) {
+ arc_state_t *old_state = hdr->b_state;
+ arc_state_t *evicted_state;
+
+ ASSERT(hdr->b_buf == NULL);
+ ASSERT(refcount_is_zero(&hdr->b_refcnt));
+
+ evicted_state =
+ (old_state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
+
+ mutex_enter(&old_state->arcs_mtx);
+ mutex_enter(&evicted_state->arcs_mtx);
+
+ arc_change_state(evicted_state, hdr, hash_lock);
+ ASSERT(HDR_IN_HASH_TABLE(hdr));
+ hdr->b_flags |= ARC_IN_HASH_TABLE;
+ hdr->b_flags &= ~ARC_BUF_AVAILABLE;
+
+ mutex_exit(&evicted_state->arcs_mtx);
+ mutex_exit(&old_state->arcs_mtx);
+ }
+ mutex_exit(hash_lock);
+ mutex_exit(&buf->b_evict_lock);
+
+ VERIFY(buf->b_efunc(buf) == 0);
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+ buf->b_hdr = NULL;
+ buf->b_next = NULL;
+ kmem_cache_free(buf_cache, buf);
+ return (1);
+}
+
+/*
+ * Release this buffer from the cache. This must be done
+ * after a read and prior to modifying the buffer contents.
+ * If the buffer has more than one reference, we must make
+ * a new hdr for the buffer.
+ */
+void
+arc_release(arc_buf_t *buf, void *tag)
+{
+ arc_buf_hdr_t *hdr;
+ kmutex_t *hash_lock = NULL;
+ l2arc_buf_hdr_t *l2hdr;
+ uint64_t buf_size;
+
+ /*
+ * It would be nice to assert that if it's DMU metadata (level >
+ * 0 || it's the dnode file), then it must be syncing context.
+ * But we don't know that information at this level.
+ */
+
+ mutex_enter(&buf->b_evict_lock);
+ hdr = buf->b_hdr;
+
+ /* this buffer is not on any list */
+ ASSERT(refcount_count(&hdr->b_refcnt) > 0);
+
+ if (hdr->b_state == arc_anon) {
+ /* this buffer is already released */
+ ASSERT(buf->b_efunc == NULL);
+ } else {
+ hash_lock = HDR_LOCK(hdr);
+ mutex_enter(hash_lock);
+ hdr = buf->b_hdr;
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+ }
+
+ l2hdr = hdr->b_l2hdr;
+ if (l2hdr) {
+ mutex_enter(&l2arc_buflist_mtx);
+ hdr->b_l2hdr = NULL;
+ buf_size = hdr->b_size;
+ }
+
+ /*
+ * Do we have more than one buf?
+ */
+ if (hdr->b_datacnt > 1) {
+ arc_buf_hdr_t *nhdr;
+ arc_buf_t **bufp;
+ uint64_t blksz = hdr->b_size;
+ uint64_t spa = hdr->b_spa;
+ arc_buf_contents_t type = hdr->b_type;
+ uint32_t flags = hdr->b_flags;
+
+ ASSERT(hdr->b_buf != buf || buf->b_next != NULL);
+ /*
+ * Pull the data off of this hdr and attach it to
+ * a new anonymous hdr.
+ */
+ (void) remove_reference(hdr, hash_lock, tag);
+ bufp = &hdr->b_buf;
+ while (*bufp != buf)
+ bufp = &(*bufp)->b_next;
+ *bufp = buf->b_next;
+ buf->b_next = NULL;
+
+ ASSERT3U(hdr->b_state->arcs_size, >=, hdr->b_size);
+ atomic_add_64(&hdr->b_state->arcs_size, -hdr->b_size);
+ if (refcount_is_zero(&hdr->b_refcnt)) {
+ uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
+ ASSERT3U(*size, >=, hdr->b_size);
+ atomic_add_64(size, -hdr->b_size);
+ }
+ hdr->b_datacnt -= 1;
+ arc_cksum_verify(buf);
+
+ mutex_exit(hash_lock);
+
+ nhdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
+ nhdr->b_size = blksz;
+ nhdr->b_spa = spa;
+ nhdr->b_type = type;
+ nhdr->b_buf = buf;
+ nhdr->b_state = arc_anon;
+ nhdr->b_arc_access = 0;
+ nhdr->b_flags = flags & ARC_L2_WRITING;
+ nhdr->b_l2hdr = NULL;
+ nhdr->b_datacnt = 1;
+ nhdr->b_freeze_cksum = NULL;
+ (void) refcount_add(&nhdr->b_refcnt, tag);
+ buf->b_hdr = nhdr;
+ mutex_exit(&buf->b_evict_lock);
+ atomic_add_64(&arc_anon->arcs_size, blksz);
+ } else {
+ mutex_exit(&buf->b_evict_lock);
+ ASSERT(refcount_count(&hdr->b_refcnt) == 1);
+ ASSERT(!list_link_active(&hdr->b_arc_node));
+ ASSERT(!HDR_IO_IN_PROGRESS(hdr));
+ if (hdr->b_state != arc_anon)
+ arc_change_state(arc_anon, hdr, hash_lock);
+ hdr->b_arc_access = 0;
+ if (hash_lock)
+ mutex_exit(hash_lock);
+
+ buf_discard_identity(hdr);
+ arc_buf_thaw(buf);
+ }
+ buf->b_efunc = NULL;
+ buf->b_private = NULL;
+
+ if (l2hdr) {
+ list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
+ kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
+ ARCSTAT_INCR(arcstat_l2_size, -buf_size);
+ mutex_exit(&l2arc_buflist_mtx);
+ }
+}
+
+/*
+ * Release this buffer. If it does not match the provided BP, fill it
+ * with that block's contents.
+ */
+/* ARGSUSED */
+int
+arc_release_bp(arc_buf_t *buf, void *tag, blkptr_t *bp, spa_t *spa,
+ zbookmark_t *zb)
+{
+ arc_release(buf, tag);
+ return (0);
+}
+
+int
+arc_released(arc_buf_t *buf)
+{
+ int released;
+
+ mutex_enter(&buf->b_evict_lock);
+ released = (buf->b_data != NULL && buf->b_hdr->b_state == arc_anon);
+ mutex_exit(&buf->b_evict_lock);
+ return (released);
+}
+
+int
+arc_has_callback(arc_buf_t *buf)
+{
+ int callback;
+
+ mutex_enter(&buf->b_evict_lock);
+ callback = (buf->b_efunc != NULL);
+ mutex_exit(&buf->b_evict_lock);
+ return (callback);
+}
+
+#ifdef ZFS_DEBUG
+int
+arc_referenced(arc_buf_t *buf)
+{
+ int referenced;
+
+ mutex_enter(&buf->b_evict_lock);
+ referenced = (refcount_count(&buf->b_hdr->b_refcnt));
+ mutex_exit(&buf->b_evict_lock);
+ return (referenced);
+}
+#endif
+
+static void
+arc_write_ready(zio_t *zio)
+{
+ arc_write_callback_t *callback = zio->io_private;
+ arc_buf_t *buf = callback->awcb_buf;
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+
+ ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt));
+ callback->awcb_ready(zio, buf, callback->awcb_private);
+
+ /*
+ * If the IO is already in progress, then this is a re-write
+ * attempt, so we need to thaw and re-compute the cksum.
+ * It is the responsibility of the callback to handle the
+ * accounting for any re-write attempt.
+ */
+ if (HDR_IO_IN_PROGRESS(hdr)) {
+ mutex_enter(&hdr->b_freeze_lock);
+ if (hdr->b_freeze_cksum != NULL) {
+ kmem_free(hdr->b_freeze_cksum, sizeof (zio_cksum_t));
+ hdr->b_freeze_cksum = NULL;
+ }
+ mutex_exit(&hdr->b_freeze_lock);
+ }
+ arc_cksum_compute(buf, B_FALSE);
+ hdr->b_flags |= ARC_IO_IN_PROGRESS;
+}
+
+static void
+arc_write_done(zio_t *zio)
+{
+ arc_write_callback_t *callback = zio->io_private;
+ arc_buf_t *buf = callback->awcb_buf;
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+
+ ASSERT(hdr->b_acb == NULL);
+
+ if (zio->io_error == 0) {
+ hdr->b_dva = *BP_IDENTITY(zio->io_bp);
+ hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
+ hdr->b_cksum0 = zio->io_bp->blk_cksum.zc_word[0];
+ } else {
+ ASSERT(BUF_EMPTY(hdr));
+ }
+
+ /*
+ * If the block to be written was all-zero, we may have
+ * compressed it away. In this case no write was performed
+ * so there will be no dva/birth/checksum. The buffer must
+ * therefore remain anonymous (and uncached).
+ */
+ if (!BUF_EMPTY(hdr)) {
+ arc_buf_hdr_t *exists;
+ kmutex_t *hash_lock;
+
+ ASSERT(zio->io_error == 0);
+
+ arc_cksum_verify(buf);
+
+ exists = buf_hash_insert(hdr, &hash_lock);
+ if (exists) {
+ /*
+ * This can only happen if we overwrite for
+ * sync-to-convergence, because we remove
+ * buffers from the hash table when we arc_free().
+ */
+ if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
+ if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
+ panic("bad overwrite, hdr=%p exists=%p",
+ (void *)hdr, (void *)exists);
+ ASSERT(refcount_is_zero(&exists->b_refcnt));
+ arc_change_state(arc_anon, exists, hash_lock);
+ mutex_exit(hash_lock);
+ arc_hdr_destroy(exists);
+ exists = buf_hash_insert(hdr, &hash_lock);
+ ASSERT3P(exists, ==, NULL);
+ } else {
+ /* Dedup */
+ ASSERT(hdr->b_datacnt == 1);
+ ASSERT(hdr->b_state == arc_anon);
+ ASSERT(BP_GET_DEDUP(zio->io_bp));
+ ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
+ }
+ }
+ hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
+ /* if it's not anon, we are doing a scrub */
+ if (!exists && hdr->b_state == arc_anon)
+ arc_access(hdr, hash_lock);
+ mutex_exit(hash_lock);
+ } else {
+ hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
+ }
+
+ ASSERT(!refcount_is_zero(&hdr->b_refcnt));
+ callback->awcb_done(zio, buf, callback->awcb_private);
+
+ kmem_free(callback, sizeof (arc_write_callback_t));
+}
+
+zio_t *
+arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
+ blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, const zio_prop_t *zp,
+ arc_done_func_t *ready, arc_done_func_t *done, void *private,
+ int priority, int zio_flags, const zbookmark_t *zb)
+{
+ arc_buf_hdr_t *hdr = buf->b_hdr;
+ arc_write_callback_t *callback;
+ zio_t *zio;
+
+ ASSERT(ready != NULL);
+ ASSERT(done != NULL);
+ ASSERT(!HDR_IO_ERROR(hdr));
+ ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
+ ASSERT(hdr->b_acb == NULL);
+ if (l2arc)
+ hdr->b_flags |= ARC_L2CACHE;
+ callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
+ callback->awcb_ready = ready;
+ callback->awcb_done = done;
+ callback->awcb_private = private;
+ callback->awcb_buf = buf;
+
+ zio = zio_write(pio, spa, txg, bp, buf->b_data, hdr->b_size, zp,
+ arc_write_ready, arc_write_done, callback, priority, zio_flags, zb);
+
+ return (zio);
+}
+
+static int
+arc_memory_throttle(uint64_t reserve, uint64_t inflight_data, uint64_t txg)
+{
+#ifdef _KERNEL
+ uint64_t available_memory = ptob(freemem);
+ static uint64_t page_load = 0;
+ static uint64_t last_txg = 0;
+
+#if defined(__i386)
+ available_memory =
+ MIN(available_memory, vmem_size(heap_arena, VMEM_FREE));
+#endif
+ if (available_memory >= zfs_write_limit_max)
+ return (0);
+
+ if (txg > last_txg) {
+ last_txg = txg;
+ page_load = 0;
+ }
+ /*
+ * If we are in pageout, we know that memory is already tight,
+ * the arc is already going to be evicting, so we just want to
+ * continue to let page writes occur as quickly as possible.
+ */
+ if (curproc == proc_pageout) {
+ if (page_load > MAX(ptob(minfree), available_memory) / 4)
+ return (ERESTART);
+ /* Note: reserve is inflated, so we deflate */
+ page_load += reserve / 8;
+ return (0);
+ } else if (page_load > 0 && arc_reclaim_needed()) {
+ /* memory is low, delay before restarting */
+ ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
+ return (EAGAIN);
+ }
+ page_load = 0;
+
+ if (arc_size > arc_c_min) {
+ uint64_t evictable_memory =
+ arc_mru->arcs_lsize[ARC_BUFC_DATA] +
+ arc_mru->arcs_lsize[ARC_BUFC_METADATA] +
+ arc_mfu->arcs_lsize[ARC_BUFC_DATA] +
+ arc_mfu->arcs_lsize[ARC_BUFC_METADATA];
+ available_memory += MIN(evictable_memory, arc_size - arc_c_min);
+ }
+
+ if (inflight_data > available_memory / 4) {
+ ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
+ return (ERESTART);
+ }
+#endif
+ return (0);
+}
+
+void
+arc_tempreserve_clear(uint64_t reserve)
+{
+ atomic_add_64(&arc_tempreserve, -reserve);
+ ASSERT((int64_t)arc_tempreserve >= 0);
+}
+
+int
+arc_tempreserve_space(uint64_t reserve, uint64_t txg)
+{
+ int error;
+ uint64_t anon_size;
+
+#ifdef ZFS_DEBUG
+ /*
+ * Once in a while, fail for no reason. Everything should cope.
+ */
+ if (spa_get_random(10000) == 0) {
+ dprintf("forcing random failure\n");
+ return (ERESTART);
+ }
+#endif
+ if (reserve > arc_c/4 && !arc_no_grow)
+ arc_c = MIN(arc_c_max, reserve * 4);
+ if (reserve > arc_c)
+ return (ENOMEM);
+
+ /*
+ * Don't count loaned bufs as in flight dirty data to prevent long
+ * network delays from blocking transactions that are ready to be
+ * assigned to a txg.
+ */
+ anon_size = MAX((int64_t)(arc_anon->arcs_size - arc_loaned_bytes), 0);
+
+ /*
+ * Writes will, almost always, require additional memory allocations
+ * in order to compress/encrypt/etc the data. We therefor need to
+ * make sure that there is sufficient available memory for this.
+ */
+ if (error = arc_memory_throttle(reserve, anon_size, txg))
+ return (error);
+
+ /*
+ * Throttle writes when the amount of dirty data in the cache
+ * gets too large. We try to keep the cache less than half full
+ * of dirty blocks so that our sync times don't grow too large.
+ * Note: if two requests come in concurrently, we might let them
+ * both succeed, when one of them should fail. Not a huge deal.
+ */
+
+ if (reserve + arc_tempreserve + anon_size > arc_c / 2 &&
+ anon_size > arc_c / 4) {
+ dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
+ "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
+ arc_tempreserve>>10,
+ arc_anon->arcs_lsize[ARC_BUFC_METADATA]>>10,
+ arc_anon->arcs_lsize[ARC_BUFC_DATA]>>10,
+ reserve>>10, arc_c>>10);
+ return (ERESTART);
+ }
+ atomic_add_64(&arc_tempreserve, reserve);
+ return (0);
+}
+
+void
+arc_init(void)
+{
+ mutex_init(&arc_reclaim_thr_lock, NULL, MUTEX_DEFAULT, NULL);
+ cv_init(&arc_reclaim_thr_cv, NULL, CV_DEFAULT, NULL);
+
+ /* Convert seconds to clock ticks */
+ arc_min_prefetch_lifespan = 1 * hz;
+
+ /* Start out with 1/8 of all memory */
+ arc_c = physmem * PAGESIZE / 8;
+
+#ifdef _KERNEL
+ /*
+ * On architectures where the physical memory can be larger
+ * than the addressable space (intel in 32-bit mode), we may
+ * need to limit the cache to 1/8 of VM size.
+ */
+ arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
+#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);
+
+ /*
+ * Allow the tunables to override our calculations if they are
+ * reasonable (ie. over 64MB)
+ */
+ if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE)
+ arc_c_max = zfs_arc_max;
+ if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max)
+ arc_c_min = zfs_arc_min;
+
+ arc_c = arc_c_max;
+ arc_p = (arc_c >> 1);
+
+ /* limit meta-data to 1/4 of the arc capacity */
+ arc_meta_limit = arc_c_max / 4;
+
+ /* Allow the tunable to override if it is reasonable */
+ if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
+ arc_meta_limit = zfs_arc_meta_limit;
+
+ if (arc_c_min < arc_meta_limit / 2 && zfs_arc_min == 0)
+ arc_c_min = arc_meta_limit / 2;
+
+ if (zfs_arc_grow_retry > 0)
+ arc_grow_retry = zfs_arc_grow_retry;
+
+ if (zfs_arc_shrink_shift > 0)
+ arc_shrink_shift = zfs_arc_shrink_shift;
+
+ if (zfs_arc_p_min_shift > 0)
+ arc_p_min_shift = zfs_arc_p_min_shift;
+
+ /* if kmem_flags are set, lets try to use less memory */
+ if (kmem_debugging())
+ arc_c = arc_c / 2;
+ if (arc_c < arc_c_min)
+ arc_c = arc_c_min;
+
+ arc_anon = &ARC_anon;
+ arc_mru = &ARC_mru;
+ arc_mru_ghost = &ARC_mru_ghost;
+ arc_mfu = &ARC_mfu;
+ arc_mfu_ghost = &ARC_mfu_ghost;
+ arc_l2c_only = &ARC_l2c_only;
+ arc_size = 0;
+
+ mutex_init(&arc_anon->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
+ mutex_init(&arc_mru->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
+ mutex_init(&arc_mru_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
+ mutex_init(&arc_mfu->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
+ mutex_init(&arc_mfu_ghost->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
+ mutex_init(&arc_l2c_only->arcs_mtx, NULL, MUTEX_DEFAULT, NULL);
+
+ list_create(&arc_mru->arcs_list[ARC_BUFC_METADATA],
+ sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
+ list_create(&arc_mru->arcs_list[ARC_BUFC_DATA],
+ sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
+ list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA],
+ sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
+ list_create(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA],
+ sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
+ list_create(&arc_mfu->arcs_list[ARC_BUFC_METADATA],
+ sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
+ list_create(&arc_mfu->arcs_list[ARC_BUFC_DATA],
+ sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
+ list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA],
+ sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
+ list_create(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA],
+ sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
+ list_create(&arc_l2c_only->arcs_list[ARC_BUFC_METADATA],
+ sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
+ list_create(&arc_l2c_only->arcs_list[ARC_BUFC_DATA],
+ sizeof (arc_buf_hdr_t), offsetof(arc_buf_hdr_t, b_arc_node));
+
+ buf_init();
+
+ arc_thread_exit = 0;
+ arc_eviction_list = NULL;
+ mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
+ bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
+
+ arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
+ sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
+
+ if (arc_ksp != NULL) {
+ arc_ksp->ks_data = &arc_stats;
+ kstat_install(arc_ksp);
+ }
+
+ (void) thread_create(NULL, 0, arc_reclaim_thread, NULL, 0, &p0,
+ TS_RUN, minclsyspri);
+
+ arc_dead = FALSE;
+ arc_warm = B_FALSE;
+
+ if (zfs_write_limit_max == 0)
+ zfs_write_limit_max = ptob(physmem) >> zfs_write_limit_shift;
+ else
+ zfs_write_limit_shift = 0;
+ mutex_init(&zfs_write_limit_lock, NULL, MUTEX_DEFAULT, NULL);
+}
+
+void
+arc_fini(void)
+{
+ 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(NULL);
+
+ arc_dead = TRUE;
+
+ if (arc_ksp != NULL) {
+ kstat_delete(arc_ksp);
+ arc_ksp = NULL;
+ }
+
+ mutex_destroy(&arc_eviction_mtx);
+ mutex_destroy(&arc_reclaim_thr_lock);
+ cv_destroy(&arc_reclaim_thr_cv);
+
+ list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
+ list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
+ list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
+ list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
+ list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
+ list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
+ list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
+ list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
+
+ mutex_destroy(&arc_anon->arcs_mtx);
+ mutex_destroy(&arc_mru->arcs_mtx);
+ mutex_destroy(&arc_mru_ghost->arcs_mtx);
+ mutex_destroy(&arc_mfu->arcs_mtx);
+ mutex_destroy(&arc_mfu_ghost->arcs_mtx);
+ mutex_destroy(&arc_l2c_only->arcs_mtx);
+
+ mutex_destroy(&zfs_write_limit_lock);
+
+ buf_fini();
+
+ ASSERT(arc_loaned_bytes == 0);
+}
+
+/*
+ * Level 2 ARC
+ *
+ * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
+ * It uses dedicated storage devices to hold cached data, which are populated
+ * using large infrequent writes. The main role of this cache is to boost
+ * the performance of random read workloads. The intended L2ARC devices
+ * include short-stroked disks, solid state disks, and other media with
+ * substantially faster read latency than disk.
+ *
+ * +-----------------------+
+ * | ARC |
+ * +-----------------------+
+ * | ^ ^
+ * | | |
+ * l2arc_feed_thread() arc_read()
+ * | | |
+ * | l2arc read |
+ * V | |
+ * +---------------+ |
+ * | L2ARC | |
+ * +---------------+ |
+ * | ^ |
+ * l2arc_write() | |
+ * | | |
+ * V | |
+ * +-------+ +-------+
+ * | vdev | | vdev |
+ * | cache | | cache |
+ * +-------+ +-------+
+ * +=========+ .-----.
+ * : L2ARC : |-_____-|
+ * : devices : | Disks |
+ * +=========+ `-_____-'
+ *
+ * Read requests are satisfied from the following sources, in order:
+ *
+ * 1) ARC
+ * 2) vdev cache of L2ARC devices
+ * 3) L2ARC devices
+ * 4) vdev cache of disks
+ * 5) disks
+ *
+ * Some L2ARC device types exhibit extremely slow write performance.
+ * To accommodate for this there are some significant differences between
+ * the L2ARC and traditional cache design:
+ *
+ * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
+ * the ARC behave as usual, freeing buffers and placing headers on ghost
+ * lists. The ARC does not send buffers to the L2ARC during eviction as
+ * this would add inflated write latencies for all ARC memory pressure.
+ *
+ * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
+ * It does this by periodically scanning buffers from the eviction-end of
+ * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
+ * not already there. It scans until a headroom of buffers is satisfied,
+ * which itself is a buffer for ARC eviction. The thread that does this is
+ * l2arc_feed_thread(), illustrated below; example sizes are included to
+ * provide a better sense of ratio than this diagram:
+ *
+ * head --> tail
+ * +---------------------+----------+
+ * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
+ * +---------------------+----------+ | o L2ARC eligible
+ * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
+ * +---------------------+----------+ |
+ * 15.9 Gbytes ^ 32 Mbytes |
+ * headroom |
+ * l2arc_feed_thread()
+ * |
+ * l2arc write hand <--[oooo]--'
+ * | 8 Mbyte
+ * | write max
+ * V
+ * +==============================+
+ * L2ARC dev |####|#|###|###| |####| ... |
+ * +==============================+
+ * 32 Gbytes
+ *
+ * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
+ * evicted, then the L2ARC has cached a buffer much sooner than it probably
+ * needed to, potentially wasting L2ARC device bandwidth and storage. It is
+ * safe to say that this is an uncommon case, since buffers at the end of
+ * the ARC lists have moved there due to inactivity.
+ *
+ * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
+ * then the L2ARC simply misses copying some buffers. This serves as a
+ * pressure valve to prevent heavy read workloads from both stalling the ARC
+ * with waits and clogging the L2ARC with writes. This also helps prevent
+ * the potential for the L2ARC to churn if it attempts to cache content too
+ * quickly, such as during backups of the entire pool.
+ *
+ * 5. After system boot and before the ARC has filled main memory, there are
+ * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
+ * lists can remain mostly static. Instead of searching from tail of these
+ * lists as pictured, the l2arc_feed_thread() will search from the list heads
+ * for eligible buffers, greatly increasing its chance of finding them.
+ *
+ * The L2ARC device write speed is also boosted during this time so that
+ * the L2ARC warms up faster. Since there have been no ARC evictions yet,
+ * there are no L2ARC reads, and no fear of degrading read performance
+ * through increased writes.
+ *
+ * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
+ * the vdev queue can aggregate them into larger and fewer writes. Each
+ * device is written to in a rotor fashion, sweeping writes through
+ * available space then repeating.
+ *
+ * 7. The L2ARC does not store dirty content. It never needs to flush
+ * write buffers back to disk based storage.
+ *
+ * 8. If an ARC buffer is written (and dirtied) which also exists in the
+ * L2ARC, the now stale L2ARC buffer is immediately dropped.
+ *
+ * The performance of the L2ARC can be tweaked by a number of tunables, which
+ * may be necessary for different workloads:
+ *
+ * l2arc_write_max max write bytes per interval
+ * l2arc_write_boost extra write bytes during device warmup
+ * l2arc_noprefetch skip caching prefetched buffers
+ * l2arc_headroom number of max device writes to precache
+ * l2arc_feed_secs seconds between L2ARC writing
+ *
+ * Tunables may be removed or added as future performance improvements are
+ * integrated, and also may become zpool properties.
+ *
+ * There are three key functions that control how the L2ARC warms up:
+ *
+ * l2arc_write_eligible() check if a buffer is eligible to cache
+ * l2arc_write_size() calculate how much to write
+ * l2arc_write_interval() calculate sleep delay between writes
+ *
+ * These three functions determine what to write, how much, and how quickly
+ * to send writes.
+ */
+
+static boolean_t
+l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
+{
+ /*
+ * A buffer is *not* eligible for the L2ARC if it:
+ * 1. belongs to a different spa.
+ * 2. is already cached on the L2ARC.
+ * 3. has an I/O in progress (it may be an incomplete read).
+ * 4. is flagged not eligible (zfs property).
+ */
+ if (ab->b_spa != spa_guid || ab->b_l2hdr != NULL ||
+ HDR_IO_IN_PROGRESS(ab) || !HDR_L2CACHE(ab))
+ return (B_FALSE);
+
+ return (B_TRUE);
+}
+
+static uint64_t
+l2arc_write_size(l2arc_dev_t *dev)
+{
+ uint64_t size;
+
+ size = dev->l2ad_write;
+
+ if (arc_warm == B_FALSE)
+ size += dev->l2ad_boost;
+
+ return (size);
+
+}
+
+static clock_t
+l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
+{
+ clock_t interval, next, now;
+
+ /*
+ * If the ARC lists are busy, increase our write rate; if the
+ * lists are stale, idle back. This is achieved by checking
+ * how much we previously wrote - if it was more than half of
+ * what we wanted, schedule the next write much sooner.
+ */
+ if (l2arc_feed_again && wrote > (wanted / 2))
+ interval = (hz * l2arc_feed_min_ms) / 1000;
+ else
+ interval = hz * l2arc_feed_secs;
+
+ now = ddi_get_lbolt();
+ next = MAX(now, MIN(now + interval, began + interval));
+
+ return (next);
+}
+
+static void
+l2arc_hdr_stat_add(void)
+{
+ ARCSTAT_INCR(arcstat_l2_hdr_size, HDR_SIZE + L2HDR_SIZE);
+ ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
+}
+
+static void
+l2arc_hdr_stat_remove(void)
+{
+ ARCSTAT_INCR(arcstat_l2_hdr_size, -(HDR_SIZE + L2HDR_SIZE));
+ ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
+}
+
+/*
+ * Cycle through L2ARC devices. This is how L2ARC load balances.
+ * If a device is returned, this also returns holding the spa config lock.
+ */
+static l2arc_dev_t *
+l2arc_dev_get_next(void)
+{
+ l2arc_dev_t *first, *next = NULL;
+
+ /*
+ * Lock out the removal of spas (spa_namespace_lock), then removal
+ * of cache devices (l2arc_dev_mtx). Once a device has been selected,
+ * both locks will be dropped and a spa config lock held instead.
+ */
+ mutex_enter(&spa_namespace_lock);
+ mutex_enter(&l2arc_dev_mtx);
+
+ /* if there are no vdevs, there is nothing to do */
+ if (l2arc_ndev == 0)
+ goto out;
+
+ first = NULL;
+ next = l2arc_dev_last;
+ do {
+ /* loop around the list looking for a non-faulted vdev */
+ if (next == NULL) {
+ next = list_head(l2arc_dev_list);
+ } else {
+ next = list_next(l2arc_dev_list, next);
+ if (next == NULL)
+ next = list_head(l2arc_dev_list);
+ }
+
+ /* if we have come back to the start, bail out */
+ if (first == NULL)
+ first = next;
+ else if (next == first)
+ break;
+
+ } while (vdev_is_dead(next->l2ad_vdev));
+
+ /* if we were unable to find any usable vdevs, return NULL */
+ if (vdev_is_dead(next->l2ad_vdev))
+ next = NULL;
+
+ l2arc_dev_last = next;
+
+out:
+ mutex_exit(&l2arc_dev_mtx);
+
+ /*
+ * Grab the config lock to prevent the 'next' device from being
+ * removed while we are writing to it.
+ */
+ if (next != NULL)
+ spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
+ mutex_exit(&spa_namespace_lock);
+
+ return (next);
+}
+
+/*
+ * Free buffers that were tagged for destruction.
+ */
+static void
+l2arc_do_free_on_write()
+{
+ list_t *buflist;
+ l2arc_data_free_t *df, *df_prev;
+
+ mutex_enter(&l2arc_free_on_write_mtx);
+ buflist = l2arc_free_on_write;
+
+ for (df = list_tail(buflist); df; df = df_prev) {
+ df_prev = list_prev(buflist, df);
+ ASSERT(df->l2df_data != NULL);
+ ASSERT(df->l2df_func != NULL);
+ df->l2df_func(df->l2df_data, df->l2df_size);
+ list_remove(buflist, df);
+ kmem_free(df, sizeof (l2arc_data_free_t));
+ }
+
+ mutex_exit(&l2arc_free_on_write_mtx);
+}
+
+/*
+ * A write to a cache device has completed. Update all headers to allow
+ * reads from these buffers to begin.
+ */
+static void
+l2arc_write_done(zio_t *zio)
+{
+ l2arc_write_callback_t *cb;
+ l2arc_dev_t *dev;
+ list_t *buflist;
+ arc_buf_hdr_t *head, *ab, *ab_prev;
+ l2arc_buf_hdr_t *abl2;
+ kmutex_t *hash_lock;
+
+ cb = zio->io_private;
+ ASSERT(cb != NULL);
+ dev = cb->l2wcb_dev;
+ ASSERT(dev != NULL);
+ head = cb->l2wcb_head;
+ ASSERT(head != NULL);
+ buflist = dev->l2ad_buflist;
+ ASSERT(buflist != NULL);
+ DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
+ l2arc_write_callback_t *, cb);
+
+ if (zio->io_error != 0)
+ ARCSTAT_BUMP(arcstat_l2_writes_error);
+
+ mutex_enter(&l2arc_buflist_mtx);
+
+ /*
+ * All writes completed, or an error was hit.
+ */
+ for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
+ ab_prev = list_prev(buflist, ab);
+
+ hash_lock = HDR_LOCK(ab);
+ if (!mutex_tryenter(hash_lock)) {
+ /*
+ * This buffer misses out. It may be in a stage
+ * of eviction. Its ARC_L2_WRITING flag will be
+ * left set, denying reads to this buffer.
+ */
+ ARCSTAT_BUMP(arcstat_l2_writes_hdr_miss);
+ continue;
+ }
+
+ if (zio->io_error != 0) {
+ /*
+ * Error - drop L2ARC entry.
+ */
+ list_remove(buflist, ab);
+ abl2 = ab->b_l2hdr;
+ ab->b_l2hdr = NULL;
+ kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
+ ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
+ }
+
+ /*
+ * Allow ARC to begin reads to this L2ARC entry.
+ */
+ ab->b_flags &= ~ARC_L2_WRITING;
+
+ mutex_exit(hash_lock);
+ }
+
+ atomic_inc_64(&l2arc_writes_done);
+ list_remove(buflist, head);
+ kmem_cache_free(hdr_cache, head);
+ mutex_exit(&l2arc_buflist_mtx);
+
+ l2arc_do_free_on_write();
+
+ kmem_free(cb, sizeof (l2arc_write_callback_t));
+}
+
+/*
+ * A read to a cache device completed. Validate buffer contents before
+ * handing over to the regular ARC routines.
+ */
+static void
+l2arc_read_done(zio_t *zio)
+{
+ l2arc_read_callback_t *cb;
+ arc_buf_hdr_t *hdr;
+ arc_buf_t *buf;
+ kmutex_t *hash_lock;
+ int equal;
+
+ ASSERT(zio->io_vd != NULL);
+ ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
+
+ spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
+
+ cb = zio->io_private;
+ ASSERT(cb != NULL);
+ buf = cb->l2rcb_buf;
+ ASSERT(buf != NULL);
+
+ hash_lock = HDR_LOCK(buf->b_hdr);
+ mutex_enter(hash_lock);
+ hdr = buf->b_hdr;
+ ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
+
+ /*
+ * Check this survived the L2ARC journey.
+ */
+ equal = arc_cksum_equal(buf);
+ if (equal && zio->io_error == 0 && !HDR_L2_EVICTED(hdr)) {
+ mutex_exit(hash_lock);
+ zio->io_private = buf;
+ zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
+ zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
+ arc_read_done(zio);
+ } else {
+ mutex_exit(hash_lock);
+ /*
+ * Buffer didn't survive caching. Increment stats and
+ * reissue to the original storage device.
+ */
+ if (zio->io_error != 0) {
+ ARCSTAT_BUMP(arcstat_l2_io_error);
+ } else {
+ zio->io_error = EIO;
+ }
+ if (!equal)
+ ARCSTAT_BUMP(arcstat_l2_cksum_bad);
+
+ /*
+ * If there's no waiter, issue an async i/o to the primary
+ * storage now. If there *is* a waiter, the caller must
+ * issue the i/o in a context where it's OK to block.
+ */
+ if (zio->io_waiter == NULL) {
+ zio_t *pio = zio_unique_parent(zio);
+
+ ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
+
+ zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
+ buf->b_data, zio->io_size, arc_read_done, buf,
+ zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
+ }
+ }
+
+ kmem_free(cb, sizeof (l2arc_read_callback_t));
+}
+
+/*
+ * This is the list priority from which the L2ARC will search for pages to
+ * cache. This is used within loops (0..3) to cycle through lists in the
+ * desired order. This order can have a significant effect on cache
+ * performance.
+ *
+ * Currently the metadata lists are hit first, MFU then MRU, followed by
+ * the data lists. This function returns a locked list, and also returns
+ * the lock pointer.
+ */
+static list_t *
+l2arc_list_locked(int list_num, kmutex_t **lock)
+{
+ list_t *list;
+
+ ASSERT(list_num >= 0 && list_num <= 3);
+
+ switch (list_num) {
+ case 0:
+ list = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
+ *lock = &arc_mfu->arcs_mtx;
+ break;
+ case 1:
+ list = &arc_mru->arcs_list[ARC_BUFC_METADATA];
+ *lock = &arc_mru->arcs_mtx;
+ break;
+ case 2:
+ list = &arc_mfu->arcs_list[ARC_BUFC_DATA];
+ *lock = &arc_mfu->arcs_mtx;
+ break;
+ case 3:
+ list = &arc_mru->arcs_list[ARC_BUFC_DATA];
+ *lock = &arc_mru->arcs_mtx;
+ break;
+ }
+
+ ASSERT(!(MUTEX_HELD(*lock)));
+ mutex_enter(*lock);
+ return (list);
+}
+
+/*
+ * Evict buffers from the device write hand to the distance specified in
+ * bytes. This distance may span populated buffers, it may span nothing.
+ * This is clearing a region on the L2ARC device ready for writing.
+ * If the 'all' boolean is set, every buffer is evicted.
+ */
+static void
+l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
+{
+ list_t *buflist;
+ l2arc_buf_hdr_t *abl2;
+ arc_buf_hdr_t *ab, *ab_prev;
+ kmutex_t *hash_lock;
+ uint64_t taddr;
+
+ buflist = dev->l2ad_buflist;
+
+ if (buflist == NULL)
+ return;
+
+ if (!all && dev->l2ad_first) {
+ /*
+ * This is the first sweep through the device. There is
+ * nothing to evict.
+ */
+ return;
+ }
+
+ if (dev->l2ad_hand >= (dev->l2ad_end - (2 * distance))) {
+ /*
+ * When nearing the end of the device, evict to the end
+ * before the device write hand jumps to the start.
+ */
+ taddr = dev->l2ad_end;
+ } else {
+ taddr = dev->l2ad_hand + distance;
+ }
+ DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
+ uint64_t, taddr, boolean_t, all);
+
+top:
+ mutex_enter(&l2arc_buflist_mtx);
+ for (ab = list_tail(buflist); ab; ab = ab_prev) {
+ ab_prev = list_prev(buflist, ab);
+
+ hash_lock = HDR_LOCK(ab);
+ if (!mutex_tryenter(hash_lock)) {
+ /*
+ * Missed the hash lock. Retry.
+ */
+ ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
+ mutex_exit(&l2arc_buflist_mtx);
+ mutex_enter(hash_lock);
+ mutex_exit(hash_lock);
+ goto top;
+ }
+
+ if (HDR_L2_WRITE_HEAD(ab)) {
+ /*
+ * We hit a write head node. Leave it for
+ * l2arc_write_done().
+ */
+ list_remove(buflist, ab);
+ mutex_exit(hash_lock);
+ continue;
+ }
+
+ if (!all && ab->b_l2hdr != NULL &&
+ (ab->b_l2hdr->b_daddr > taddr ||
+ ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
+ /*
+ * We've evicted to the target address,
+ * or the end of the device.
+ */
+ mutex_exit(hash_lock);
+ break;
+ }
+
+ if (HDR_FREE_IN_PROGRESS(ab)) {
+ /*
+ * Already on the path to destruction.
+ */
+ mutex_exit(hash_lock);
+ continue;
+ }
+
+ if (ab->b_state == arc_l2c_only) {
+ ASSERT(!HDR_L2_READING(ab));
+ /*
+ * This doesn't exist in the ARC. Destroy.
+ * arc_hdr_destroy() will call list_remove()
+ * and decrement arcstat_l2_size.
+ */
+ arc_change_state(arc_anon, ab, hash_lock);
+ arc_hdr_destroy(ab);
+ } else {
+ /*
+ * Invalidate issued or about to be issued
+ * reads, since we may be about to write
+ * over this location.
+ */
+ if (HDR_L2_READING(ab)) {
+ ARCSTAT_BUMP(arcstat_l2_evict_reading);
+ ab->b_flags |= ARC_L2_EVICTED;
+ }
+
+ /*
+ * Tell ARC this no longer exists in L2ARC.
+ */
+ if (ab->b_l2hdr != NULL) {
+ abl2 = ab->b_l2hdr;
+ ab->b_l2hdr = NULL;
+ kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
+ ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
+ }
+ list_remove(buflist, ab);
+
+ /*
+ * This may have been leftover after a
+ * failed write.
+ */
+ ab->b_flags &= ~ARC_L2_WRITING;
+ }
+ mutex_exit(hash_lock);
+ }
+ mutex_exit(&l2arc_buflist_mtx);
+
+ vdev_space_update(dev->l2ad_vdev, -(taddr - dev->l2ad_evict), 0, 0);
+ dev->l2ad_evict = taddr;
+}
+
+/*
+ * Find and write ARC buffers to the L2ARC device.
+ *
+ * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
+ * for reading until they have completed writing.
+ */
+static uint64_t
+l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
+{
+ arc_buf_hdr_t *ab, *ab_prev, *head;
+ l2arc_buf_hdr_t *hdrl2;
+ list_t *list;
+ uint64_t passed_sz, write_sz, buf_sz, headroom;
+ void *buf_data;
+ kmutex_t *hash_lock, *list_lock;
+ boolean_t have_lock, full;
+ l2arc_write_callback_t *cb;
+ zio_t *pio, *wzio;
+ uint64_t guid = spa_guid(spa);
+
+ ASSERT(dev->l2ad_vdev != NULL);
+
+ pio = NULL;
+ write_sz = 0;
+ full = B_FALSE;
+ head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
+ head->b_flags |= ARC_L2_WRITE_HEAD;
+
+ /*
+ * Copy buffers for L2ARC writing.
+ */
+ mutex_enter(&l2arc_buflist_mtx);
+ for (int try = 0; try <= 3; try++) {
+ list = l2arc_list_locked(try, &list_lock);
+ passed_sz = 0;
+
+ /*
+ * L2ARC fast warmup.
+ *
+ * Until the ARC is warm and starts to evict, read from the
+ * head of the ARC lists rather than the tail.
+ */
+ headroom = target_sz * l2arc_headroom;
+ if (arc_warm == B_FALSE)
+ ab = list_head(list);
+ else
+ ab = list_tail(list);
+
+ for (; ab; ab = ab_prev) {
+ if (arc_warm == B_FALSE)
+ ab_prev = list_next(list, ab);
+ else
+ ab_prev = list_prev(list, ab);
+
+ hash_lock = HDR_LOCK(ab);
+ have_lock = MUTEX_HELD(hash_lock);
+ if (!have_lock && !mutex_tryenter(hash_lock)) {
+ /*
+ * Skip this buffer rather than waiting.
+ */
+ continue;
+ }
+
+ passed_sz += ab->b_size;
+ if (passed_sz > headroom) {
+ /*
+ * Searched too far.
+ */
+ mutex_exit(hash_lock);
+ break;
+ }
+
+ if (!l2arc_write_eligible(guid, ab)) {
+ mutex_exit(hash_lock);
+ continue;
+ }
+
+ if ((write_sz + ab->b_size) > target_sz) {
+ full = B_TRUE;
+ mutex_exit(hash_lock);
+ break;
+ }
+
+ if (pio == NULL) {
+ /*
+ * Insert a dummy header on the buflist so
+ * l2arc_write_done() can find where the
+ * write buffers begin without searching.
+ */
+ list_insert_head(dev->l2ad_buflist, head);
+
+ cb = kmem_alloc(
+ sizeof (l2arc_write_callback_t), KM_SLEEP);
+ cb->l2wcb_dev = dev;
+ cb->l2wcb_head = head;
+ pio = zio_root(spa, l2arc_write_done, cb,
+ ZIO_FLAG_CANFAIL);
+ }
+
+ /*
+ * Create and add a new L2ARC header.
+ */
+ hdrl2 = kmem_zalloc(sizeof (l2arc_buf_hdr_t), KM_SLEEP);
+ hdrl2->b_dev = dev;
+ hdrl2->b_daddr = dev->l2ad_hand;
+
+ ab->b_flags |= ARC_L2_WRITING;
+ ab->b_l2hdr = hdrl2;
+ list_insert_head(dev->l2ad_buflist, ab);
+ buf_data = ab->b_buf->b_data;
+ buf_sz = ab->b_size;
+
+ /*
+ * Compute and store the buffer cksum before
+ * writing. On debug the cksum is verified first.
+ */
+ arc_cksum_verify(ab->b_buf);
+ arc_cksum_compute(ab->b_buf, B_TRUE);
+
+ mutex_exit(hash_lock);
+
+ wzio = zio_write_phys(pio, dev->l2ad_vdev,
+ dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
+ NULL, NULL, ZIO_PRIORITY_ASYNC_WRITE,
+ ZIO_FLAG_CANFAIL, B_FALSE);
+
+ DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
+ zio_t *, wzio);
+ (void) zio_nowait(wzio);
+
+ /*
+ * Keep the clock hand suitably device-aligned.
+ */
+ buf_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
+
+ write_sz += buf_sz;
+ dev->l2ad_hand += buf_sz;
+ }
+
+ mutex_exit(list_lock);
+
+ if (full == B_TRUE)
+ break;
+ }
+ mutex_exit(&l2arc_buflist_mtx);
+
+ if (pio == NULL) {
+ ASSERT3U(write_sz, ==, 0);
+ kmem_cache_free(hdr_cache, head);
+ return (0);
+ }
+
+ ASSERT3U(write_sz, <=, target_sz);
+ ARCSTAT_BUMP(arcstat_l2_writes_sent);
+ ARCSTAT_INCR(arcstat_l2_write_bytes, write_sz);
+ ARCSTAT_INCR(arcstat_l2_size, write_sz);
+ vdev_space_update(dev->l2ad_vdev, write_sz, 0, 0);
+
+ /*
+ * Bump device hand to the device start if it is approaching the end.
+ * l2arc_evict() will already have evicted ahead for this case.
+ */
+ if (dev->l2ad_hand >= (dev->l2ad_end - target_sz)) {
+ vdev_space_update(dev->l2ad_vdev,
+ dev->l2ad_end - dev->l2ad_hand, 0, 0);
+ dev->l2ad_hand = dev->l2ad_start;
+ dev->l2ad_evict = dev->l2ad_start;
+ dev->l2ad_first = B_FALSE;
+ }
+
+ dev->l2ad_writing = B_TRUE;
+ (void) zio_wait(pio);
+ dev->l2ad_writing = B_FALSE;
+
+ return (write_sz);
+}
+
+/*
+ * This thread feeds the L2ARC at regular intervals. This is the beating
+ * heart of the L2ARC.
+ */
+static void
+l2arc_feed_thread(void)
+{
+ callb_cpr_t cpr;
+ l2arc_dev_t *dev;
+ spa_t *spa;
+ uint64_t size, wrote;
+ clock_t begin, next = ddi_get_lbolt();
+
+ CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
+
+ mutex_enter(&l2arc_feed_thr_lock);
+
+ while (l2arc_thread_exit == 0) {
+ CALLB_CPR_SAFE_BEGIN(&cpr);
+ (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
+ next);
+ CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
+ next = ddi_get_lbolt() + hz;
+
+ /*
+ * Quick check for L2ARC devices.
+ */
+ mutex_enter(&l2arc_dev_mtx);
+ if (l2arc_ndev == 0) {
+ mutex_exit(&l2arc_dev_mtx);
+ continue;
+ }
+ mutex_exit(&l2arc_dev_mtx);
+ begin = ddi_get_lbolt();
+
+ /*
+ * This selects the next l2arc device to write to, and in
+ * doing so the next spa to feed from: dev->l2ad_spa. This
+ * will return NULL if there are now no l2arc devices or if
+ * they are all faulted.
+ *
+ * If a device is returned, its spa's config lock is also
+ * held to prevent device removal. l2arc_dev_get_next()
+ * will grab and release l2arc_dev_mtx.
+ */
+ if ((dev = l2arc_dev_get_next()) == NULL)
+ continue;
+
+ spa = dev->l2ad_spa;
+ ASSERT(spa != NULL);
+
+ /*
+ * If the pool is read-only then force the feed thread to
+ * sleep a little longer.
+ */
+ if (!spa_writeable(spa)) {
+ next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
+ spa_config_exit(spa, SCL_L2ARC, dev);
+ continue;
+ }
+
+ /*
+ * Avoid contributing to memory pressure.
+ */
+ if (arc_reclaim_needed()) {
+ ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
+ spa_config_exit(spa, SCL_L2ARC, dev);
+ continue;
+ }
+
+ ARCSTAT_BUMP(arcstat_l2_feeds);
+
+ size = l2arc_write_size(dev);
+
+ /*
+ * Evict L2ARC buffers that will be overwritten.
+ */
+ l2arc_evict(dev, size, B_FALSE);
+
+ /*
+ * Write ARC buffers.
+ */
+ wrote = l2arc_write_buffers(spa, dev, size);
+
+ /*
+ * Calculate interval between writes.
+ */
+ next = l2arc_write_interval(begin, size, wrote);
+ spa_config_exit(spa, SCL_L2ARC, dev);
+ }
+
+ l2arc_thread_exit = 0;
+ cv_broadcast(&l2arc_feed_thr_cv);
+ CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
+ thread_exit();
+}
+
+boolean_t
+l2arc_vdev_present(vdev_t *vd)
+{
+ l2arc_dev_t *dev;
+
+ mutex_enter(&l2arc_dev_mtx);
+ for (dev = list_head(l2arc_dev_list); dev != NULL;
+ dev = list_next(l2arc_dev_list, dev)) {
+ if (dev->l2ad_vdev == vd)
+ break;
+ }
+ mutex_exit(&l2arc_dev_mtx);
+
+ return (dev != NULL);
+}
+
+/*
+ * Add a vdev for use by the L2ARC. By this point the spa has already
+ * validated the vdev and opened it.
+ */
+void
+l2arc_add_vdev(spa_t *spa, vdev_t *vd)
+{
+ l2arc_dev_t *adddev;
+
+ ASSERT(!l2arc_vdev_present(vd));
+
+ /*
+ * Create a new l2arc device entry.
+ */
+ adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
+ adddev->l2ad_spa = spa;
+ adddev->l2ad_vdev = vd;
+ adddev->l2ad_write = l2arc_write_max;
+ adddev->l2ad_boost = l2arc_write_boost;
+ adddev->l2ad_start = VDEV_LABEL_START_SIZE;
+ adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
+ adddev->l2ad_hand = adddev->l2ad_start;
+ adddev->l2ad_evict = adddev->l2ad_start;
+ adddev->l2ad_first = B_TRUE;
+ adddev->l2ad_writing = B_FALSE;
+ ASSERT3U(adddev->l2ad_write, >, 0);
+
+ /*
+ * This is a list of all ARC buffers that are still valid on the
+ * device.
+ */
+ adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
+ list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
+ offsetof(arc_buf_hdr_t, b_l2node));
+
+ vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
+
+ /*
+ * Add device to global list
+ */
+ mutex_enter(&l2arc_dev_mtx);
+ list_insert_head(l2arc_dev_list, adddev);
+ atomic_inc_64(&l2arc_ndev);
+ mutex_exit(&l2arc_dev_mtx);
+}
+
+/*
+ * Remove a vdev from the L2ARC.
+ */
+void
+l2arc_remove_vdev(vdev_t *vd)
+{
+ l2arc_dev_t *dev, *nextdev, *remdev = NULL;
+
+ /*
+ * Find the device by vdev
+ */
+ mutex_enter(&l2arc_dev_mtx);
+ for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
+ nextdev = list_next(l2arc_dev_list, dev);
+ if (vd == dev->l2ad_vdev) {
+ remdev = dev;
+ break;
+ }
+ }
+ ASSERT(remdev != NULL);
+
+ /*
+ * Remove device from global list
+ */
+ list_remove(l2arc_dev_list, remdev);
+ l2arc_dev_last = NULL; /* may have been invalidated */
+ atomic_dec_64(&l2arc_ndev);
+ mutex_exit(&l2arc_dev_mtx);
+
+ /*
+ * Clear all buflists and ARC references. L2ARC device flush.
+ */
+ l2arc_evict(remdev, 0, B_TRUE);
+ list_destroy(remdev->l2ad_buflist);
+ kmem_free(remdev->l2ad_buflist, sizeof (list_t));
+ kmem_free(remdev, sizeof (l2arc_dev_t));
+}
+
+void
+l2arc_init(void)
+{
+ l2arc_thread_exit = 0;
+ l2arc_ndev = 0;
+ l2arc_writes_sent = 0;
+ l2arc_writes_done = 0;
+
+ mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
+ cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
+ mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
+ mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
+ mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
+
+ l2arc_dev_list = &L2ARC_dev_list;
+ l2arc_free_on_write = &L2ARC_free_on_write;
+ list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
+ offsetof(l2arc_dev_t, l2ad_node));
+ list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
+ offsetof(l2arc_data_free_t, l2df_list_node));
+}
+
+void
+l2arc_fini(void)
+{
+ /*
+ * This is called from dmu_fini(), which is called from spa_fini();
+ * Because of this, we can assume that all l2arc devices have
+ * already been removed when the pools themselves were removed.
+ */
+
+ l2arc_do_free_on_write();
+
+ mutex_destroy(&l2arc_feed_thr_lock);
+ cv_destroy(&l2arc_feed_thr_cv);
+ mutex_destroy(&l2arc_dev_mtx);
+ mutex_destroy(&l2arc_buflist_mtx);
+ mutex_destroy(&l2arc_free_on_write_mtx);
+
+ list_destroy(l2arc_dev_list);
+ list_destroy(l2arc_free_on_write);
+}
+
+void
+l2arc_start(void)
+{
+ if (!(spa_mode_global & FWRITE))
+ return;
+
+ (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
+ TS_RUN, minclsyspri);
+}
+
+void
+l2arc_stop(void)
+{
+ if (!(spa_mode_global & FWRITE))
+ return;
+
+ mutex_enter(&l2arc_feed_thr_lock);
+ cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
+ l2arc_thread_exit = 1;
+ while (l2arc_thread_exit != 0)
+ cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
+ mutex_exit(&l2arc_feed_thr_lock);
+}