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arc.c
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arc.c
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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 2011 Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 2011 by Delphix. All rights reserved.
*/
/*
* DVA-based Adjustable Replacement Cache
*
* While much of the theory of operation used here is
* based on the self-tuning, low overhead replacement cache
* presented by Megiddo and Modha at FAST 2003, there are some
* significant differences:
*
* 1. The Megiddo and Modha model assumes any page is evictable.
* Pages in its cache cannot be "locked" into memory. This makes
* the eviction algorithm simple: evict the last page in the list.
* This also make the performance characteristics easy to reason
* about. Our cache is not so simple. At any given moment, some
* subset of the blocks in the cache are un-evictable because we
* have handed out a reference to them. Blocks are only evictable
* when there are no external references active. This makes
* eviction far more problematic: we choose to evict the evictable
* blocks that are the "lowest" in the list.
*
* There are times when it is not possible to evict the requested
* space. In these circumstances we are unable to adjust the cache
* size. To prevent the cache growing unbounded at these times we
* implement a "cache throttle" that slows the flow of new data
* into the cache until we can make space available.
*
* 2. The Megiddo and Modha model assumes a fixed cache size.
* Pages are evicted when the cache is full and there is a cache
* miss. Our model has a variable sized cache. It grows with
* high use, but also tries to react to memory pressure from the
* operating system: decreasing its size when system memory is
* tight.
*
* 3. The Megiddo and Modha model assumes a fixed page size. All
* elements of the cache are therefor exactly the same size. So
* when adjusting the cache size following a cache miss, its simply
* a matter of choosing a single page to evict. In our model, we
* have variable sized cache blocks (rangeing from 512 bytes to
* 128K bytes). We therefor choose a set of blocks to evict to make
* space for a cache miss that approximates as closely as possible
* the space used by the new block.
*
* See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
* by N. Megiddo & D. Modha, FAST 2003
*/
/*
* The locking model:
*
* A new reference to a cache buffer can be obtained in two
* ways: 1) via a hash table lookup using the DVA as a key,
* or 2) via one of the ARC lists. The arc_read() interface
* uses method 1, while the internal arc algorithms for
* adjusting the cache use method 2. We therefor provide two
* types of locks: 1) the hash table lock array, and 2) the
* arc list locks.
*
* Buffers do not have their own 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_buf_evict()
* 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/zfs_context.h>
#include <sys/arc.h>
#include <sys/vdev.h>
#include <sys/vdev_impl.h>
#ifdef _KERNEL
#include <sys/vmsystm.h>
#include <vm/anon.h>
#include <sys/fs/swapnode.h>
#include <sys/zpl.h>
#endif
#include <sys/callb.h>
#include <sys/kstat.h>
#include <sys/dmu_tx.h>
#include <zfs_fletcher.h>
static kmutex_t arc_reclaim_thr_lock;
static kcondvar_t arc_reclaim_thr_cv; /* used to signal reclaim thr */
static uint8_t arc_thread_exit;
/* number of bytes to prune from caches when at arc_meta_limit is reached */
uint_t arc_meta_prune = 1048576;
typedef enum arc_reclaim_strategy {
ARC_RECLAIM_AGGR, /* Aggressive reclaim strategy */
ARC_RECLAIM_CONS /* Conservative reclaim strategy */
} arc_reclaim_strategy_t;
/* number of seconds before growing cache again */
static int arc_grow_retry = 5;
/* expiration time for arc_no_grow */
static clock_t arc_grow_time = 0;
/* shift of arc_c for calculating both min and max arc_p */
static int arc_p_min_shift = 4;
/* log2(fraction of arc to reclaim) */
static int arc_shrink_shift = 5;
/*
* minimum lifespan of a prefetch block in clock ticks
* (initialized in arc_init())
*/
static int arc_min_prefetch_lifespan;
static int arc_dead;
/*
* The arc has filled available memory and has now warmed up.
*/
static boolean_t arc_warm;
/*
* These tunables are for performance analysis.
*/
unsigned long zfs_arc_max = 0;
unsigned long zfs_arc_min = 0;
unsigned long zfs_arc_meta_limit = 0;
int zfs_arc_grow_retry = 0;
int zfs_arc_shrink_shift = 0;
int zfs_arc_p_min_shift = 0;
int zfs_arc_memory_throttle_disable = 1;
int zfs_disable_dup_eviction = 0;
int zfs_arc_meta_prune = 0;
/*
* Note that buffers can be in one of 6 states:
* ARC_anon - anonymous (discussed below)
* ARC_mru - recently used, currently cached
* ARC_mru_ghost - recentely used, no longer in cache
* ARC_mfu - frequently used, currently cached
* ARC_mfu_ghost - frequently used, no longer in cache
* ARC_l2c_only - exists in L2ARC but not other states
* When there are no active references to the buffer, they are
* are linked onto a list in one of these arc states. These are
* the only buffers that can be evicted or deleted. Within each
* state there are multiple lists, one for meta-data and one for
* non-meta-data. Meta-data (indirect blocks, blocks of dnodes,
* etc.) is tracked separately so that it can be managed more
* explicitly: favored over data, limited explicitly.
*
* Anonymous buffers are buffers that are not associated with
* a DVA. These are buffers that hold dirty block copies
* before they are written to stable storage. By definition,
* they are "ref'd" and are considered part of arc_mru
* that cannot be freed. Generally, they will aquire a DVA
* as they are written and migrate onto the arc_mru list.
*
* The ARC_l2c_only state is for buffers that are in the second
* level ARC but no longer in any of the ARC_m* lists. The second
* level ARC itself may also contain buffers that are in any of
* the ARC_m* states - meaning that a buffer can exist in two
* places. The reason for the ARC_l2c_only state is to keep the
* buffer header in the hash table, so that reads that hit the
* second level ARC benefit from these fast lookups.
*/
typedef struct arc_state {
list_t arcs_list[ARC_BUFC_NUMTYPES]; /* list of evictable buffers */
uint64_t arcs_lsize[ARC_BUFC_NUMTYPES]; /* amount of evictable data */
uint64_t arcs_size; /* total amount of data in this state */
kmutex_t arcs_mtx;
} arc_state_t;
/* The 6 states: */
static arc_state_t ARC_anon;
static arc_state_t ARC_mru;
static arc_state_t ARC_mru_ghost;
static arc_state_t ARC_mfu;
static arc_state_t ARC_mfu_ghost;
static arc_state_t ARC_l2c_only;
typedef struct arc_stats {
kstat_named_t arcstat_hits;
kstat_named_t arcstat_misses;
kstat_named_t arcstat_demand_data_hits;
kstat_named_t arcstat_demand_data_misses;
kstat_named_t arcstat_demand_metadata_hits;
kstat_named_t arcstat_demand_metadata_misses;
kstat_named_t arcstat_prefetch_data_hits;
kstat_named_t arcstat_prefetch_data_misses;
kstat_named_t arcstat_prefetch_metadata_hits;
kstat_named_t arcstat_prefetch_metadata_misses;
kstat_named_t arcstat_mru_hits;
kstat_named_t arcstat_mru_ghost_hits;
kstat_named_t arcstat_mfu_hits;
kstat_named_t arcstat_mfu_ghost_hits;
kstat_named_t arcstat_deleted;
kstat_named_t arcstat_recycle_miss;
kstat_named_t arcstat_mutex_miss;
kstat_named_t arcstat_evict_skip;
kstat_named_t arcstat_evict_l2_cached;
kstat_named_t arcstat_evict_l2_eligible;
kstat_named_t arcstat_evict_l2_ineligible;
kstat_named_t arcstat_hash_elements;
kstat_named_t arcstat_hash_elements_max;
kstat_named_t arcstat_hash_collisions;
kstat_named_t arcstat_hash_chains;
kstat_named_t arcstat_hash_chain_max;
kstat_named_t arcstat_p;
kstat_named_t arcstat_c;
kstat_named_t arcstat_c_min;
kstat_named_t arcstat_c_max;
kstat_named_t arcstat_size;
kstat_named_t arcstat_hdr_size;
kstat_named_t arcstat_data_size;
kstat_named_t arcstat_other_size;
kstat_named_t arcstat_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_abort_lowmem;
kstat_named_t arcstat_l2_cksum_bad;
kstat_named_t arcstat_l2_io_error;
kstat_named_t arcstat_l2_size;
kstat_named_t arcstat_l2_hdr_size;
kstat_named_t arcstat_memory_throttle_count;
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 },
{ "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_abort_lowmem", KSTAT_DATA_UINT64 },
{ "l2_cksum_bad", KSTAT_DATA_UINT64 },
{ "l2_io_error", KSTAT_DATA_UINT64 },
{ "l2_size", KSTAT_DATA_UINT64 },
{ "l2_hdr_size", KSTAT_DATA_UINT64 },
{ "memory_throttle_count", KSTAT_DATA_UINT64 },
{ "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_used ARCSTAT(arcstat_meta_used)
#define arc_meta_limit ARCSTAT(arcstat_meta_limit)
#define arc_meta_max ARCSTAT(arcstat_meta_max)
typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
typedef struct arc_callback arc_callback_t;
struct arc_callback {
void *acb_private;
arc_done_func_t *acb_done;
arc_buf_t *acb_buf;
zio_t *acb_zio_dummy;
arc_callback_t *acb_next;
};
typedef struct arc_write_callback arc_write_callback_t;
struct arc_write_callback {
void *awcb_private;
arc_done_func_t *awcb_ready;
arc_done_func_t *awcb_done;
arc_buf_t *awcb_buf;
};
struct arc_buf_hdr {
/* protected by hash lock */
dva_t b_dva;
uint64_t b_birth;
uint64_t b_cksum0;
kmutex_t b_freeze_lock;
zio_cksum_t *b_freeze_cksum;
void *b_thawed;
arc_buf_hdr_t *b_hash_next;
arc_buf_t *b_buf;
uint32_t b_flags;
uint32_t b_datacnt;
arc_callback_t *b_acb;
kcondvar_t b_cv;
/* immutable */
arc_buf_contents_t b_type;
uint64_t b_size;
uint64_t b_spa;
/* protected by arc state mutex */
arc_state_t *b_state;
list_node_t b_arc_node;
/* updated atomically */
clock_t b_arc_access;
/* self protecting */
refcount_t b_refcnt;
l2arc_buf_hdr_t *b_l2hdr;
list_node_t b_l2node;
};
static 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);
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 256
typedef struct buf_hash_table {
uint64_t ht_mask;
arc_buf_hdr_t **ht_table;
struct ht_lock ht_locks[BUF_LOCKS];
} buf_hash_table_t;
static buf_hash_table_t buf_hash_table;
#define BUF_HASH_INDEX(spa, dva, birth) \
(buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
#define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
#define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
#define HDR_LOCK(hdr) \
(BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
uint64_t zfs_crc64_table[256];
/*
* Level 2 ARC
*/
#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
#define L2ARC_HEADROOM 2 /* num of writes */
#define L2ARC_FEED_SECS 1 /* caching interval secs */
#define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
#define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
#define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
/*
* L2ARC Performance Tunables
*/
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_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_feed_again = B_TRUE; /* turbo warmup */
int l2arc_norw = B_TRUE; /* no reads during writes */
/*
* L2ARC Internals
*/
typedef struct l2arc_dev {
vdev_t *l2ad_vdev; /* vdev */
spa_t *l2ad_spa; /* spa */
uint64_t l2ad_hand; /* next write location */
uint64_t l2ad_write; /* desired write size, bytes */
uint64_t l2ad_boost; /* warmup write boost, bytes */
uint64_t l2ad_start; /* first addr on device */
uint64_t l2ad_end; /* last addr on device */
uint64_t l2ad_evict; /* last addr eviction reached */
boolean_t l2ad_first; /* first sweep through */
boolean_t l2ad_writing; /* currently writing */
list_t *l2ad_buflist; /* buffer list */
list_node_t l2ad_node; /* device list node */
} l2arc_dev_t;
static list_t L2ARC_dev_list; /* device list */
static list_t *l2arc_dev_list; /* device list pointer */
static kmutex_t l2arc_dev_mtx; /* device list mutex */
static l2arc_dev_t *l2arc_dev_last; /* last device used */
static kmutex_t l2arc_buflist_mtx; /* mutex for all buflists */
static list_t L2ARC_free_on_write; /* free after write buf list */
static list_t *l2arc_free_on_write; /* free after write list ptr */
static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
static uint64_t l2arc_ndev; /* number of devices */
typedef struct l2arc_read_callback {
arc_buf_t *l2rcb_buf; /* read buffer */
spa_t *l2rcb_spa; /* spa */
blkptr_t l2rcb_bp; /* original blkptr */
zbookmark_t l2rcb_zb; /* original bookmark */
int l2rcb_flags; /* original flags */
} l2arc_read_callback_t;
typedef struct l2arc_write_callback {
l2arc_dev_t *l2wcb_dev; /* device info */
arc_buf_hdr_t *l2wcb_head; /* head of write buflist */
} l2arc_write_callback_t;
struct l2arc_buf_hdr {
/* protected by arc_buf_hdr mutex */
l2arc_dev_t *b_dev; /* L2ARC device */
uint64_t b_daddr; /* disk address, offset byte */
};
typedef struct l2arc_data_free {
/* protected by l2arc_free_on_write_mtx */
void *l2df_data;
size_t l2df_size;
void (*l2df_func)(void *, size_t);
list_node_t l2df_list_node;
} l2arc_data_free_t;
static kmutex_t l2arc_feed_thr_lock;
static kcondvar_t l2arc_feed_thr_cv;
static uint8_t l2arc_thread_exit;
static void l2arc_read_done(zio_t *zio);
static void l2arc_hdr_stat_add(void);
static void l2arc_hdr_stat_remove(void);
static uint64_t
buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
{
uint8_t *vdva = (uint8_t *)dva;
uint64_t crc = -1ULL;
int i;
ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
for (i = 0; i < sizeof (dva_t); i++)
crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ vdva[i]) & 0xFF];
crc ^= (spa>>8) ^ birth;
return (crc);
}
#define BUF_EMPTY(buf) \
((buf)->b_dva.dva_word[0] == 0 && \
(buf)->b_dva.dva_word[1] == 0 && \
(buf)->b_birth == 0)
#define BUF_EQUAL(spa, dva, birth, buf) \
((buf)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
((buf)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
((buf)->b_birth == birth) && ((buf)->b_spa == spa)
static void
buf_discard_identity(arc_buf_hdr_t *hdr)
{
hdr->b_dva.dva_word[0] = 0;
hdr->b_dva.dva_word[1] = 0;
hdr->b_birth = 0;
hdr->b_cksum0 = 0;
}
static arc_buf_hdr_t *
buf_hash_find(uint64_t spa, const dva_t *dva, uint64_t birth, kmutex_t **lockp)
{
uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
arc_buf_hdr_t *buf;
mutex_enter(hash_lock);
for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
buf = buf->b_hash_next) {
if (BUF_EQUAL(spa, dva, birth, buf)) {
*lockp = hash_lock;
return (buf);
}
}
mutex_exit(hash_lock);
*lockp = NULL;
return (NULL);
}
/*
* Insert an entry into the hash table. If there is already an element
* equal to elem in the hash table, then the already existing element
* will be returned and the new element will not be inserted.
* Otherwise returns NULL.
*/
static arc_buf_hdr_t *
buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
{
uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
arc_buf_hdr_t *fbuf;
uint32_t i;
ASSERT(!HDR_IN_HASH_TABLE(buf));
*lockp = hash_lock;
mutex_enter(hash_lock);
for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
fbuf = fbuf->b_hash_next, i++) {
if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
return (fbuf);
}
buf->b_hash_next = buf_hash_table.ht_table[idx];
buf_hash_table.ht_table[idx] = buf;
buf->b_flags |= ARC_IN_HASH_TABLE;
/* collect some hash table performance data */
if (i > 0) {
ARCSTAT_BUMP(arcstat_hash_collisions);
if (i == 1)
ARCSTAT_BUMP(arcstat_hash_chains);
ARCSTAT_MAX(arcstat_hash_chain_max, i);
}
ARCSTAT_BUMP(arcstat_hash_elements);
ARCSTAT_MAXSTAT(arcstat_hash_elements);
return (NULL);
}
static void
buf_hash_remove(arc_buf_hdr_t *buf)
{
arc_buf_hdr_t *fbuf, **bufp;
uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
ASSERT(HDR_IN_HASH_TABLE(buf));
bufp = &buf_hash_table.ht_table[idx];
while ((fbuf = *bufp) != buf) {
ASSERT(fbuf != NULL);
bufp = &fbuf->b_hash_next;
}
*bufp = buf->b_hash_next;
buf->b_hash_next = NULL;
buf->b_flags &= ~ARC_IN_HASH_TABLE;
/* collect some hash table performance data */
ARCSTAT_BUMPDOWN(arcstat_hash_elements);
if (buf_hash_table.ht_table[idx] &&
buf_hash_table.ht_table[idx]->b_hash_next == NULL)
ARCSTAT_BUMPDOWN(arcstat_hash_chains);
}
/*
* Global data structures and functions for the buf kmem cache.
*/
static kmem_cache_t *hdr_cache;
static kmem_cache_t *buf_cache;
static void
buf_fini(void)
{
int i;
#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);
}
/*
* 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);
rw_init(&buf->b_data_lock, NULL, RW_DEFAULT, NULL);
arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
return (0);
}
/*
* Destructor callback - called when a cached buf is
* no longer required.
*/
/* ARGSUSED */
static void
hdr_dest(void *vbuf, void *unused)
{
arc_buf_hdr_t *buf = vbuf;
ASSERT(BUF_EMPTY(buf));
refcount_destroy(&buf->b_refcnt);
cv_destroy(&buf->b_cv);
mutex_destroy(&buf->b_freeze_lock);
arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
}
/* ARGSUSED */
static void
buf_dest(void *vbuf, void *unused)
{
arc_buf_t *buf = vbuf;
mutex_destroy(&buf->b_evict_lock);
rw_destroy(&buf->b_data_lock);
arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
}
static void
buf_init(void)
{
uint64_t *ct;
uint64_t hsize = 1ULL << 12;
int i, j;
/*
* The hash table is big enough to fill all of physical memory
* with an average 64K block size. The table will take up
* totalmem*sizeof(void*)/64K (eg. 128KB/GB with 8-byte pointers).
*/
while (hsize * 65536 < physmem * PAGESIZE)
hsize <<= 1;
retry:
buf_hash_table.ht_mask = hsize - 1;
#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);
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);