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mirror_zfs/module/zfs/arc.c
Tim Chase 40d06e3c78 Mark all ZPL and ioctl functions as PF_FSTRANS 
Prevent deadlocks by disabling direct reclaim during all ZPL and ioctl
calls as well as the l2arc and adapt ARC threads.

This obviates the need for MUTEX_FSTRANS so its previous uses and
definition have been eliminated.

Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3225
2015-04-03 11:38:59 -07:00

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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2011, 2014 by Delphix. All rights reserved.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
* Copyright 2014 Nexenta Systems, Inc. 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 therefore 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 therefore 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 therefore provide two
* types of locks: 1) the hash table lock array, and 2) the
* arc list locks.
*
* Buffers do not have their own mutexes, rather they rely on the
* hash table mutexes for the bulk of their protection (i.e. most
* fields in the arc_buf_hdr_t are protected by these mutexes).
*
* 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_clear_callback()
* and arc_do_user_evicts().
*
* It as also possible to register a callback which is run when the
* arc_meta_limit is reached and no buffers can be safely evicted. In
* this case the arc user should drop a reference on some arc buffers so
* they can be reclaimed and the arc_meta_limit honored. For example,
* when using the ZPL each dentry holds a references on a znode. These
* dentries must be pruned before the arc buffer holding the znode can
* be safely evicted.
*
* Note that the majority of the performance stats are manipulated
* with atomic operations.
*
* The L2ARC uses the l2arc_buflist_mtx global mutex for the following:
*
* - L2ARC buflist creation
* - L2ARC buflist eviction
* - L2ARC write completion, which walks L2ARC buflists
* - ARC header destruction, as it removes from L2ARC buflists
* - ARC header release, as it removes from L2ARC buflists
*/
#include <sys/spa.h>
#include <sys/zio.h>
#include <sys/zio_compress.h>
#include <sys/zfs_context.h>
#include <sys/arc.h>
#include <sys/vdev.h>
#include <sys/vdev_impl.h>
#include <sys/dsl_pool.h>
#ifdef _KERNEL
#include <sys/vmsystm.h>
#include <vm/anon.h>
#include <sys/fs/swapnode.h>
#include <sys/zpl.h>
#include <linux/mm_compat.h>
#endif
#include <sys/callb.h>
#include <sys/kstat.h>
#include <sys/dmu_tx.h>
#include <zfs_fletcher.h>
#include <sys/arc_impl.h>
#include <sys/trace_arc.h>
#ifndef _KERNEL
/* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
boolean_t arc_watch = B_FALSE;
#endif
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;
/* number of objects to prune from caches when arc_meta_limit is reached */
int zfs_arc_meta_prune = 10000;
typedef enum arc_reclaim_strategy {
ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
ARC_RECLAIM_CONS /* Conservative reclaim strategy */
} arc_reclaim_strategy_t;
/*
* The number of iterations through arc_evict_*() before we
* drop & reacquire the lock.
*/
int arc_evict_iterations = 100;
/* number of seconds before growing cache again */
int zfs_arc_grow_retry = 5;
/* disable anon data aggressively growing arc_p */
int zfs_arc_p_aggressive_disable = 1;
/* disable arc_p adapt dampener in arc_adapt */
int zfs_arc_p_dampener_disable = 1;
/* log2(fraction of arc to reclaim) */
int zfs_arc_shrink_shift = 5;
/*
* minimum lifespan of a prefetch block in clock ticks
* (initialized in arc_init())
*/
int zfs_arc_min_prefetch_lifespan = HZ;
/* disable arc proactive arc throttle due to low memory */
int zfs_arc_memory_throttle_disable = 1;
/* disable duplicate buffer eviction */
int zfs_disable_dup_eviction = 0;
/* average block used to size buf_hash_table */
int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
/*
* If this percent of memory is free, don't throttle.
*/
int arc_lotsfree_percent = 10;
static int arc_dead;
/* expiration time for arc_no_grow */
static clock_t arc_grow_time = 0;
/*
* The arc has filled available memory and has now warmed up.
*/
static boolean_t arc_warm;
/*
* These tunables are for performance analysis.
*/
unsigned long zfs_arc_max = 0;
unsigned long zfs_arc_min = 0;
unsigned long zfs_arc_meta_limit = 0;
/*
* Limit the number of restarts in arc_adjust_meta()
*/
unsigned long zfs_arc_meta_adjust_restarts = 4096;
/* 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;
/*
* Number of buffers that could not be evicted because the hash lock
* was held by another thread. The lock may not necessarily be held
* by something using the same buffer, since hash locks are shared
* by multiple buffers.
*/
kstat_named_t arcstat_mutex_miss;
/*
* Number of buffers skipped because they have I/O in progress, are
* indrect prefetch buffers that have not lived long enough, or are
* not from the spa we're trying to evict from.
*/
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_meta_size;
kstat_named_t arcstat_other_size;
kstat_named_t arcstat_anon_size;
kstat_named_t arcstat_anon_evict_data;
kstat_named_t arcstat_anon_evict_metadata;
kstat_named_t arcstat_mru_size;
kstat_named_t arcstat_mru_evict_data;
kstat_named_t arcstat_mru_evict_metadata;
kstat_named_t arcstat_mru_ghost_size;
kstat_named_t arcstat_mru_ghost_evict_data;
kstat_named_t arcstat_mru_ghost_evict_metadata;
kstat_named_t arcstat_mfu_size;
kstat_named_t arcstat_mfu_evict_data;
kstat_named_t arcstat_mfu_evict_metadata;
kstat_named_t arcstat_mfu_ghost_size;
kstat_named_t arcstat_mfu_ghost_evict_data;
kstat_named_t arcstat_mfu_ghost_evict_metadata;
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_cdata_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_asize;
kstat_named_t arcstat_l2_hdr_size;
kstat_named_t arcstat_l2_compress_successes;
kstat_named_t arcstat_l2_compress_zeros;
kstat_named_t arcstat_l2_compress_failures;
kstat_named_t arcstat_memory_throttle_count;
kstat_named_t arcstat_duplicate_buffers;
kstat_named_t arcstat_duplicate_buffers_size;
kstat_named_t arcstat_duplicate_reads;
kstat_named_t arcstat_memory_direct_count;
kstat_named_t arcstat_memory_indirect_count;
kstat_named_t arcstat_no_grow;
kstat_named_t arcstat_tempreserve;
kstat_named_t arcstat_loaned_bytes;
kstat_named_t arcstat_prune;
kstat_named_t arcstat_meta_used;
kstat_named_t arcstat_meta_limit;
kstat_named_t arcstat_meta_max;
} arc_stats_t;
static arc_stats_t arc_stats = {
{ "hits", KSTAT_DATA_UINT64 },
{ "misses", KSTAT_DATA_UINT64 },
{ "demand_data_hits", KSTAT_DATA_UINT64 },
{ "demand_data_misses", KSTAT_DATA_UINT64 },
{ "demand_metadata_hits", KSTAT_DATA_UINT64 },
{ "demand_metadata_misses", KSTAT_DATA_UINT64 },
{ "prefetch_data_hits", KSTAT_DATA_UINT64 },
{ "prefetch_data_misses", KSTAT_DATA_UINT64 },
{ "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
{ "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
{ "mru_hits", KSTAT_DATA_UINT64 },
{ "mru_ghost_hits", KSTAT_DATA_UINT64 },
{ "mfu_hits", KSTAT_DATA_UINT64 },
{ "mfu_ghost_hits", KSTAT_DATA_UINT64 },
{ "deleted", KSTAT_DATA_UINT64 },
{ "recycle_miss", KSTAT_DATA_UINT64 },
{ "mutex_miss", KSTAT_DATA_UINT64 },
{ "evict_skip", KSTAT_DATA_UINT64 },
{ "evict_l2_cached", KSTAT_DATA_UINT64 },
{ "evict_l2_eligible", KSTAT_DATA_UINT64 },
{ "evict_l2_ineligible", KSTAT_DATA_UINT64 },
{ "hash_elements", KSTAT_DATA_UINT64 },
{ "hash_elements_max", KSTAT_DATA_UINT64 },
{ "hash_collisions", KSTAT_DATA_UINT64 },
{ "hash_chains", KSTAT_DATA_UINT64 },
{ "hash_chain_max", KSTAT_DATA_UINT64 },
{ "p", KSTAT_DATA_UINT64 },
{ "c", KSTAT_DATA_UINT64 },
{ "c_min", KSTAT_DATA_UINT64 },
{ "c_max", KSTAT_DATA_UINT64 },
{ "size", KSTAT_DATA_UINT64 },
{ "hdr_size", KSTAT_DATA_UINT64 },
{ "data_size", KSTAT_DATA_UINT64 },
{ "meta_size", KSTAT_DATA_UINT64 },
{ "other_size", KSTAT_DATA_UINT64 },
{ "anon_size", KSTAT_DATA_UINT64 },
{ "anon_evict_data", KSTAT_DATA_UINT64 },
{ "anon_evict_metadata", KSTAT_DATA_UINT64 },
{ "mru_size", KSTAT_DATA_UINT64 },
{ "mru_evict_data", KSTAT_DATA_UINT64 },
{ "mru_evict_metadata", KSTAT_DATA_UINT64 },
{ "mru_ghost_size", KSTAT_DATA_UINT64 },
{ "mru_ghost_evict_data", KSTAT_DATA_UINT64 },
{ "mru_ghost_evict_metadata", KSTAT_DATA_UINT64 },
{ "mfu_size", KSTAT_DATA_UINT64 },
{ "mfu_evict_data", KSTAT_DATA_UINT64 },
{ "mfu_evict_metadata", KSTAT_DATA_UINT64 },
{ "mfu_ghost_size", KSTAT_DATA_UINT64 },
{ "mfu_ghost_evict_data", KSTAT_DATA_UINT64 },
{ "mfu_ghost_evict_metadata", 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_cdata_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_asize", KSTAT_DATA_UINT64 },
{ "l2_hdr_size", KSTAT_DATA_UINT64 },
{ "l2_compress_successes", KSTAT_DATA_UINT64 },
{ "l2_compress_zeros", KSTAT_DATA_UINT64 },
{ "l2_compress_failures", KSTAT_DATA_UINT64 },
{ "memory_throttle_count", KSTAT_DATA_UINT64 },
{ "duplicate_buffers", KSTAT_DATA_UINT64 },
{ "duplicate_buffers_size", KSTAT_DATA_UINT64 },
{ "duplicate_reads", KSTAT_DATA_UINT64 },
{ "memory_direct_count", KSTAT_DATA_UINT64 },
{ "memory_indirect_count", KSTAT_DATA_UINT64 },
{ "arc_no_grow", KSTAT_DATA_UINT64 },
{ "arc_tempreserve", KSTAT_DATA_UINT64 },
{ "arc_loaned_bytes", KSTAT_DATA_UINT64 },
{ "arc_prune", KSTAT_DATA_UINT64 },
{ "arc_meta_used", KSTAT_DATA_UINT64 },
{ "arc_meta_limit", KSTAT_DATA_UINT64 },
{ "arc_meta_max", KSTAT_DATA_UINT64 },
};
#define ARCSTAT(stat) (arc_stats.stat.value.ui64)
#define ARCSTAT_INCR(stat, val) \
atomic_add_64(&arc_stats.stat.value.ui64, (val))
#define ARCSTAT_BUMP(stat) ARCSTAT_INCR(stat, 1)
#define ARCSTAT_BUMPDOWN(stat) ARCSTAT_INCR(stat, -1)
#define ARCSTAT_MAX(stat, val) { \
uint64_t m; \
while ((val) > (m = arc_stats.stat.value.ui64) && \
(m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
continue; \
}
#define ARCSTAT_MAXSTAT(stat) \
ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
/*
* We define a macro to allow ARC hits/misses to be easily broken down by
* two separate conditions, giving a total of four different subtypes for
* each of hits and misses (so eight statistics total).
*/
#define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
if (cond1) { \
if (cond2) { \
ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
} else { \
ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
} \
} else { \
if (cond2) { \
ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
} else { \
ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
} \
}
kstat_t *arc_ksp;
static arc_state_t *arc_anon;
static arc_state_t *arc_mru;
static arc_state_t *arc_mru_ghost;
static arc_state_t *arc_mfu;
static arc_state_t *arc_mfu_ghost;
static arc_state_t *arc_l2c_only;
/*
* There are several ARC variables that are critical to export as kstats --
* but we don't want to have to grovel around in the kstat whenever we wish to
* manipulate them. For these variables, we therefore define them to be in
* terms of the statistic variable. This assures that we are not introducing
* the possibility of inconsistency by having shadow copies of the variables,
* while still allowing the code to be readable.
*/
#define arc_size ARCSTAT(arcstat_size) /* actual total arc size */
#define arc_p ARCSTAT(arcstat_p) /* target size of MRU */
#define arc_c ARCSTAT(arcstat_c) /* target size of cache */
#define arc_c_min ARCSTAT(arcstat_c_min) /* min target cache size */
#define arc_c_max ARCSTAT(arcstat_c_max) /* max target cache size */
#define arc_no_grow ARCSTAT(arcstat_no_grow)
#define arc_tempreserve ARCSTAT(arcstat_tempreserve)
#define arc_loaned_bytes ARCSTAT(arcstat_loaned_bytes)
#define arc_meta_limit ARCSTAT(arcstat_meta_limit) /* max size for metadata */
#define arc_meta_used ARCSTAT(arcstat_meta_used) /* size of metadata */
#define arc_meta_max ARCSTAT(arcstat_meta_max) /* max size of metadata */
#define L2ARC_IS_VALID_COMPRESS(_c_) \
((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY)
static list_t arc_prune_list;
static kmutex_t arc_prune_mtx;
static arc_buf_t *arc_eviction_list;
static kmutex_t arc_eviction_mtx;
static arc_buf_hdr_t arc_eviction_hdr;
static void arc_get_data_buf(arc_buf_t *buf);
static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
static int arc_evict_needed(arc_buf_contents_t type);
static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes,
arc_buf_contents_t type);
static void arc_buf_watch(arc_buf_t *buf);
static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
#define GHOST_STATE(state) \
((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
(state) == arc_l2c_only)
/*
* Private ARC flags. These flags are private ARC only flags that will show up
* in b_flags in the arc_hdr_buf_t. Some flags are publicly declared, and can
* be passed in as arc_flags in things like arc_read. However, these flags
* should never be passed and should only be set by ARC code. When adding new
* public flags, make sure not to smash the private ones.
*/
#define ARC_IN_HASH_TABLE (1 << 9) /* this buffer is hashed */
#define ARC_IO_IN_PROGRESS (1 << 10) /* I/O in progress for buf */
#define ARC_IO_ERROR (1 << 11) /* I/O failed for buf */
#define ARC_FREED_IN_READ (1 << 12) /* buf freed while in read */
#define ARC_BUF_AVAILABLE (1 << 13) /* block not in active use */
#define ARC_INDIRECT (1 << 14) /* this is an indirect block */
#define ARC_FREE_IN_PROGRESS (1 << 15) /* hdr about to be freed */
#define ARC_L2_WRITING (1 << 16) /* L2ARC write in progress */
#define ARC_L2_EVICTED (1 << 17) /* evicted during I/O */
#define ARC_L2_WRITE_HEAD (1 << 18) /* head of write list */
#define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_IN_HASH_TABLE)
#define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS)
#define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_IO_ERROR)
#define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_PREFETCH)
#define HDR_FREED_IN_READ(hdr) ((hdr)->b_flags & ARC_FREED_IN_READ)
#define HDR_BUF_AVAILABLE(hdr) ((hdr)->b_flags & ARC_BUF_AVAILABLE)
#define HDR_FREE_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
#define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_L2CACHE)
#define HDR_L2_READING(hdr) ((hdr)->b_flags & ARC_IO_IN_PROGRESS && \
(hdr)->b_l2hdr != NULL)
#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_L2_WRITING)
#define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_L2_EVICTED)
#define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_L2_WRITE_HEAD)
/*
* Other sizes
*/
#define HDR_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
#define L2HDR_SIZE ((int64_t)sizeof (l2arc_buf_hdr_t))
/*
* Hash table routines
*/
#define HT_LOCK_ALIGN 64
#define HT_LOCK_PAD (P2NPHASE(sizeof (kmutex_t), (HT_LOCK_ALIGN)))
struct ht_lock {
kmutex_t ht_lock;
#ifdef _KERNEL
unsigned char pad[HT_LOCK_PAD];
#endif
};
#define BUF_LOCKS 8192
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 */
/*
* If we discover during ARC scan any buffers to be compressed, we boost
* our headroom for the next scanning cycle by this percentage multiple.
*/
#define L2ARC_HEADROOM_BOOST 200
#define L2ARC_FEED_SECS 1 /* caching interval secs */
#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
/* L2ARC Performance Tunables */
unsigned long l2arc_write_max = L2ARC_WRITE_SIZE; /* def max write size */
unsigned long l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra warmup write */
unsigned long l2arc_headroom = L2ARC_HEADROOM; /* # of dev writes */
unsigned long l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
unsigned long l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
unsigned long l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval msecs */
int l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
int l2arc_nocompress = B_FALSE; /* don't compress bufs */
int l2arc_feed_again = B_TRUE; /* turbo warmup */
int l2arc_norw = B_FALSE; /* no reads during writes */
/*
* L2ARC Internals
*/
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_phys_t l2rcb_zb; /* original bookmark */
int l2rcb_flags; /* original flags */
enum zio_compress l2rcb_compress; /* applied compress */
} l2arc_read_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 */
/* compression applied to buffer data */
enum zio_compress b_compress;
/* real alloc'd buffer size depending on b_compress applied */
uint32_t b_hits;
uint64_t b_asize;
/* temporary buffer holder for in-flight compressed data */
void *b_tmp_cdata;
};
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 boolean_t l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr);
static void l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr,
enum zio_compress c);
static void l2arc_release_cdata_buf(arc_buf_hdr_t *ab);
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_cksum0 == 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 blkptr_t *bp, kmutex_t **lockp)
{
const dva_t *dva = BP_IDENTITY(bp);
uint64_t birth = BP_PHYSICAL_BIRTH(bp);
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(!DVA_IS_EMPTY(&buf->b_dva));
ASSERT(buf->b_birth != 0);
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 kmem_cache_t *l2arc_hdr_cache;
static void
buf_fini(void)
{
int i;
#if defined(_KERNEL) && defined(HAVE_SPL)
/*
* Large allocations which do not require contiguous pages
* should be using vmem_free() in the linux kernel\
*/
vmem_free(buf_hash_table.ht_table,
(buf_hash_table.ht_mask + 1) * sizeof (void *));
#else
kmem_free(buf_hash_table.ht_table,
(buf_hash_table.ht_mask + 1) * sizeof (void *));
#endif
for (i = 0; i < BUF_LOCKS; i++)
mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
kmem_cache_destroy(hdr_cache);
kmem_cache_destroy(buf_cache);
kmem_cache_destroy(l2arc_hdr_cache);
}
/*
* Constructor callback - called when the cache is empty
* and a new buf is requested.
*/
/* ARGSUSED */
static int
hdr_cons(void *vbuf, void *unused, int kmflag)
{
arc_buf_hdr_t *buf = vbuf;
bzero(buf, sizeof (arc_buf_hdr_t));
refcount_create(&buf->b_refcnt);
cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
list_link_init(&buf->b_arc_node);
list_link_init(&buf->b_l2node);
arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
return (0);
}
/* ARGSUSED */
static int
buf_cons(void *vbuf, void *unused, int kmflag)
{
arc_buf_t *buf = vbuf;
bzero(buf, sizeof (arc_buf_t));
mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
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);
arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
}
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 block size of zfs_arc_average_blocksize (default 8K).
* By default, the table will take up
* totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
*/
while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE)
hsize <<= 1;
retry:
buf_hash_table.ht_mask = hsize - 1;
#if defined(_KERNEL) && defined(HAVE_SPL)
/*
* Large allocations which do not require contiguous pages
* should be using vmem_alloc() in the linux kernel
*/
buf_hash_table.ht_table =
vmem_zalloc(hsize * sizeof (void*), KM_SLEEP);
#else
buf_hash_table.ht_table =
kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
#endif
if (buf_hash_table.ht_table == NULL) {
ASSERT(hsize > (1ULL << 8));
hsize >>= 1;
goto retry;
}
hdr_cache = kmem_cache_create("arc_buf_hdr_t", sizeof (arc_buf_hdr_t),
0, hdr_cons, hdr_dest, NULL, NULL, NULL, 0);
buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
l2arc_hdr_cache = kmem_cache_create("l2arc_buf_hdr_t", L2HDR_SIZE,
0, NULL, NULL, NULL, NULL, NULL, 0);
for (i = 0; i < 256; i++)
for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
*ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
for (i = 0; i < BUF_LOCKS; i++) {
mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
NULL, MUTEX_DEFAULT, NULL);
}
}
#define ARC_MINTIME (hz>>4) /* 62 ms */
static void
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);
arc_buf_watch(buf);
}
#ifndef _KERNEL
void
arc_buf_sigsegv(int sig, siginfo_t *si, void *unused)
{
panic("Got SIGSEGV at address: 0x%lx\n", (long) si->si_addr);
}
#endif
/* ARGSUSED */
static void
arc_buf_unwatch(arc_buf_t *buf)
{
#ifndef _KERNEL
if (arc_watch) {
ASSERT0(mprotect(buf->b_data, buf->b_hdr->b_size,
PROT_READ | PROT_WRITE));
}
#endif
}
/* ARGSUSED */
static void
arc_buf_watch(arc_buf_t *buf)
{
#ifndef _KERNEL
if (arc_watch)
ASSERT0(mprotect(buf->b_data, buf->b_hdr->b_size, PROT_READ));
#endif
}
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;
}
mutex_exit(&buf->b_hdr->b_freeze_lock);
arc_buf_unwatch(buf);
}
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)) {
ASSERT0(ab->b_datacnt);
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);
}
/*
* Returns detailed information about a specific arc buffer. When the
* state_index argument is set the function will calculate the arc header
* list position for its arc state. Since this requires a linear traversal
* callers are strongly encourage not to do this. However, it can be helpful
* for targeted analysis so the functionality is provided.
*/
void
arc_buf_info(arc_buf_t *ab, arc_buf_info_t *abi, int state_index)
{
arc_buf_hdr_t *hdr = ab->b_hdr;
arc_state_t *state = hdr->b_state;
memset(abi, 0, sizeof (arc_buf_info_t));
abi->abi_flags = hdr->b_flags;
abi->abi_datacnt = hdr->b_datacnt;
abi->abi_state_type = state ? state->arcs_state : ARC_STATE_ANON;
abi->abi_state_contents = hdr->b_type;
abi->abi_state_index = -1;
abi->abi_size = hdr->b_size;
abi->abi_access = hdr->b_arc_access;
abi->abi_mru_hits = hdr->b_mru_hits;
abi->abi_mru_ghost_hits = hdr->b_mru_ghost_hits;
abi->abi_mfu_hits = hdr->b_mfu_hits;
abi->abi_mfu_ghost_hits = hdr->b_mfu_ghost_hits;
abi->abi_holds = refcount_count(&hdr->b_refcnt);
if (hdr->b_l2hdr) {
abi->abi_l2arc_dattr = hdr->b_l2hdr->b_daddr;
abi->abi_l2arc_asize = hdr->b_l2hdr->b_asize;
abi->abi_l2arc_compress = hdr->b_l2hdr->b_compress;
abi->abi_l2arc_hits = hdr->b_l2hdr->b_hits;
}
if (state && state_index && list_link_active(&hdr->b_arc_node)) {
list_t *list = &state->arcs_list[hdr->b_type];
arc_buf_hdr_t *h;
mutex_enter(&state->arcs_mtx);
for (h = list_head(list); h != NULL; h = list_next(list, h)) {
abi->abi_state_index++;
if (h == hdr)
break;
}
mutex_exit(&state->arcs_mtx);
}
}
/*
* 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));
ASSERT3P(new_state, !=, old_state);
ASSERT(refcnt == 0 || ab->b_datacnt > 0);
ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
from_delta = to_delta = ab->b_datacnt * ab->b_size;
/*
* If this buffer is evictable, transfer it from the
* old state list to the new state list.
*/
if (refcnt == 0) {
if (old_state != arc_anon) {
int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx);
uint64_t *size = &old_state->arcs_lsize[ab->b_type];
if (use_mutex)
mutex_enter(&old_state->arcs_mtx);
ASSERT(list_link_active(&ab->b_arc_node));
list_remove(&old_state->arcs_list[ab->b_type], ab);
/*
* If prefetching out of the ghost cache,
* we will have a non-zero datacnt.
*/
if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
/* ghost elements have a ghost size */
ASSERT(ab->b_buf == NULL);
from_delta = ab->b_size;
}
ASSERT3U(*size, >=, from_delta);
atomic_add_64(size, -from_delta);
if (use_mutex)
mutex_exit(&old_state->arcs_mtx);
}
if (new_state != arc_anon) {
int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx);
uint64_t *size = &new_state->arcs_lsize[ab->b_type];
if (use_mutex)
mutex_enter(&new_state->arcs_mtx);
list_insert_head(&new_state->arcs_list[ab->b_type], ab);
/* ghost elements have a ghost size */
if (GHOST_STATE(new_state)) {
ASSERT(ab->b_datacnt == 0);
ASSERT(ab->b_buf == NULL);
to_delta = ab->b_size;
}
atomic_add_64(size, to_delta);
if (use_mutex)
mutex_exit(&new_state->arcs_mtx);
}
}
ASSERT(!BUF_EMPTY(ab));
if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
buf_hash_remove(ab);
/* adjust state sizes */
if (to_delta)
atomic_add_64(&new_state->arcs_size, to_delta);
if (from_delta) {
ASSERT3U(old_state->arcs_size, >=, from_delta);
atomic_add_64(&old_state->arcs_size, -from_delta);
}
ab->b_state = new_state;
/* adjust l2arc hdr stats */
if (new_state == arc_l2c_only)
l2arc_hdr_stat_add();
else if (old_state == arc_l2c_only)
l2arc_hdr_stat_remove();
}
void
arc_space_consume(uint64_t space, arc_space_type_t type)
{
ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
switch (type) {
default:
break;
case ARC_SPACE_DATA:
ARCSTAT_INCR(arcstat_data_size, space);
break;
case ARC_SPACE_META:
ARCSTAT_INCR(arcstat_meta_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;
}
if (type != ARC_SPACE_DATA) {
ARCSTAT_INCR(arcstat_meta_used, space);
if (arc_meta_max < arc_meta_used)
arc_meta_max = arc_meta_used;
}
atomic_add_64(&arc_size, space);
}
void
arc_space_return(uint64_t space, arc_space_type_t type)
{
ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
switch (type) {
default:
break;
case ARC_SPACE_DATA:
ARCSTAT_INCR(arcstat_data_size, -space);
break;
case ARC_SPACE_META:
ARCSTAT_INCR(arcstat_meta_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;
}
if (type != ARC_SPACE_DATA) {
ASSERT(arc_meta_used >= space);
ARCSTAT_INCR(arcstat_meta_used, -space);
}
ASSERT(arc_size >= space);
atomic_add_64(&arc_size, -space);
}
arc_buf_t *
arc_buf_alloc(spa_t *spa, uint64_t size, void *tag, arc_buf_contents_t type)
{
arc_buf_hdr_t *hdr;
arc_buf_t *buf;
VERIFY3U(size, <=, SPA_MAXBLOCKSIZE);
hdr = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
ASSERT(BUF_EMPTY(hdr));
hdr->b_size = size;
hdr->b_type = type;
hdr->b_spa = spa_load_guid(spa);
hdr->b_state = arc_anon;
hdr->b_arc_access = 0;
hdr->b_mru_hits = 0;
hdr->b_mru_ghost_hits = 0;
hdr->b_mfu_hits = 0;
hdr->b_mfu_ghost_hits = 0;
hdr->b_l2_hits = 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, uint64_t 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);
/*
* This buffer already exists in the arc so create a duplicate
* copy for the caller. If the buffer is associated with user data
* then track the size and number of duplicates. These stats will be
* updated as duplicate buffers are created and destroyed.
*/
if (hdr->b_type == ARC_BUFC_DATA) {
ARCSTAT_BUMP(arcstat_duplicate_buffers);
ARCSTAT_INCR(arcstat_duplicate_buffers_size, 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);
}
static void
arc_buf_free_on_write(void *data, size_t size,
void (*free_func)(void *, size_t))
{
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);
}
/*
* 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_t *buf, void (*free_func)(void *, size_t))
{
arc_buf_hdr_t *hdr = buf->b_hdr;
if (HDR_L2_WRITING(hdr)) {
arc_buf_free_on_write(buf->b_data, hdr->b_size, free_func);
ARCSTAT_BUMP(arcstat_l2_free_on_write);
} else {
free_func(buf->b_data, hdr->b_size);
}
}
/*
* Free up buf->b_data and if 'remove' is set, then pull the
* arc_buf_t off of the the arc_buf_hdr_t's list and free it.
*/
static void
arc_buf_l2_cdata_free(arc_buf_hdr_t *hdr)
{
l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
ASSERT(MUTEX_HELD(&l2arc_buflist_mtx));
if (l2hdr->b_tmp_cdata == NULL)
return;
ASSERT(HDR_L2_WRITING(hdr));
arc_buf_free_on_write(l2hdr->b_tmp_cdata, hdr->b_size,
zio_data_buf_free);
ARCSTAT_BUMP(arcstat_l2_cdata_free_on_write);
l2hdr->b_tmp_cdata = NULL;
}
static void
arc_buf_destroy(arc_buf_t *buf, boolean_t recycle, boolean_t remove)
{
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);
arc_buf_unwatch(buf);
if (!recycle) {
if (type == ARC_BUFC_METADATA) {
arc_buf_data_free(buf, zio_buf_free);
arc_space_return(size, ARC_SPACE_META);
} else {
ASSERT(type == ARC_BUFC_DATA);
arc_buf_data_free(buf, zio_data_buf_free);
arc_space_return(size, ARC_SPACE_DATA);
}
}
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;
/*
* If we're destroying a duplicate buffer make sure
* that the appropriate statistics are updated.
*/
if (buf->b_hdr->b_datacnt > 1 &&
buf->b_hdr->b_type == ARC_BUFC_DATA) {
ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
ARCSTAT_INCR(arcstat_duplicate_buffers_size, -size);
}
ASSERT(buf->b_hdr->b_datacnt > 0);
buf->b_hdr->b_datacnt -= 1;
}
/* only remove the buf if requested */
if (!remove)
return;
/* remove the buf from the hdr list */
for (bufp = &buf->b_hdr->b_buf; *bufp != buf; bufp = &(*bufp)->b_next)
continue;
*bufp = buf->b_next;
buf->b_next = NULL;
ASSERT(buf->b_efunc == NULL);
/* clean up the buf */
buf->b_hdr = NULL;
kmem_cache_free(buf_cache, buf);
}
static void
arc_hdr_destroy(arc_buf_hdr_t *hdr)
{
l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
ASSERT(refcount_is_zero(&hdr->b_refcnt));
ASSERT3P(hdr->b_state, ==, arc_anon);
ASSERT(!HDR_IO_IN_PROGRESS(hdr));
if (l2hdr != NULL) {
boolean_t buflist_held = MUTEX_HELD(&l2arc_buflist_mtx);
/*
* To prevent arc_free() and l2arc_evict() from
* attempting to free the same buffer at the same time,
* a FREE_IN_PROGRESS flag is given to arc_free() to
* give it priority. l2arc_evict() can't destroy this
* header while we are waiting on l2arc_buflist_mtx.
*
* The hdr may be removed from l2ad_buflist before we
* grab l2arc_buflist_mtx, so b_l2hdr is rechecked.
*/
if (!buflist_held) {
mutex_enter(&l2arc_buflist_mtx);
l2hdr = hdr->b_l2hdr;
}
if (l2hdr != NULL) {
list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
arc_buf_l2_cdata_free(hdr);
ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
vdev_space_update(l2hdr->b_dev->l2ad_vdev,
-l2hdr->b_asize, 0, 0);
kmem_cache_free(l2arc_hdr_cache, l2hdr);
arc_space_return(L2HDR_SIZE, ARC_SPACE_L2HDRS);
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;
}
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);
}
}
boolean_t
arc_buf_remove_ref(arc_buf_t *buf, void* tag)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
kmutex_t *hash_lock = NULL;
boolean_t 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);
}
hash_lock = HDR_LOCK(hdr);
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);
}
uint64_t
arc_buf_size(arc_buf_t *buf)
{
return (buf->b_hdr->b_size);
}
/*
* Called from the DMU to determine if the current buffer should be
* evicted. In order to ensure proper locking, the eviction must be initiated
* from the DMU. Return true if the buffer is associated with user data and
* duplicate buffers still exist.
*/
boolean_t
arc_buf_eviction_needed(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr;
boolean_t evict_needed = B_FALSE;
if (zfs_disable_dup_eviction)
return (B_FALSE);
mutex_enter(&buf->b_evict_lock);
hdr = buf->b_hdr;
if (hdr == NULL) {
/*
* We are in arc_do_user_evicts(); let that function
* perform the eviction.
*/
ASSERT(buf->b_data == NULL);
mutex_exit(&buf->b_evict_lock);
return (B_FALSE);
} else if (buf->b_data == NULL) {
/*
* We have already been added to the arc eviction list;
* recommend eviction.
*/
ASSERT3P(hdr, ==, &arc_eviction_hdr);
mutex_exit(&buf->b_evict_lock);
return (B_TRUE);
}
if (hdr->b_datacnt > 1 && hdr->b_type == ARC_BUFC_DATA)
evict_needed = B_TRUE;
mutex_exit(&buf->b_evict_lock);
return (evict_needed);
}
/*
* 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;
arc_buf_hdr_t marker = {{{ 0 }}};
int count = 0;
ASSERT(state == arc_mru || state == arc_mfu);
evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
top:
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 <
zfs_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;
/* ignore markers */
if (ab->b_spa == 0)
continue;
/*
* It may take a long time to evict all the bufs requested.
* To avoid blocking all arc activity, periodically drop
* the arcs_mtx and give other threads a chance to run
* before reacquiring the lock.
*
* If we are looking for a buffer to recycle, we are in
* the hot code path, so don't sleep.
*/
if (!recycle && count++ > arc_evict_iterations) {
list_insert_after(list, ab, &marker);
mutex_exit(&evicted_state->arcs_mtx);
mutex_exit(&state->arcs_mtx);
kpreempt(KPREEMPT_SYNC);
mutex_enter(&state->arcs_mtx);
mutex_enter(&evicted_state->arcs_mtx);
ab_prev = list_prev(list, &marker);
list_remove(list, &marker);
count = 0;
continue;
}
hash_lock = HDR_LOCK(ab);
have_lock = MUTEX_HELD(hash_lock);
if (have_lock || mutex_tryenter(hash_lock)) {
ASSERT0(refcount_count(&ab->b_refcnt));
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 (list == &state->arcs_list[ARC_BUFC_DATA] &&
(bytes < 0 || bytes_evicted < bytes)) {
/* Prevent second pass from recycling metadata into data */
recycle = FALSE;
type = ARC_BUFC_METADATA;
list = &state->arcs_list[type];
goto top;
}
if (bytes_evicted < bytes)
dprintf("only evicted %lld bytes from %x\n",
(longlong_t)bytes_evicted, state->arcs_state);
if (skipped)
ARCSTAT_INCR(arcstat_evict_skip, skipped);
if (missed)
ARCSTAT_INCR(arcstat_mutex_miss, missed);
/*
* Note: we have just evicted some data into the ghost state,
* potentially putting the ghost size over the desired size. Rather
* that evicting from the ghost list in this hot code path, leave
* this chore to the arc_reclaim_thread().
*/
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_contents_t type)
{
arc_buf_hdr_t *ab, *ab_prev;
arc_buf_hdr_t marker;
list_t *list = &state->arcs_list[type];
kmutex_t *hash_lock;
uint64_t bytes_deleted = 0;
uint64_t bufs_skipped = 0;
int count = 0;
ASSERT(GHOST_STATE(state));
bzero(&marker, sizeof (marker));
top:
mutex_enter(&state->arcs_mtx);
for (ab = list_tail(list); ab; ab = ab_prev) {
ab_prev = list_prev(list, ab);
if (ab->b_type > ARC_BUFC_NUMTYPES)
panic("invalid ab=%p", (void *)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;
/*
* It may take a long time to evict all the bufs requested.
* To avoid blocking all arc activity, periodically drop
* the arcs_mtx and give other threads a chance to run
* before reacquiring the lock.
*/
if (count++ > arc_evict_iterations) {
list_insert_after(list, ab, &marker);
mutex_exit(&state->arcs_mtx);
kpreempt(KPREEMPT_SYNC);
mutex_enter(&state->arcs_mtx);
ab_prev = list_prev(list, &marker);
list_remove(list, &marker);
count = 0;
continue;
}
if (mutex_tryenter(hash_lock)) {
ASSERT(!HDR_IO_IN_PROGRESS(ab));
ASSERT(ab->b_buf == NULL);
ARCSTAT_BUMP(arcstat_deleted);
bytes_deleted += ab->b_size;
if (ab->b_l2hdr != NULL) {
/*
* This buffer is cached on the 2nd Level ARC;
* don't destroy the header.
*/
arc_change_state(arc_l2c_only, ab, hash_lock);
mutex_exit(hash_lock);
} else {
arc_change_state(arc_anon, ab, hash_lock);
mutex_exit(hash_lock);
arc_hdr_destroy(ab);
}
DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
if (bytes >= 0 && bytes_deleted >= bytes)
break;
} else if (bytes < 0) {
/*
* Insert a list marker and then wait for the
* hash lock to become available. Once its
* available, restart from where we left off.
*/
list_insert_after(list, ab, &marker);
mutex_exit(&state->arcs_mtx);
mutex_enter(hash_lock);
mutex_exit(hash_lock);
mutex_enter(&state->arcs_mtx);
ab_prev = list_prev(list, &marker);
list_remove(list, &marker);
} else {
bufs_skipped += 1;
}
}
mutex_exit(&state->arcs_mtx);
if (list == &state->arcs_list[ARC_BUFC_DATA] &&
(bytes < 0 || bytes_deleted < bytes)) {
list = &state->arcs_list[ARC_BUFC_METADATA];
goto top;
}
if (bufs_skipped) {
ARCSTAT_INCR(arcstat_mutex_miss, bufs_skipped);
ASSERT(bytes >= 0);
}
if (bytes_deleted < bytes)
dprintf("only deleted %lld bytes from %p\n",
(longlong_t)bytes_deleted, state);
}
static void
arc_adjust(void)
{
int64_t adjustment, delta;
/*
* Adjust MRU size
*/
adjustment = MIN((int64_t)(arc_size - arc_c),
(int64_t)(arc_anon->arcs_size + arc_mru->arcs_size - arc_p));
if (adjustment > 0 && arc_mru->arcs_size > 0) {
delta = MIN(arc_mru->arcs_size, adjustment);
(void) arc_evict(arc_mru, 0, delta, FALSE, ARC_BUFC_DATA);
}
/*
* Adjust MFU size
*/
adjustment = arc_size - arc_c;
if (adjustment > 0 && arc_mfu->arcs_size > 0) {
delta = MIN(arc_mfu->arcs_size, adjustment);
(void) arc_evict(arc_mfu, 0, delta, FALSE, ARC_BUFC_DATA);
}
/*
* Adjust ghost lists
*/
adjustment = arc_mru->arcs_size + arc_mru_ghost->arcs_size - arc_c;
if (adjustment > 0 && arc_mru_ghost->arcs_size > 0) {
delta = MIN(arc_mru_ghost->arcs_size, adjustment);
arc_evict_ghost(arc_mru_ghost, 0, delta, ARC_BUFC_DATA);
}
adjustment =
arc_mru_ghost->arcs_size + arc_mfu_ghost->arcs_size - arc_c;
if (adjustment > 0 && arc_mfu_ghost->arcs_size > 0) {
delta = MIN(arc_mfu_ghost->arcs_size, adjustment);
arc_evict_ghost(arc_mfu_ghost, 0, delta, ARC_BUFC_DATA);
}
}
/*
* Request that arc user drop references so that N bytes can be released
* from the cache. This provides a mechanism to ensure the arc can honor
* the arc_meta_limit and reclaim buffers which are pinned in the cache
* by higher layers. (i.e. the zpl)
*/
static void
arc_do_user_prune(int64_t adjustment)
{
arc_prune_func_t *func;
void *private;
arc_prune_t *cp, *np;
mutex_enter(&arc_prune_mtx);
cp = list_head(&arc_prune_list);
while (cp != NULL) {
func = cp->p_pfunc;
private = cp->p_private;
np = list_next(&arc_prune_list, cp);
refcount_add(&cp->p_refcnt, func);
mutex_exit(&arc_prune_mtx);
if (func != NULL)
func(adjustment, private);
mutex_enter(&arc_prune_mtx);
/* User removed prune callback concurrently with execution */
if (refcount_remove(&cp->p_refcnt, func) == 0) {
ASSERT(!list_link_active(&cp->p_node));
refcount_destroy(&cp->p_refcnt);
kmem_free(cp, sizeof (*cp));
}
cp = np;
}
ARCSTAT_BUMP(arcstat_prune);
mutex_exit(&arc_prune_mtx);
}
static void
arc_do_user_evicts(void)
{
mutex_enter(&arc_eviction_mtx);
while (arc_eviction_list != NULL) {
arc_buf_t *buf = arc_eviction_list;
arc_eviction_list = buf->b_next;
mutex_enter(&buf->b_evict_lock);
buf->b_hdr = NULL;
mutex_exit(&buf->b_evict_lock);
mutex_exit(&arc_eviction_mtx);
if (buf->b_efunc != NULL)
VERIFY0(buf->b_efunc(buf->b_private));
buf->b_efunc = NULL;
buf->b_private = NULL;
kmem_cache_free(buf_cache, buf);
mutex_enter(&arc_eviction_mtx);
}
mutex_exit(&arc_eviction_mtx);
}
/*
* The goal of this function is to evict enough meta data buffers from the
* ARC in order to enforce the arc_meta_limit. Achieving this is slightly
* more complicated than it appears because it is common for data buffers
* to have holds on meta data buffers. In addition, dnode meta data buffers
* will be held by the dnodes in the block preventing them from being freed.
* This means we can't simply traverse the ARC and expect to always find
* enough unheld meta data buffer to release.
*
* Therefore, this function has been updated to make alternating passes
* over the ARC releasing data buffers and then newly unheld meta data
* buffers. This ensures forward progress is maintained and arc_meta_used
* will decrease. Normally this is sufficient, but if required the ARC
* will call the registered prune callbacks causing dentry and inodes to
* be dropped from the VFS cache. This will make dnode meta data buffers
* available for reclaim.
*/
static void
arc_adjust_meta(void)
{
int64_t adjustmnt, delta, prune = 0;
arc_buf_contents_t type = ARC_BUFC_DATA;
unsigned long restarts = zfs_arc_meta_adjust_restarts;
restart:
/*
* This slightly differs than the way we evict from the mru in
* arc_adjust because we don't have a "target" value (i.e. no
* "meta" arc_p). As a result, I think we can completely
* cannibalize the metadata in the MRU before we evict the
* metadata from the MFU. I think we probably need to implement a
* "metadata arc_p" value to do this properly.
*/
adjustmnt = arc_meta_used - arc_meta_limit;
if (adjustmnt > 0 && arc_mru->arcs_lsize[type] > 0) {
delta = MIN(arc_mru->arcs_lsize[type], adjustmnt);
arc_evict(arc_mru, 0, delta, FALSE, type);
adjustmnt -= delta;
}
/*
* We can't afford to recalculate adjustmnt here. If we do,
* new metadata buffers can sneak into the MRU or ANON lists,
* thus penalize the MFU metadata. Although the fudge factor is
* small, it has been empirically shown to be significant for
* certain workloads (e.g. creating many empty directories). As
* such, we use the original calculation for adjustmnt, and
* simply decrement the amount of data evicted from the MRU.
*/
if (adjustmnt > 0 && arc_mfu->arcs_lsize[type] > 0) {
delta = MIN(arc_mfu->arcs_lsize[type], adjustmnt);
arc_evict(arc_mfu, 0, delta, FALSE, type);
}
adjustmnt = arc_meta_used - arc_meta_limit;
if (adjustmnt > 0 && arc_mru_ghost->arcs_lsize[type] > 0) {
delta = MIN(adjustmnt,
arc_mru_ghost->arcs_lsize[type]);
arc_evict_ghost(arc_mru_ghost, 0, delta, type);
adjustmnt -= delta;
}
if (adjustmnt > 0 && arc_mfu_ghost->arcs_lsize[type] > 0) {
delta = MIN(adjustmnt,
arc_mfu_ghost->arcs_lsize[type]);
arc_evict_ghost(arc_mfu_ghost, 0, delta, type);
}
/*
* If after attempting to make the requested adjustment to the ARC
* the meta limit is still being exceeded then request that the
* higher layers drop some cached objects which have holds on ARC
* meta buffers. Requests to the upper layers will be made with
* increasingly large scan sizes until the ARC is below the limit.
*/
if (arc_meta_used > arc_meta_limit) {
if (type == ARC_BUFC_DATA) {
type = ARC_BUFC_METADATA;
} else {
type = ARC_BUFC_DATA;
if (zfs_arc_meta_prune) {
prune += zfs_arc_meta_prune;
arc_do_user_prune(prune);
}
}
if (restarts > 0) {
restarts--;
goto restart;
}
}
}
/*
* 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_load_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_BUFC_DATA);
arc_evict_ghost(arc_mfu_ghost, guid, -1, ARC_BUFC_DATA);
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(uint64_t bytes)
{
if (arc_c > arc_c_min) {
uint64_t to_free;
to_free = bytes ? bytes : arc_c >> zfs_arc_shrink_shift;
if (arc_c > arc_c_min + to_free)
atomic_add_64(&arc_c, -to_free);
else
arc_c = arc_c_min;
to_free = bytes ? bytes : arc_p >> zfs_arc_shrink_shift;
if (arc_p > to_free)
atomic_add_64(&arc_p, -to_free);
else
arc_p = 0;
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 void
arc_kmem_reap_now(arc_reclaim_strategy_t strat, uint64_t bytes)
{
size_t i;
kmem_cache_t *prev_cache = NULL;
kmem_cache_t *prev_data_cache = NULL;
extern kmem_cache_t *zio_buf_cache[];
extern kmem_cache_t *zio_data_buf_cache[];
/*
* An aggressive reclamation will shrink the cache size as well as
* reap free buffers from the arc kmem caches.
*/
if (strat == ARC_RECLAIM_AGGR)
arc_shrink(bytes);
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);
}
/*
* Unlike other ZFS implementations this thread is only responsible for
* adapting the target ARC size on Linux. The responsibility for memory
* reclamation has been entirely delegated to the arc_shrinker_func()
* which is registered with the VM. To reflect this change in behavior
* the arc_reclaim thread has been renamed to arc_adapt.
*/
static void
arc_adapt_thread(void)
{
callb_cpr_t cpr;
fstrans_cookie_t cookie;
CALLB_CPR_INIT(&cpr, &arc_reclaim_thr_lock, callb_generic_cpr, FTAG);
cookie = spl_fstrans_mark();
mutex_enter(&arc_reclaim_thr_lock);
while (arc_thread_exit == 0) {
#ifndef _KERNEL
arc_reclaim_strategy_t last_reclaim = ARC_RECLAIM_CONS;
if (spa_get_random(100) == 0) {
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 */
arc_grow_time = ddi_get_lbolt() +
(zfs_arc_grow_retry * hz);
arc_kmem_reap_now(last_reclaim, 0);
arc_warm = B_TRUE;
}
#endif /* !_KERNEL */
/* No recent memory pressure allow the ARC to grow. */
if (arc_no_grow &&
ddi_time_after_eq(ddi_get_lbolt(), arc_grow_time))
arc_no_grow = FALSE;
arc_adjust_meta();
arc_adjust();
if (arc_eviction_list != NULL)
arc_do_user_evicts();
/* block until needed, or one second, whichever is shorter */
CALLB_CPR_SAFE_BEGIN(&cpr);
(void) cv_timedwait_interruptible(&arc_reclaim_thr_cv,
&arc_reclaim_thr_lock, (ddi_get_lbolt() + hz));
CALLB_CPR_SAFE_END(&cpr, &arc_reclaim_thr_lock);
/* Allow the module options to be changed */
if (zfs_arc_max > 64 << 20 &&
zfs_arc_max < physmem * PAGESIZE &&
zfs_arc_max != arc_c_max)
arc_c_max = zfs_arc_max;
if (zfs_arc_min > 0 &&
zfs_arc_min < arc_c_max &&
zfs_arc_min != arc_c_min)
arc_c_min = zfs_arc_min;
if (zfs_arc_meta_limit > 0 &&
zfs_arc_meta_limit <= arc_c_max &&
zfs_arc_meta_limit != arc_meta_limit)
arc_meta_limit = zfs_arc_meta_limit;
}
arc_thread_exit = 0;
cv_broadcast(&arc_reclaim_thr_cv);
CALLB_CPR_EXIT(&cpr); /* drops arc_reclaim_thr_lock */
spl_fstrans_unmark(cookie);
thread_exit();
}
#ifdef _KERNEL
/*
* Determine the amount of memory eligible for eviction contained in the
* ARC. All clean data reported by the ghost lists can always be safely
* evicted. Due to arc_c_min, the same does not hold for all clean data
* contained by the regular mru and mfu lists.
*
* In the case of the regular mru and mfu lists, we need to report as
* much clean data as possible, such that evicting that same reported
* data will not bring arc_size below arc_c_min. Thus, in certain
* circumstances, the total amount of clean data in the mru and mfu
* lists might not actually be evictable.
*
* The following two distinct cases are accounted for:
*
* 1. The sum of the amount of dirty data contained by both the mru and
* mfu lists, plus the ARC's other accounting (e.g. the anon list),
* is greater than or equal to arc_c_min.
* (i.e. amount of dirty data >= arc_c_min)
*
* This is the easy case; all clean data contained by the mru and mfu
* lists is evictable. Evicting all clean data can only drop arc_size
* to the amount of dirty data, which is greater than arc_c_min.
*
* 2. The sum of the amount of dirty data contained by both the mru and
* mfu lists, plus the ARC's other accounting (e.g. the anon list),
* is less than arc_c_min.
* (i.e. arc_c_min > amount of dirty data)
*
* 2.1. arc_size is greater than or equal arc_c_min.
* (i.e. arc_size >= arc_c_min > amount of dirty data)
*
* In this case, not all clean data from the regular mru and mfu
* lists is actually evictable; we must leave enough clean data
* to keep arc_size above arc_c_min. Thus, the maximum amount of
* evictable data from the two lists combined, is exactly the
* difference between arc_size and arc_c_min.
*
* 2.2. arc_size is less than arc_c_min
* (i.e. arc_c_min > arc_size > amount of dirty data)
*
* In this case, none of the data contained in the mru and mfu
* lists is evictable, even if it's clean. Since arc_size is
* already below arc_c_min, evicting any more would only
* increase this negative difference.
*/
static uint64_t
arc_evictable_memory(void) {
uint64_t arc_clean =
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];
uint64_t ghost_clean =
arc_mru_ghost->arcs_lsize[ARC_BUFC_DATA] +
arc_mru_ghost->arcs_lsize[ARC_BUFC_METADATA] +
arc_mfu_ghost->arcs_lsize[ARC_BUFC_DATA] +
arc_mfu_ghost->arcs_lsize[ARC_BUFC_METADATA];
uint64_t arc_dirty = MAX((int64_t)arc_size - (int64_t)arc_clean, 0);
if (arc_dirty >= arc_c_min)
return (ghost_clean + arc_clean);
return (ghost_clean + MAX((int64_t)arc_size - (int64_t)arc_c_min, 0));
}
/*
* If sc->nr_to_scan is zero, the caller is requesting a query of the
* number of objects which can potentially be freed. If it is nonzero,
* the request is to free that many objects.
*
* Linux kernels >= 3.12 have the count_objects and scan_objects callbacks
* in struct shrinker and also require the shrinker to return the number
* of objects freed.
*
* Older kernels require the shrinker to return the number of freeable
* objects following the freeing of nr_to_free.
*/
static spl_shrinker_t
__arc_shrinker_func(struct shrinker *shrink, struct shrink_control *sc)
{
int64_t pages;
/* The arc is considered warm once reclaim has occurred */
if (unlikely(arc_warm == B_FALSE))
arc_warm = B_TRUE;
/* Return the potential number of reclaimable pages */
pages = btop((int64_t)arc_evictable_memory());
if (sc->nr_to_scan == 0)
return (pages);
/* Not allowed to perform filesystem reclaim */
if (!(sc->gfp_mask & __GFP_FS))
return (SHRINK_STOP);
/* Reclaim in progress */
if (mutex_tryenter(&arc_reclaim_thr_lock) == 0)
return (SHRINK_STOP);
/*
* Evict the requested number of pages by shrinking arc_c the
* requested amount. If there is nothing left to evict just
* reap whatever we can from the various arc slabs.
*/
if (pages > 0) {
arc_kmem_reap_now(ARC_RECLAIM_AGGR, ptob(sc->nr_to_scan));
#ifdef HAVE_SPLIT_SHRINKER_CALLBACK
pages = MAX(pages - btop(arc_evictable_memory()), 0);
#else
pages = btop(arc_evictable_memory());
#endif
} else {
arc_kmem_reap_now(ARC_RECLAIM_CONS, ptob(sc->nr_to_scan));
pages = SHRINK_STOP;
}
/*
* When direct reclaim is observed it usually indicates a rapid
* increase in memory pressure. This occurs because the kswapd
* threads were unable to asynchronously keep enough free memory
* available. In this case set arc_no_grow to briefly pause arc
* growth to avoid compounding the memory pressure.
*/
if (current_is_kswapd()) {
ARCSTAT_BUMP(arcstat_memory_indirect_count);
} else {
arc_no_grow = B_TRUE;
arc_grow_time = ddi_get_lbolt() + (zfs_arc_grow_retry * hz);
ARCSTAT_BUMP(arcstat_memory_direct_count);
}
mutex_exit(&arc_reclaim_thr_lock);
return (pages);
}
SPL_SHRINKER_CALLBACK_WRAPPER(arc_shrinker_func);
SPL_SHRINKER_DECLARE(arc_shrinker, arc_shrinker_func, DEFAULT_SEEKS);
#endif /* _KERNEL */
/*
* Adapt arc info given the number of bytes we are trying to add and
* the state that we are comming from. This function is only called
* when we are adding new content to the cache.
*/
static void
arc_adapt(int bytes, arc_state_t *state)
{
int mult;
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));
if (!zfs_arc_p_dampener_disable)
mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
arc_p = MIN(arc_c, 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));
if (!zfs_arc_p_dampener_disable)
mult = MIN(mult, 10);
delta = MIN(bytes * mult, arc_p);
arc_p = MAX(0, arc_p - delta);
}
ASSERT((int64_t)arc_p >= 0);
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);
if (arc_no_grow)
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_buf_contents_t evict = ARC_BUFC_DATA;
boolean_t recycle = TRUE;
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_META);
} else {
ASSERT(type == ARC_BUFC_DATA);
buf->b_data = zio_data_buf_alloc(size);
arc_space_consume(size, ARC_SPACE_DATA);
}
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;
}
/*
* Evict data buffers prior to metadata buffers, unless we're
* over the metadata limit and adding a metadata buffer.
*/
if (type == ARC_BUFC_METADATA) {
if (arc_meta_used >= arc_meta_limit)
evict = ARC_BUFC_METADATA;
else
/*
* In this case, we're evicting data while
* adding metadata. Thus, to prevent recycling a
* data buffer into a metadata buffer, recycling
* is disabled in the following arc_evict call.
*/
recycle = FALSE;
}
if ((buf->b_data = arc_evict(state, 0, size, recycle, evict)) == NULL) {
if (type == ARC_BUFC_METADATA) {
buf->b_data = zio_buf_alloc(size);
arc_space_consume(size, ARC_SPACE_META);
/*
* If we are unable to recycle an existing meta buffer
* signal the reclaim thread. It will notify users
* via the prune callback to drop references. The
* prune callback in run in the context of the reclaim
* thread to avoid deadlocking on the hash_lock.
* Of course, only do this when recycle is true.
*/
if (recycle)
cv_signal(&arc_reclaim_thr_cv);
} else {
ASSERT(type == ARC_BUFC_DATA);
buf->b_data = zio_data_buf_alloc(size);
arc_space_consume(size, ARC_SPACE_DATA);
}
/* Only bump this if we tried to recycle and failed */
if (recycle)
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 (!zfs_arc_p_aggressive_disable &&
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;
atomic_inc_32(&buf->b_mru_hits);
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 (ddi_time_after(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);
}
atomic_inc_32(&buf->b_mru_hits);
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);
atomic_inc_32(&buf->b_mru_ghost_hits);
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));
}
atomic_inc_32(&buf->b_mfu_hits);
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.
*/
ASSERT0(refcount_count(&buf->b_refcnt));
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);
atomic_inc_32(&buf->b_mfu_ghost_hits);
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 {
cmn_err(CE_PANIC, "invalid arc state 0x%p", buf->b_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));
}
/* 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));
*bufp = NULL;
} else {
*bufp = buf;
ASSERT(buf->b_data);
}
}
static void
arc_read_done(zio_t *zio)
{
arc_buf_hdr_t *hdr;
arc_buf_t *buf;
arc_buf_t *abuf; /* buffer we're assigning to callback */
kmutex_t *hash_lock = NULL;
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.
*/
if (HDR_IN_HASH_TABLE(hdr)) {
arc_buf_hdr_t *found;
ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
ASSERT3U(hdr->b_dva.dva_word[0], ==,
BP_IDENTITY(zio->io_bp)->dva_word[0]);
ASSERT3U(hdr->b_dva.dva_word[1], ==,
BP_IDENTITY(zio->io_bp)->dva_word[1]);
found = buf_hash_find(hdr->b_spa, zio->io_bp,
&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) {
dmu_object_byteswap_t bswap =
DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
if (BP_GET_LEVEL(zio->io_bp) > 0)
byteswap_uint64_array(buf->b_data, hdr->b_size);
else
dmu_ot_byteswap[bswap].ob_func(buf->b_data, hdr->b_size);
}
arc_cksum_compute(buf, B_FALSE);
arc_buf_watch(buf);
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) {
ARCSTAT_BUMP(arcstat_duplicate_reads);
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 at the specified DVA (in bp) via the
* cache. If the block is found in the cache, invoke the provided
* callback immediately and return. Note that the `zio' parameter
* in the callback will be NULL in this case, since no IO was
* required. If the block is not in the cache pass the read request
* on to the spa with a substitute callback function, so that the
* requested block will be added to the cache.
*
* If a read request arrives for a block that has a read in-progress,
* either wait for the in-progress read to complete (and return the
* results); or, if this is a read with a "done" func, add a record
* to the read to invoke the "done" func when the read completes,
* and return; or just return.
*
* arc_read_done() will invoke all the requested "done" functions
* for readers of this block.
*/
int
arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
void *private, zio_priority_t priority, int zio_flags, uint32_t *arc_flags,
const zbookmark_phys_t *zb)
{
arc_buf_hdr_t *hdr = NULL;
arc_buf_t *buf = NULL;
kmutex_t *hash_lock = NULL;
zio_t *rzio;
uint64_t guid = spa_load_guid(spa);
int rc = 0;
ASSERT(!BP_IS_EMBEDDED(bp) ||
BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
top:
if (!BP_IS_EMBEDDED(bp)) {
/*
* Embedded BP's have no DVA and require no I/O to "read".
* Create an anonymous arc buf to back it.
*/
hdr = buf_hash_find(guid, bp, &hash_lock);
}
if (hdr != NULL && 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);
goto out;
}
mutex_exit(hash_lock);
goto out;
}
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;
if (*arc_flags & ARC_L2COMPRESS)
hdr->b_flags |= ARC_L2COMPRESS;
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 = 0;
boolean_t devw = B_FALSE;
enum zio_compress b_compress = ZIO_COMPRESS_OFF;
uint64_t b_asize = 0;
/*
* Gracefully handle a damaged logical block size as a
* checksum error by passing a dummy zio to the done callback.
*/
if (size > SPA_MAXBLOCKSIZE) {
if (done) {
rzio = zio_null(pio, spa, NULL,
NULL, NULL, zio_flags);
rzio->io_error = ECKSUM;
done(rzio, buf, private);
zio_nowait(rzio);
}
rc = ECKSUM;
goto out;
}
if (hdr == NULL) {
/* this block is not in the cache */
arc_buf_hdr_t *exists = NULL;
arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
buf = arc_buf_alloc(spa, size, private, type);
hdr = buf->b_hdr;
if (!BP_IS_EMBEDDED(bp)) {
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 != NULL) {
/* 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 (*arc_flags & ARC_L2COMPRESS)
hdr->b_flags |= ARC_L2COMPRESS;
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));
ASSERT0(refcount_count(&hdr->b_refcnt));
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;
if (*arc_flags & ARC_L2COMPRESS)
hdr->b_flags |= ARC_L2COMPRESS;
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->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;
b_compress = hdr->b_l2hdr->b_compress;
b_asize = hdr->b_l2hdr->b_asize;
/*
* Lock out device removal.
*/
if (vdev_is_dead(vd) ||
!spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
vd = NULL;
}
if (hash_lock != NULL)
mutex_exit(hash_lock);
/*
* At this point, we have a level 1 cache miss. Try again in
* L2ARC if possible.
*/
ASSERT3U(hdr->b_size, ==, size);
DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
uint64_t, size, zbookmark_phys_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);
atomic_inc_32(&hdr->b_l2hdr->b_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;
cb->l2rcb_compress = b_compress;
ASSERT(addr >= VDEV_LABEL_START_SIZE &&
addr + size < vd->vdev_psize -
VDEV_LABEL_END_SIZE);
/*
* l2arc read. The SCL_L2ARC lock will be
* released by l2arc_read_done().
* Issue a null zio if the underlying buffer
* was squashed to zero size by compression.
*/
if (b_compress == ZIO_COMPRESS_EMPTY) {
rzio = zio_null(pio, spa, vd,
l2arc_read_done, cb,
zio_flags | ZIO_FLAG_DONT_CACHE |
ZIO_FLAG_CANFAIL |
ZIO_FLAG_DONT_PROPAGATE |
ZIO_FLAG_DONT_RETRY);
} else {
rzio = zio_read_phys(pio, vd, addr,
b_asize, 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, b_asize);
if (*arc_flags & ARC_NOWAIT) {
zio_nowait(rzio);
goto out;
}
ASSERT(*arc_flags & ARC_WAIT);
if (zio_wait(rzio) == 0)
goto out;
/* 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) {
rc = zio_wait(rzio);
goto out;
}
ASSERT(*arc_flags & ARC_NOWAIT);
zio_nowait(rzio);
}
out:
spa_read_history_add(spa, zb, *arc_flags);
return (rc);
}
arc_prune_t *
arc_add_prune_callback(arc_prune_func_t *func, void *private)
{
arc_prune_t *p;
p = kmem_alloc(sizeof (*p), KM_SLEEP);
p->p_pfunc = func;
p->p_private = private;
list_link_init(&p->p_node);
refcount_create(&p->p_refcnt);
mutex_enter(&arc_prune_mtx);
refcount_add(&p->p_refcnt, &arc_prune_list);
list_insert_head(&arc_prune_list, p);
mutex_exit(&arc_prune_mtx);
return (p);
}
void
arc_remove_prune_callback(arc_prune_t *p)
{
mutex_enter(&arc_prune_mtx);
list_remove(&arc_prune_list, p);
if (refcount_remove(&p->p_refcnt, &arc_prune_list) == 0) {
refcount_destroy(&p->p_refcnt);
kmem_free(p, sizeof (*p));
}
mutex_exit(&arc_prune_mtx);
}
void
arc_set_callback(arc_buf_t *buf, arc_evict_func_t *func, void *private)
{
ASSERT(buf->b_hdr != NULL);
ASSERT(buf->b_hdr->b_state != arc_anon);
ASSERT(!refcount_is_zero(&buf->b_hdr->b_refcnt) || func == NULL);
ASSERT(buf->b_efunc == NULL);
ASSERT(!HDR_BUF_AVAILABLE(buf->b_hdr));
buf->b_efunc = func;
buf->b_private = private;
}
/*
* Notify the arc that a block was freed, and thus will never be used again.
*/
void
arc_freed(spa_t *spa, const blkptr_t *bp)
{
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
uint64_t guid = spa_load_guid(spa);
ASSERT(!BP_IS_EMBEDDED(bp));
hdr = buf_hash_find(guid, bp, &hash_lock);
if (hdr == NULL)
return;
if (HDR_BUF_AVAILABLE(hdr)) {
arc_buf_t *buf = hdr->b_buf;
add_reference(hdr, hash_lock, FTAG);
hdr->b_flags &= ~ARC_BUF_AVAILABLE;
mutex_exit(hash_lock);
arc_release(buf, FTAG);
(void) arc_buf_remove_ref(buf, FTAG);
} else {
mutex_exit(hash_lock);
}
}
/*
* Clear the user eviction callback set by arc_set_callback(), first calling
* it if it exists. Because the presence of a callback keeps an arc_buf cached
* clearing the callback may result in the arc_buf being destroyed. However,
* it will not result in the *last* arc_buf being destroyed, hence the data
* will remain cached in the ARC. We make a copy of the arc buffer here so
* that we can process the callback without holding any locks.
*
* It's possible that the callback is already in the process of being cleared
* by another thread. In this case we can not clear the callback.
*
* Returns B_TRUE if the callback was successfully called and cleared.
*/
boolean_t
arc_clear_callback(arc_buf_t *buf)
{
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock;
arc_evict_func_t *efunc = buf->b_efunc;
void *private = buf->b_private;
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 (B_FALSE);
} else if (buf->b_data == NULL) {
/*
* 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);
VERIFY0(efunc(private));
return (B_TRUE);
}
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);
buf->b_efunc = NULL;
buf->b_private = NULL;
if (hdr->b_datacnt > 1) {
mutex_exit(&buf->b_evict_lock);
arc_buf_destroy(buf, FALSE, TRUE);
} else {
ASSERT(buf == hdr->b_buf);
hdr->b_flags |= ARC_BUF_AVAILABLE;
mutex_exit(&buf->b_evict_lock);
}
mutex_exit(hash_lock);
VERIFY0(efunc(private));
return (B_TRUE);
}
/*
* Release this buffer from the cache, making it an anonymous buffer. This
* must be done after a read and prior to modifying the buffer contents.
* If the buffer has more than one reference, we must make
* a new hdr for the buffer.
*/
void
arc_release(arc_buf_t *buf, void *tag)
{
arc_buf_hdr_t *hdr;
kmutex_t *hash_lock = NULL;
l2arc_buf_hdr_t *l2hdr;
uint64_t buf_size = 0;
/*
* It would be nice to assert that if it's DMU metadata (level >
* 0 || it's the dnode file), then it must be syncing context.
* But we don't know that information at this level.
*/
mutex_enter(&buf->b_evict_lock);
hdr = buf->b_hdr;
/* this buffer is not on any list */
ASSERT(refcount_count(&hdr->b_refcnt) > 0);
if (hdr->b_state == arc_anon) {
/* this buffer is already released */
ASSERT(buf->b_efunc == NULL);
} else {
hash_lock = HDR_LOCK(hdr);
mutex_enter(hash_lock);
hdr = buf->b_hdr;
ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
}
l2hdr = hdr->b_l2hdr;
if (l2hdr) {
mutex_enter(&l2arc_buflist_mtx);
arc_buf_l2_cdata_free(hdr);
hdr->b_l2hdr = NULL;
list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
}
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);
}
/*
* We're releasing a duplicate user data buffer, update
* our statistics accordingly.
*/
if (hdr->b_type == ARC_BUFC_DATA) {
ARCSTAT_BUMPDOWN(arcstat_duplicate_buffers);
ARCSTAT_INCR(arcstat_duplicate_buffers_size,
-hdr->b_size);
}
hdr->b_datacnt -= 1;
arc_cksum_verify(buf);
arc_buf_unwatch(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_mru_hits = 0;
nhdr->b_mru_ghost_hits = 0;
nhdr->b_mfu_hits = 0;
nhdr->b_mfu_ghost_hits = 0;
nhdr->b_l2_hits = 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;
hdr->b_mru_hits = 0;
hdr->b_mru_ghost_hits = 0;
hdr->b_mfu_hits = 0;
hdr->b_mfu_ghost_hits = 0;
hdr->b_l2_hits = 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) {
ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
vdev_space_update(l2hdr->b_dev->l2ad_vdev,
-l2hdr->b_asize, 0, 0);
kmem_cache_free(l2arc_hdr_cache, l2hdr);
arc_space_return(L2HDR_SIZE, ARC_SPACE_L2HDRS);
ARCSTAT_INCR(arcstat_l2_size, -buf_size);
mutex_exit(&l2arc_buflist_mtx);
}
}
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);
}
#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;
}
/*
* The SPA calls this callback for each physical write that happens on behalf
* of a logical write. See the comment in dbuf_write_physdone() for details.
*/
static void
arc_write_physdone(zio_t *zio)
{
arc_write_callback_t *cb = zio->io_private;
if (cb->awcb_physdone != NULL)
cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
}
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) {
if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
buf_discard_identity(hdr);
} else {
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 or compressed enough to be
* embedded in the BP, 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 if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
/* nopwrite */
ASSERT(zio->io_prop.zp_nopwrite);
if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
panic("bad nopwrite, hdr=%p exists=%p",
(void *)hdr, (void *)exists);
} 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, boolean_t l2arc_compress,
const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone,
arc_done_func_t *done, void *private, zio_priority_t priority,
int zio_flags, const zbookmark_phys_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;
if (l2arc_compress)
hdr->b_flags |= ARC_L2COMPRESS;
callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
callback->awcb_ready = ready;
callback->awcb_physdone = physdone;
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_physdone, arc_write_done, callback,
priority, zio_flags, zb);
return (zio);
}
static int
arc_memory_throttle(uint64_t reserve, uint64_t txg)
{
#ifdef _KERNEL
if (zfs_arc_memory_throttle_disable)
return (0);
if (freemem <= physmem * arc_lotsfree_percent / 100) {
ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
DMU_TX_STAT_BUMP(dmu_tx_memory_reclaim);
return (SET_ERROR(EAGAIN));
}
#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;
if (reserve > arc_c/4 && !arc_no_grow)
arc_c = MIN(arc_c_max, reserve * 4);
/*
* Throttle when the calculated memory footprint for the TXG
* exceeds the target ARC size.
*/
if (reserve > arc_c) {
DMU_TX_STAT_BUMP(dmu_tx_memory_reserve);
return (SET_ERROR(ERESTART));
}
/*
* 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 therefore need to
* make sure that there is sufficient available memory for this.
*/
error = arc_memory_throttle(reserve, txg);
if (error != 0)
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);
DMU_TX_STAT_BUMP(dmu_tx_dirty_throttle);
return (SET_ERROR(ERESTART));
}
atomic_add_64(&arc_tempreserve, reserve);
return (0);
}
static void
arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
kstat_named_t *evict_data, kstat_named_t *evict_metadata)
{
size->value.ui64 = state->arcs_size;
evict_data->value.ui64 = state->arcs_lsize[ARC_BUFC_DATA];
evict_metadata->value.ui64 = state->arcs_lsize[ARC_BUFC_METADATA];
}
static int
arc_kstat_update(kstat_t *ksp, int rw)
{
arc_stats_t *as = ksp->ks_data;
if (rw == KSTAT_WRITE) {
return (SET_ERROR(EACCES));
} else {
arc_kstat_update_state(arc_anon,
&as->arcstat_anon_size,
&as->arcstat_anon_evict_data,
&as->arcstat_anon_evict_metadata);
arc_kstat_update_state(arc_mru,
&as->arcstat_mru_size,
&as->arcstat_mru_evict_data,
&as->arcstat_mru_evict_metadata);
arc_kstat_update_state(arc_mru_ghost,
&as->arcstat_mru_ghost_size,
&as->arcstat_mru_ghost_evict_data,
&as->arcstat_mru_ghost_evict_metadata);
arc_kstat_update_state(arc_mfu,
&as->arcstat_mfu_size,
&as->arcstat_mfu_evict_data,
&as->arcstat_mfu_evict_metadata);
arc_kstat_update_state(arc_mfu_ghost,
&as->arcstat_mfu_ghost_size,
&as->arcstat_mfu_ghost_evict_data,
&as->arcstat_mfu_ghost_evict_metadata);
}
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 */
zfs_arc_min_prefetch_lifespan = 1 * hz;
/* Start out with 1/8 of all memory */
arc_c = physmem * PAGESIZE / 8;
#ifdef _KERNEL
/*
* On architectures where the physical memory can be larger
* than the addressable space (intel in 32-bit mode), we may
* need to limit the cache to 1/8 of VM size.
*/
arc_c = MIN(arc_c, vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 8);
/*
* Register a shrinker to support synchronous (direct) memory
* reclaim from the arc. This is done to prevent kswapd from
* swapping out pages when it is preferable to shrink the arc.
*/
spl_register_shrinker(&arc_shrinker);
#endif
/* set min cache to zero */
arc_c_min = 4<<20;
/* set max to 1/2 of all memory */
arc_c_max = arc_c * 4;
/*
* 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 > 0 && 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 3/4 of the arc capacity */
arc_meta_limit = (3 * arc_c_max) / 4;
arc_meta_max = 0;
/* Allow the tunable to override if it is reasonable */
if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
arc_meta_limit = zfs_arc_meta_limit;
/* if 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));
arc_anon->arcs_state = ARC_STATE_ANON;
arc_mru->arcs_state = ARC_STATE_MRU;
arc_mru_ghost->arcs_state = ARC_STATE_MRU_GHOST;
arc_mfu->arcs_state = ARC_STATE_MFU;
arc_mfu_ghost->arcs_state = ARC_STATE_MFU_GHOST;
arc_l2c_only->arcs_state = ARC_STATE_L2C_ONLY;
buf_init();
arc_thread_exit = 0;
list_create(&arc_prune_list, sizeof (arc_prune_t),
offsetof(arc_prune_t, p_node));
arc_eviction_list = NULL;
mutex_init(&arc_prune_mtx, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&arc_eviction_mtx, NULL, MUTEX_DEFAULT, NULL);
bzero(&arc_eviction_hdr, sizeof (arc_buf_hdr_t));
arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
if (arc_ksp != NULL) {
arc_ksp->ks_data = &arc_stats;
arc_ksp->ks_update = arc_kstat_update;
kstat_install(arc_ksp);
}
(void) thread_create(NULL, 0, arc_adapt_thread, NULL, 0, &p0,
TS_RUN, minclsyspri);
arc_dead = FALSE;
arc_warm = B_FALSE;
/*
* Calculate maximum amount of dirty data per pool.
*
* If it has been set by a module parameter, take that.
* Otherwise, use a percentage of physical memory defined by
* zfs_dirty_data_max_percent (default 10%) with a cap at
* zfs_dirty_data_max_max (default 25% of physical memory).
*/
if (zfs_dirty_data_max_max == 0)
zfs_dirty_data_max_max = physmem * PAGESIZE *
zfs_dirty_data_max_max_percent / 100;
if (zfs_dirty_data_max == 0) {
zfs_dirty_data_max = physmem * PAGESIZE *
zfs_dirty_data_max_percent / 100;
zfs_dirty_data_max = MIN(zfs_dirty_data_max,
zfs_dirty_data_max_max);
}
}
void
arc_fini(void)
{
arc_prune_t *p;
mutex_enter(&arc_reclaim_thr_lock);
#ifdef _KERNEL
spl_unregister_shrinker(&arc_shrinker);
#endif /* _KERNEL */
arc_thread_exit = 1;
while (arc_thread_exit != 0)
cv_wait(&arc_reclaim_thr_cv, &arc_reclaim_thr_lock);
mutex_exit(&arc_reclaim_thr_lock);
arc_flush(NULL);
arc_dead = TRUE;
if (arc_ksp != NULL) {
kstat_delete(arc_ksp);
arc_ksp = NULL;
}
mutex_enter(&arc_prune_mtx);
while ((p = list_head(&arc_prune_list)) != NULL) {
list_remove(&arc_prune_list, p);
refcount_remove(&p->p_refcnt, &arc_prune_list);
refcount_destroy(&p->p_refcnt);
kmem_free(p, sizeof (*p));
}
mutex_exit(&arc_prune_mtx);
list_destroy(&arc_prune_list);
mutex_destroy(&arc_prune_mtx);
mutex_destroy(&arc_eviction_mtx);
mutex_destroy(&arc_reclaim_thr_lock);
cv_destroy(&arc_reclaim_thr_cv);
list_destroy(&arc_mru->arcs_list[ARC_BUFC_METADATA]);
list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
list_destroy(&arc_mfu->arcs_list[ARC_BUFC_METADATA]);
list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
list_destroy(&arc_mru->arcs_list[ARC_BUFC_DATA]);
list_destroy(&arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
list_destroy(&arc_mfu->arcs_list[ARC_BUFC_DATA]);
list_destroy(&arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
mutex_destroy(&arc_anon->arcs_mtx);
mutex_destroy(&arc_mru->arcs_mtx);
mutex_destroy(&arc_mru_ghost->arcs_mtx);
mutex_destroy(&arc_mfu->arcs_mtx);
mutex_destroy(&arc_mfu_ghost->arcs_mtx);
mutex_destroy(&arc_l2c_only->arcs_mtx);
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. If a compressible buffer is
* found during scanning and selected for writing to an L2ARC device, we
* temporarily boost scanning headroom during the next scan cycle to make
* sure we adapt to compression effects (which might significantly reduce
* the data volume we write to L2ARC). 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_nocompress skip compressing buffers
* l2arc_headroom number of max device writes to precache
* l2arc_headroom_boost when we find compressed buffers during ARC
* scanning, we multiply headroom by this
* percentage factor for the next scan cycle,
* since more compressed buffers are likely to
* be present
* 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(void)
{
uint64_t size;
/*
* Make sure our globals have meaningful values in case the user
* altered them.
*/
size = l2arc_write_max;
if (size == 0) {
cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
"be greater than zero, resetting it to the default (%d)",
L2ARC_WRITE_SIZE);
size = l2arc_write_max = L2ARC_WRITE_SIZE;
}
if (arc_warm == B_FALSE)
size += l2arc_write_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);
ARCSTAT_INCR(arcstat_hdr_size, -HDR_SIZE);
}
static void
l2arc_hdr_stat_remove(void)
{
ARCSTAT_INCR(arcstat_l2_hdr_size, -HDR_SIZE);
ARCSTAT_INCR(arcstat_hdr_size, HDR_SIZE);
}
/*
* Cycle through L2ARC devices. This is how L2ARC load balances.
* If a device is returned, this also returns holding the spa config lock.
*/
static l2arc_dev_t *
l2arc_dev_get_next(void)
{
l2arc_dev_t *first, *next = NULL;
/*
* Lock out the removal of spas (spa_namespace_lock), then removal
* of cache devices (l2arc_dev_mtx). Once a device has been selected,
* both locks will be dropped and a spa config lock held instead.
*/
mutex_enter(&spa_namespace_lock);
mutex_enter(&l2arc_dev_mtx);
/* if there are no vdevs, there is nothing to do */
if (l2arc_ndev == 0)
goto out;
first = NULL;
next = l2arc_dev_last;
do {
/* loop around the list looking for a non-faulted vdev */
if (next == NULL) {
next = list_head(l2arc_dev_list);
} else {
next = list_next(l2arc_dev_list, next);
if (next == NULL)
next = list_head(l2arc_dev_list);
}
/* if we have come back to the start, bail out */
if (first == NULL)
first = next;
else if (next == first)
break;
} while (vdev_is_dead(next->l2ad_vdev));
/* if we were unable to find any usable vdevs, return NULL */
if (vdev_is_dead(next->l2ad_vdev))
next = NULL;
l2arc_dev_last = next;
out:
mutex_exit(&l2arc_dev_mtx);
/*
* Grab the config lock to prevent the 'next' device from being
* removed while we are writing to it.
*/
if (next != NULL)
spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
mutex_exit(&spa_namespace_lock);
return (next);
}
/*
* Free buffers that were tagged for destruction.
*/
static void
l2arc_do_free_on_write(void)
{
list_t *buflist;
l2arc_data_free_t *df, *df_prev;
mutex_enter(&l2arc_free_on_write_mtx);
buflist = l2arc_free_on_write;
for (df = list_tail(buflist); df; df = df_prev) {
df_prev = list_prev(buflist, df);
ASSERT(df->l2df_data != NULL);
ASSERT(df->l2df_func != NULL);
df->l2df_func(df->l2df_data, df->l2df_size);
list_remove(buflist, df);
kmem_free(df, sizeof (l2arc_data_free_t));
}
mutex_exit(&l2arc_free_on_write_mtx);
}
/*
* A write to a cache device has completed. Update all headers to allow
* reads from these buffers to begin.
*/
static void
l2arc_write_done(zio_t *zio)
{
l2arc_write_callback_t *cb;
l2arc_dev_t *dev;
list_t *buflist;
arc_buf_hdr_t *head, *ab, *ab_prev;
l2arc_buf_hdr_t *abl2;
kmutex_t *hash_lock;
int64_t bytes_dropped = 0;
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);
abl2 = ab->b_l2hdr;
/*
* Release the temporary compressed buffer as soon as possible.
*/
if (abl2->b_compress != ZIO_COMPRESS_OFF)
l2arc_release_cdata_buf(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);
ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
bytes_dropped += abl2->b_asize;
ab->b_l2hdr = NULL;
kmem_cache_free(l2arc_hdr_cache, abl2);
arc_space_return(L2HDR_SIZE, ARC_SPACE_L2HDRS);
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);
vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
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));
/*
* If the buffer was compressed, decompress it first.
*/
if (cb->l2rcb_compress != ZIO_COMPRESS_OFF)
l2arc_decompress_zio(zio, hdr, cb->l2rcb_compress);
ASSERT(zio->io_data != NULL);
/*
* 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 = SET_ERROR(EIO);
}
if (!equal)
ARCSTAT_BUMP(arcstat_l2_cksum_bad);
/*
* If there's no waiter, issue an async i/o to the primary
* storage now. If there *is* a waiter, the caller must
* issue the i/o in a context where it's OK to block.
*/
if (zio->io_waiter == NULL) {
zio_t *pio = zio_unique_parent(zio);
ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
zio_nowait(zio_read(pio, cb->l2rcb_spa, &cb->l2rcb_bp,
buf->b_data, zio->io_size, arc_read_done, buf,
zio->io_priority, cb->l2rcb_flags, &cb->l2rcb_zb));
}
}
kmem_free(cb, sizeof (l2arc_read_callback_t));
}
/*
* This is the list priority from which the L2ARC will search for pages to
* cache. This is used within loops (0..3) to cycle through lists in the
* desired order. This order can have a significant effect on cache
* performance.
*
* Currently the metadata lists are hit first, MFU then MRU, followed by
* the data lists. This function returns a locked list, and also returns
* the lock pointer.
*/
static list_t *
l2arc_list_locked(int list_num, kmutex_t **lock)
{
list_t *list = NULL;
ASSERT(list_num >= 0 && list_num <= 3);
switch (list_num) {
case 0:
list = &arc_mfu->arcs_list[ARC_BUFC_METADATA];
*lock = &arc_mfu->arcs_mtx;
break;
case 1:
list = &arc_mru->arcs_list[ARC_BUFC_METADATA];
*lock = &arc_mru->arcs_mtx;
break;
case 2:
list = &arc_mfu->arcs_list[ARC_BUFC_DATA];
*lock = &arc_mfu->arcs_mtx;
break;
case 3:
list = &arc_mru->arcs_list[ARC_BUFC_DATA];
*lock = &arc_mru->arcs_mtx;
break;
}
ASSERT(!(MUTEX_HELD(*lock)));
mutex_enter(*lock);
return (list);
}
/*
* Evict buffers from the device write hand to the distance specified in
* bytes. This distance may span populated buffers, it may span nothing.
* This is clearing a region on the L2ARC device ready for writing.
* If the 'all' boolean is set, every buffer is evicted.
*/
static void
l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
{
list_t *buflist;
l2arc_buf_hdr_t *abl2;
arc_buf_hdr_t *ab, *ab_prev;
kmutex_t *hash_lock;
uint64_t taddr;
int64_t bytes_evicted = 0;
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;
ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
bytes_evicted += abl2->b_asize;
ab->b_l2hdr = NULL;
/*
* We are destroying l2hdr, so ensure that
* its compressed buffer, if any, is not leaked.
*/
ASSERT(abl2->b_tmp_cdata == NULL);
kmem_cache_free(l2arc_hdr_cache, abl2);
arc_space_return(L2HDR_SIZE, ARC_SPACE_L2HDRS);
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, -bytes_evicted, 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.
* The headroom_boost is an in-out parameter used to maintain headroom boost
* state between calls to this function.
*
* Returns the number of bytes actually written (which may be smaller than
* the delta by which the device hand has changed due to alignment).
*/
static uint64_t
l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
boolean_t *headroom_boost)
{
arc_buf_hdr_t *ab, *ab_prev, *head;
list_t *list;
uint64_t write_asize, write_psize, write_sz, headroom,
buf_compress_minsz;
void *buf_data;
kmutex_t *list_lock = NULL;
boolean_t full;
l2arc_write_callback_t *cb;
zio_t *pio, *wzio;
uint64_t guid = spa_load_guid(spa);
int try;
const boolean_t do_headroom_boost = *headroom_boost;
ASSERT(dev->l2ad_vdev != NULL);
/* Lower the flag now, we might want to raise it again later. */
*headroom_boost = B_FALSE;
pio = NULL;
write_sz = write_asize = write_psize = 0;
full = B_FALSE;
head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
head->b_flags |= ARC_L2_WRITE_HEAD;
/*
* We will want to try to compress buffers that are at least 2x the
* device sector size.
*/
buf_compress_minsz = 2 << dev->l2ad_vdev->vdev_ashift;
/*
* Copy buffers for L2ARC writing.
*/
mutex_enter(&l2arc_buflist_mtx);
for (try = 0; try <= 3; try++) {
uint64_t passed_sz = 0;
list = l2arc_list_locked(try, &list_lock);
/*
* L2ARC fast warmup.
*
* Until the ARC is warm and starts to evict, read from the
* head of the ARC lists rather than the tail.
*/
if (arc_warm == B_FALSE)
ab = list_head(list);
else
ab = list_tail(list);
headroom = target_sz * l2arc_headroom;
if (do_headroom_boost)
headroom = (headroom * l2arc_headroom_boost) / 100;
for (; ab; ab = ab_prev) {
l2arc_buf_hdr_t *l2hdr;
kmutex_t *hash_lock;
uint64_t buf_sz;
if (arc_warm == B_FALSE)
ab_prev = list_next(list, ab);
else
ab_prev = list_prev(list, ab);
hash_lock = HDR_LOCK(ab);
if (!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.
*/
l2hdr = kmem_cache_alloc(l2arc_hdr_cache, KM_SLEEP);
l2hdr->b_dev = dev;
l2hdr->b_daddr = 0;
arc_space_consume(L2HDR_SIZE, ARC_SPACE_L2HDRS);
ab->b_flags |= ARC_L2_WRITING;
/*
* Temporarily stash the data buffer in b_tmp_cdata.
* The subsequent write step will pick it up from
* there. This is because can't access ab->b_buf
* without holding the hash_lock, which we in turn
* can't access without holding the ARC list locks
* (which we want to avoid during compression/writing)
*/
l2hdr->b_compress = ZIO_COMPRESS_OFF;
l2hdr->b_asize = ab->b_size;
l2hdr->b_tmp_cdata = ab->b_buf->b_data;
l2hdr->b_hits = 0;
buf_sz = ab->b_size;
ab->b_l2hdr = l2hdr;
list_insert_head(dev->l2ad_buflist, ab);
/*
* 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);
write_sz += buf_sz;
}
mutex_exit(list_lock);
if (full == B_TRUE)
break;
}
/* No buffers selected for writing? */
if (pio == NULL) {
ASSERT0(write_sz);
mutex_exit(&l2arc_buflist_mtx);
kmem_cache_free(hdr_cache, head);
return (0);
}
/*
* Now start writing the buffers. We're starting at the write head
* and work backwards, retracing the course of the buffer selector
* loop above.
*/
for (ab = list_prev(dev->l2ad_buflist, head); ab;
ab = list_prev(dev->l2ad_buflist, ab)) {
l2arc_buf_hdr_t *l2hdr;
uint64_t buf_sz;
/*
* We shouldn't need to lock the buffer here, since we flagged
* it as ARC_L2_WRITING in the previous step, but we must take
* care to only access its L2 cache parameters. In particular,
* ab->b_buf may be invalid by now due to ARC eviction.
*/
l2hdr = ab->b_l2hdr;
l2hdr->b_daddr = dev->l2ad_hand;
if (!l2arc_nocompress && (ab->b_flags & ARC_L2COMPRESS) &&
l2hdr->b_asize >= buf_compress_minsz) {
if (l2arc_compress_buf(l2hdr)) {
/*
* If compression succeeded, enable headroom
* boost on the next scan cycle.
*/
*headroom_boost = B_TRUE;
}
}
/*
* Pick up the buffer data we had previously stashed away
* (and now potentially also compressed).
*/
buf_data = l2hdr->b_tmp_cdata;
buf_sz = l2hdr->b_asize;
/*
* If the data has not been compressed, then clear b_tmp_cdata
* to make sure that it points only to a temporary compression
* buffer.
*/
if (!L2ARC_IS_VALID_COMPRESS(l2hdr->b_compress))
l2hdr->b_tmp_cdata = NULL;
/* Compression may have squashed the buffer to zero length. */
if (buf_sz != 0) {
uint64_t buf_p_sz;
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);
write_asize += buf_sz;
/*
* Keep the clock hand suitably device-aligned.
*/
buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
write_psize += buf_p_sz;
dev->l2ad_hand += buf_p_sz;
}
}
mutex_exit(&l2arc_buflist_mtx);
ASSERT3U(write_asize, <=, target_sz);
ARCSTAT_BUMP(arcstat_l2_writes_sent);
ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize);
ARCSTAT_INCR(arcstat_l2_size, write_sz);
ARCSTAT_INCR(arcstat_l2_asize, write_asize);
vdev_space_update(dev->l2ad_vdev, write_asize, 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)) {
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_asize);
}
/*
* Compresses an L2ARC buffer.
* The data to be compressed must be prefilled in l2hdr->b_tmp_cdata and its
* size in l2hdr->b_asize. This routine tries to compress the data and
* depending on the compression result there are three possible outcomes:
* *) The buffer was incompressible. The original l2hdr contents were left
* untouched and are ready for writing to an L2 device.
* *) The buffer was all-zeros, so there is no need to write it to an L2
* device. To indicate this situation b_tmp_cdata is NULL'ed, b_asize is
* set to zero and b_compress is set to ZIO_COMPRESS_EMPTY.
* *) Compression succeeded and b_tmp_cdata was replaced with a temporary
* data buffer which holds the compressed data to be written, and b_asize
* tells us how much data there is. b_compress is set to the appropriate
* compression algorithm. Once writing is done, invoke
* l2arc_release_cdata_buf on this l2hdr to free this temporary buffer.
*
* Returns B_TRUE if compression succeeded, or B_FALSE if it didn't (the
* buffer was incompressible).
*/
static boolean_t
l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr)
{
void *cdata;
size_t csize, len, rounded;
ASSERT(l2hdr->b_compress == ZIO_COMPRESS_OFF);
ASSERT(l2hdr->b_tmp_cdata != NULL);
len = l2hdr->b_asize;
cdata = zio_data_buf_alloc(len);
csize = zio_compress_data(ZIO_COMPRESS_LZ4, l2hdr->b_tmp_cdata,
cdata, l2hdr->b_asize);
rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE);
if (rounded > csize) {
bzero((char *)cdata + csize, rounded - csize);
csize = rounded;
}
if (csize == 0) {
/* zero block, indicate that there's nothing to write */
zio_data_buf_free(cdata, len);
l2hdr->b_compress = ZIO_COMPRESS_EMPTY;
l2hdr->b_asize = 0;
l2hdr->b_tmp_cdata = NULL;
ARCSTAT_BUMP(arcstat_l2_compress_zeros);
return (B_TRUE);
} else if (csize > 0 && csize < len) {
/*
* Compression succeeded, we'll keep the cdata around for
* writing and release it afterwards.
*/
l2hdr->b_compress = ZIO_COMPRESS_LZ4;
l2hdr->b_asize = csize;
l2hdr->b_tmp_cdata = cdata;
ARCSTAT_BUMP(arcstat_l2_compress_successes);
return (B_TRUE);
} else {
/*
* Compression failed, release the compressed buffer.
* l2hdr will be left unmodified.
*/
zio_data_buf_free(cdata, len);
ARCSTAT_BUMP(arcstat_l2_compress_failures);
return (B_FALSE);
}
}
/*
* Decompresses a zio read back from an l2arc device. On success, the
* underlying zio's io_data buffer is overwritten by the uncompressed
* version. On decompression error (corrupt compressed stream), the
* zio->io_error value is set to signal an I/O error.
*
* Please note that the compressed data stream is not checksummed, so
* if the underlying device is experiencing data corruption, we may feed
* corrupt data to the decompressor, so the decompressor needs to be
* able to handle this situation (LZ4 does).
*/
static void
l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c)
{
uint64_t csize;
void *cdata;
ASSERT(L2ARC_IS_VALID_COMPRESS(c));
if (zio->io_error != 0) {
/*
* An io error has occured, just restore the original io
* size in preparation for a main pool read.
*/
zio->io_orig_size = zio->io_size = hdr->b_size;
return;
}
if (c == ZIO_COMPRESS_EMPTY) {
/*
* An empty buffer results in a null zio, which means we
* need to fill its io_data after we're done restoring the
* buffer's contents.
*/
ASSERT(hdr->b_buf != NULL);
bzero(hdr->b_buf->b_data, hdr->b_size);
zio->io_data = zio->io_orig_data = hdr->b_buf->b_data;
} else {
ASSERT(zio->io_data != NULL);
/*
* We copy the compressed data from the start of the arc buffer
* (the zio_read will have pulled in only what we need, the
* rest is garbage which we will overwrite at decompression)
* and then decompress back to the ARC data buffer. This way we
* can minimize copying by simply decompressing back over the
* original compressed data (rather than decompressing to an
* aux buffer and then copying back the uncompressed buffer,
* which is likely to be much larger).
*/
csize = zio->io_size;
cdata = zio_data_buf_alloc(csize);
bcopy(zio->io_data, cdata, csize);
if (zio_decompress_data(c, cdata, zio->io_data, csize,
hdr->b_size) != 0)
zio->io_error = SET_ERROR(EIO);
zio_data_buf_free(cdata, csize);
}
/* Restore the expected uncompressed IO size. */
zio->io_orig_size = zio->io_size = hdr->b_size;
}
/*
* Releases the temporary b_tmp_cdata buffer in an l2arc header structure.
* This buffer serves as a temporary holder of compressed data while
* the buffer entry is being written to an l2arc device. Once that is
* done, we can dispose of it.
*/
static void
l2arc_release_cdata_buf(arc_buf_hdr_t *ab)
{
l2arc_buf_hdr_t *l2hdr = ab->b_l2hdr;
ASSERT(L2ARC_IS_VALID_COMPRESS(l2hdr->b_compress));
if (l2hdr->b_compress != ZIO_COMPRESS_EMPTY) {
/*
* If the data was compressed, then we've allocated a
* temporary buffer for it, so now we need to release it.
*/
ASSERT(l2hdr->b_tmp_cdata != NULL);
zio_data_buf_free(l2hdr->b_tmp_cdata, ab->b_size);
l2hdr->b_tmp_cdata = NULL;
} else {
ASSERT(l2hdr->b_tmp_cdata == NULL);
}
}
/*
* 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();
boolean_t headroom_boost = B_FALSE;
fstrans_cookie_t cookie;
CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
mutex_enter(&l2arc_feed_thr_lock);
cookie = spl_fstrans_mark();
while (l2arc_thread_exit == 0) {
CALLB_CPR_SAFE_BEGIN(&cpr);
(void) cv_timedwait_interruptible(&l2arc_feed_thr_cv,
&l2arc_feed_thr_lock, next);
CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
next = ddi_get_lbolt() + hz;
/*
* Quick check for L2ARC devices.
*/
mutex_enter(&l2arc_dev_mtx);
if (l2arc_ndev == 0) {
mutex_exit(&l2arc_dev_mtx);
continue;
}
mutex_exit(&l2arc_dev_mtx);
begin = ddi_get_lbolt();
/*
* This selects the next l2arc device to write to, and in
* doing so the next spa to feed from: dev->l2ad_spa. This
* will return NULL if there are now no l2arc devices or if
* they are all faulted.
*
* If a device is returned, its spa's config lock is also
* held to prevent device removal. l2arc_dev_get_next()
* will grab and release l2arc_dev_mtx.
*/
if ((dev = l2arc_dev_get_next()) == NULL)
continue;
spa = dev->l2ad_spa;
ASSERT(spa != NULL);
/*
* If the pool is read-only then force the feed thread to
* sleep a little longer.
*/
if (!spa_writeable(spa)) {
next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
spa_config_exit(spa, SCL_L2ARC, dev);
continue;
}
/*
* Avoid contributing to memory pressure.
*/
if (arc_no_grow) {
ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
spa_config_exit(spa, SCL_L2ARC, dev);
continue;
}
ARCSTAT_BUMP(arcstat_l2_feeds);
size = l2arc_write_size();
/*
* Evict L2ARC buffers that will be overwritten.
*/
l2arc_evict(dev, size, B_FALSE);
/*
* Write ARC buffers.
*/
wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost);
/*
* Calculate interval between writes.
*/
next = l2arc_write_interval(begin, size, wrote);
spa_config_exit(spa, SCL_L2ARC, dev);
}
spl_fstrans_unmark(cookie);
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_start = VDEV_LABEL_START_SIZE;
adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
adddev->l2ad_hand = adddev->l2ad_start;
adddev->l2ad_evict = adddev->l2ad_start;
adddev->l2ad_first = B_TRUE;
adddev->l2ad_writing = B_FALSE;
list_link_init(&adddev->l2ad_node);
/*
* This is a list of all ARC buffers that are still valid on the
* device.
*/
adddev->l2ad_buflist = kmem_zalloc(sizeof (list_t), KM_SLEEP);
list_create(adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
offsetof(arc_buf_hdr_t, b_l2node));
vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
/*
* Add device to global list
*/
mutex_enter(&l2arc_dev_mtx);
list_insert_head(l2arc_dev_list, adddev);
atomic_inc_64(&l2arc_ndev);
mutex_exit(&l2arc_dev_mtx);
}
/*
* Remove a vdev from the L2ARC.
*/
void
l2arc_remove_vdev(vdev_t *vd)
{
l2arc_dev_t *dev, *nextdev, *remdev = NULL;
/*
* Find the device by vdev
*/
mutex_enter(&l2arc_dev_mtx);
for (dev = list_head(l2arc_dev_list); dev; dev = nextdev) {
nextdev = list_next(l2arc_dev_list, dev);
if (vd == dev->l2ad_vdev) {
remdev = dev;
break;
}
}
ASSERT(remdev != NULL);
/*
* Remove device from global list
*/
list_remove(l2arc_dev_list, remdev);
l2arc_dev_last = NULL; /* may have been invalidated */
atomic_dec_64(&l2arc_ndev);
mutex_exit(&l2arc_dev_mtx);
/*
* Clear all buflists and ARC references. L2ARC device flush.
*/
l2arc_evict(remdev, 0, B_TRUE);
list_destroy(remdev->l2ad_buflist);
kmem_free(remdev->l2ad_buflist, sizeof (list_t));
kmem_free(remdev, sizeof (l2arc_dev_t));
}
void
l2arc_init(void)
{
l2arc_thread_exit = 0;
l2arc_ndev = 0;
l2arc_writes_sent = 0;
l2arc_writes_done = 0;
mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&l2arc_buflist_mtx, NULL, MUTEX_DEFAULT, NULL);
mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
l2arc_dev_list = &L2ARC_dev_list;
l2arc_free_on_write = &L2ARC_free_on_write;
list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
offsetof(l2arc_dev_t, l2ad_node));
list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
offsetof(l2arc_data_free_t, l2df_list_node));
}
void
l2arc_fini(void)
{
/*
* This is called from dmu_fini(), which is called from spa_fini();
* Because of this, we can assume that all l2arc devices have
* already been removed when the pools themselves were removed.
*/
l2arc_do_free_on_write();
mutex_destroy(&l2arc_feed_thr_lock);
cv_destroy(&l2arc_feed_thr_cv);
mutex_destroy(&l2arc_dev_mtx);
mutex_destroy(&l2arc_buflist_mtx);
mutex_destroy(&l2arc_free_on_write_mtx);
list_destroy(l2arc_dev_list);
list_destroy(l2arc_free_on_write);
}
void
l2arc_start(void)
{
if (!(spa_mode_global & FWRITE))
return;
(void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
TS_RUN, minclsyspri);
}
void
l2arc_stop(void)
{
if (!(spa_mode_global & FWRITE))
return;
mutex_enter(&l2arc_feed_thr_lock);
cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
l2arc_thread_exit = 1;
while (l2arc_thread_exit != 0)
cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
mutex_exit(&l2arc_feed_thr_lock);
}
#if defined(_KERNEL) && defined(HAVE_SPL)
EXPORT_SYMBOL(arc_buf_size);
EXPORT_SYMBOL(arc_write);
EXPORT_SYMBOL(arc_read);
EXPORT_SYMBOL(arc_buf_remove_ref);
EXPORT_SYMBOL(arc_buf_info);
EXPORT_SYMBOL(arc_getbuf_func);
EXPORT_SYMBOL(arc_add_prune_callback);
EXPORT_SYMBOL(arc_remove_prune_callback);
module_param(zfs_arc_min, ulong, 0644);
MODULE_PARM_DESC(zfs_arc_min, "Min arc size");
module_param(zfs_arc_max, ulong, 0644);
MODULE_PARM_DESC(zfs_arc_max, "Max arc size");
module_param(zfs_arc_meta_limit, ulong, 0644);
MODULE_PARM_DESC(zfs_arc_meta_limit, "Meta limit for arc size");
module_param(zfs_arc_meta_prune, int, 0644);
MODULE_PARM_DESC(zfs_arc_meta_prune, "Meta objects to scan for prune");
module_param(zfs_arc_meta_adjust_restarts, ulong, 0644);
MODULE_PARM_DESC(zfs_arc_meta_adjust_restarts,
"Limit number of restarts in arc_adjust_meta");
module_param(zfs_arc_grow_retry, int, 0644);
MODULE_PARM_DESC(zfs_arc_grow_retry, "Seconds before growing arc size");
module_param(zfs_arc_p_aggressive_disable, int, 0644);
MODULE_PARM_DESC(zfs_arc_p_aggressive_disable, "disable aggressive arc_p grow");
module_param(zfs_arc_p_dampener_disable, int, 0644);
MODULE_PARM_DESC(zfs_arc_p_dampener_disable, "disable arc_p adapt dampener");
module_param(zfs_arc_shrink_shift, int, 0644);
MODULE_PARM_DESC(zfs_arc_shrink_shift, "log2(fraction of arc to reclaim)");
module_param(zfs_disable_dup_eviction, int, 0644);
MODULE_PARM_DESC(zfs_disable_dup_eviction, "disable duplicate buffer eviction");
module_param(zfs_arc_average_blocksize, int, 0444);
MODULE_PARM_DESC(zfs_arc_average_blocksize, "Target average block size");
module_param(zfs_arc_memory_throttle_disable, int, 0644);
MODULE_PARM_DESC(zfs_arc_memory_throttle_disable, "disable memory throttle");
module_param(zfs_arc_min_prefetch_lifespan, int, 0644);
MODULE_PARM_DESC(zfs_arc_min_prefetch_lifespan, "Min life of prefetch block");
module_param(l2arc_write_max, ulong, 0644);
MODULE_PARM_DESC(l2arc_write_max, "Max write bytes per interval");
module_param(l2arc_write_boost, ulong, 0644);
MODULE_PARM_DESC(l2arc_write_boost, "Extra write bytes during device warmup");
module_param(l2arc_headroom, ulong, 0644);
MODULE_PARM_DESC(l2arc_headroom, "Number of max device writes to precache");
module_param(l2arc_headroom_boost, ulong, 0644);
MODULE_PARM_DESC(l2arc_headroom_boost, "Compressed l2arc_headroom multiplier");
module_param(l2arc_feed_secs, ulong, 0644);
MODULE_PARM_DESC(l2arc_feed_secs, "Seconds between L2ARC writing");
module_param(l2arc_feed_min_ms, ulong, 0644);
MODULE_PARM_DESC(l2arc_feed_min_ms, "Min feed interval in milliseconds");
module_param(l2arc_noprefetch, int, 0644);
MODULE_PARM_DESC(l2arc_noprefetch, "Skip caching prefetched buffers");
module_param(l2arc_nocompress, int, 0644);
MODULE_PARM_DESC(l2arc_nocompress, "Skip compressing L2ARC buffers");
module_param(l2arc_feed_again, int, 0644);
MODULE_PARM_DESC(l2arc_feed_again, "Turbo L2ARC warmup");
module_param(l2arc_norw, int, 0644);
MODULE_PARM_DESC(l2arc_norw, "No reads during writes");
#endif
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