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Illumos #3137 L2ARC compression

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3137 L2ARC compression
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Dan McDonald <danmcd@nexenta.com>

References:
  illumos/illumos-gate@aad02571bc
  https://www.illumos.org/issues/3137
  http://wiki.illumos.org/display/illumos/L2ARC+Compression

Notes for Linux port:

A l2arc_nocompress module option was added to prevent the
compression of l2arc buffers regardless of how a dataset's
compression property is set.  This allows the legacy behavior
to be preserved.

Ported by: James H <james@kagisoft.co.uk>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1379
This commit is contained in:
Saso Kiselkov 2013-08-01 13:02:10 -07:00 committed by Brian Behlendorf
parent c11a12bc3b
commit 3a17a7a99a
7 changed files with 423 additions and 79 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/sys/arc.h
View File

@ -21,6 +21,7 @@
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2013 by Delphix. All rights reserved.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
*/
#ifndef _SYS_ARC_H
@ -78,6 +79,7 @@ typedef enum arc_buf_contents {
#define ARC_PREFETCH (1 << 3) /* I/O is a prefetch */
#define ARC_CACHED (1 << 4) /* I/O was already in cache */
#define ARC_L2CACHE (1 << 5) /* cache in L2ARC */
#define ARC_L2COMPRESS (1 << 6) /* compress in L2ARC */
/*
* The following breakdows of arc_size exist for kstat only.
@ -114,9 +116,9 @@ int arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
arc_done_func_t *done, void *private, int priority, int flags,
uint32_t *arc_flags, const zbookmark_t *zb);
zio_t *arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, const zio_prop_t *zp,
arc_done_func_t *ready, arc_done_func_t *done, void *private,
int priority, int zio_flags, const zbookmark_t *zb);
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 *done,
void *private, int priority, int zio_flags, const zbookmark_t *zb);
arc_prune_t *arc_add_prune_callback(arc_prune_func_t *func, void *private);
void arc_remove_prune_callback(arc_prune_t *p);

4
include/sys/dbuf.h
View File

@ -20,6 +20,7 @@
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
*/
#ifndef _SYS_DBUF_H
@ -322,6 +323,9 @@ boolean_t dbuf_is_metadata(dmu_buf_impl_t *db);
(DBUF_IS_METADATA(_db) && \
((_db)->db_objset->os_secondary_cache == ZFS_CACHE_METADATA)))
#define DBUF_IS_L2COMPRESSIBLE(_db) \
((_db)->db_objset->os_compress != ZIO_COMPRESS_OFF)
#ifdef ZFS_DEBUG
/*

3
include/sys/dmu_objset.h
View File

@ -20,6 +20,7 @@
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
*/
/* Portions Copyright 2010 Robert Milkowski */
@ -129,6 +130,8 @@ struct objset {
((os)->os_secondary_cache == ZFS_CACHE_ALL || \
(os)->os_secondary_cache == ZFS_CACHE_METADATA)
#define DMU_OS_IS_L2COMPRESSIBLE(os) ((os)->os_compress != ZIO_COMPRESS_OFF)
/* called from zpl */
int dmu_objset_hold(const char *name, void *tag, objset_t **osp);
int dmu_objset_own(const char *name, dmu_objset_type_t type,

460
module/zfs/arc.c
View File

@ -22,6 +22,7 @@
* 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.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
*/
/*
@ -128,6 +129,7 @@
#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>
@ -307,7 +309,11 @@ typedef struct arc_stats {
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;
@ -390,7 +396,11 @@ static arc_stats_t arc_stats = {
{ "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 },
@ -472,6 +482,9 @@ static arc_state_t *arc_l2c_only;
#define arc_meta_limit ARCSTAT(arcstat_meta_limit)
#define arc_meta_max ARCSTAT(arcstat_meta_max)
#define L2ARC_IS_VALID_COMPRESS(_c_) \
((_c_) == ZIO_COMPRESS_LZ4 || (_c_) == ZIO_COMPRESS_EMPTY)
typedef struct l2arc_buf_hdr l2arc_buf_hdr_t;
typedef struct arc_callback arc_callback_t;
@ -622,7 +635,12 @@ uint64_t zfs_crc64_table[256];
*/
#define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
#define L2ARC_HEADROOM 2 /* num of writes */
#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 */
@ -635,9 +653,11 @@ uint64_t zfs_crc64_table[256];
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 */
@ -648,8 +668,6 @@ 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 */
@ -670,11 +688,12 @@ 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 */
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 */
enum zio_compress l2rcb_compress; /* applied compress */
} l2arc_read_callback_t;
typedef struct l2arc_write_callback {
@ -684,8 +703,14 @@ typedef struct l2arc_write_callback {
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 */
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 */
int b_asize;
/* temporary buffer holder for in-flight compressed data */
void *b_tmp_cdata;
};
typedef struct l2arc_data_free {
@ -704,6 +729,11 @@ 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)
{
@ -1520,6 +1550,7 @@ arc_hdr_destroy(arc_buf_hdr_t *hdr)
if (l2hdr != NULL) {
list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
arc_space_return(L2HDR_SIZE, ARC_SPACE_L2HDRS);
if (hdr->b_state == arc_l2c_only)
@ -2974,6 +3005,8 @@ top:
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),
@ -3014,6 +3047,8 @@ top:
}
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 {
@ -3030,6 +3065,8 @@ top:
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;
@ -3100,20 +3137,36 @@ top:
cb->l2rcb_bp = *bp;
cb->l2rcb_zb = *zb;
cb->l2rcb_flags = zio_flags;
cb->l2rcb_compress = hdr->b_l2hdr->b_compress;
/*
* 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.
*/
rzio = zio_read_phys(pio, vd, addr, size,
buf->b_data, ZIO_CHECKSUM_OFF,
l2arc_read_done, cb, priority, zio_flags |
ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
ZIO_FLAG_DONT_PROPAGATE |
ZIO_FLAG_DONT_RETRY, B_FALSE);
if (hdr->b_l2hdr->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,
hdr->b_l2hdr->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, size);
ARCSTAT_INCR(arcstat_l2_read_bytes,
hdr->b_l2hdr->b_asize);
if (*arc_flags & ARC_NOWAIT) {
zio_nowait(rzio);
@ -3432,6 +3485,7 @@ arc_release(arc_buf_t *buf, void *tag)
buf->b_private = NULL;
if (l2hdr) {
ARCSTAT_INCR(arcstat_l2_asize, -l2hdr->b_asize);
list_remove(l2hdr->b_dev->l2ad_buflist, hdr);
kmem_free(l2hdr, sizeof (l2arc_buf_hdr_t));
arc_space_return(L2HDR_SIZE, ARC_SPACE_L2HDRS);
@ -3576,9 +3630,9 @@ arc_write_done(zio_t *zio)
zio_t *
arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, const zio_prop_t *zp,
arc_done_func_t *ready, arc_done_func_t *done, void *private,
int priority, int zio_flags, const zbookmark_t *zb)
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 *done,
void *private, int priority, int zio_flags, const zbookmark_t *zb)
{
arc_buf_hdr_t *hdr = buf->b_hdr;
arc_write_callback_t *callback;
@ -3591,6 +3645,8 @@ arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
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_PUSHPAGE);
callback->awcb_ready = ready;
callback->awcb_done = done;
@ -3985,8 +4041,12 @@ arc_fini(void)
* 2. The L2ARC attempts to cache data from the ARC before it is evicted.
* It does this by periodically scanning buffers from the eviction-end of
* the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
* not already there. It scans until a headroom of buffers is satisfied,
* which itself is a buffer for ARC eviction. The thread that does this is
* 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:
*
@ -4050,7 +4110,13 @@ arc_fini(void)
* 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
@ -4084,14 +4150,24 @@ l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
}
static uint64_t
l2arc_write_size(l2arc_dev_t *dev)
l2arc_write_size(void)
{
uint64_t size;
size = dev->l2ad_write;
/*
* 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 += dev->l2ad_boost;
size += l2arc_write_boost;
return (size);
@ -4265,12 +4341,20 @@ l2arc_write_done(zio_t *zio)
continue;
}
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);
if (zio->io_error != 0) {
/*
* Error - drop L2ARC entry.
*/
list_remove(buflist, ab);
abl2 = ab->b_l2hdr;
ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
ab->b_l2hdr = NULL;
kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
arc_space_return(L2HDR_SIZE, ARC_SPACE_L2HDRS);
@ -4323,6 +4407,13 @@ l2arc_read_done(zio_t *zio)
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.
*/
@ -4518,6 +4609,7 @@ top:
*/
if (ab->b_l2hdr != NULL) {
abl2 = ab->b_l2hdr;
ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
ab->b_l2hdr = NULL;
kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
arc_space_return(L2HDR_SIZE, ARC_SPACE_L2HDRS);
@ -4544,37 +4636,54 @@ top:
*
* 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)
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;
l2arc_buf_hdr_t *hdrl2;
list_t *list;
uint64_t passed_sz, write_sz, buf_sz, headroom;
uint64_t write_asize, write_psize, write_sz, headroom,
buf_compress_minsz;
void *buf_data;
kmutex_t *hash_lock, *list_lock = NULL;
boolean_t have_lock, full;
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 = 0;
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);
passed_sz = 0;
/*
* L2ARC fast warmup.
@ -4582,21 +4691,27 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
* Until the ARC is warm and starts to evict, read from the
* head of the ARC lists rather than the tail.
*/
headroom = target_sz * l2arc_headroom;
if (arc_warm == B_FALSE)
ab = list_head(list);
else
ab = list_tail(list);
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);
have_lock = MUTEX_HELD(hash_lock);
if (!have_lock && !mutex_tryenter(hash_lock)) {
if (!mutex_tryenter(hash_lock)) {
/*
* Skip this buffer rather than waiting.
*/
@ -4642,17 +4757,29 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
/*
* Create and add a new L2ARC header.
*/
hdrl2 = kmem_zalloc(sizeof (l2arc_buf_hdr_t),
KM_PUSHPAGE);
hdrl2->b_dev = dev;
hdrl2->b_daddr = dev->l2ad_hand;
l2hdr = kmem_zalloc(sizeof (l2arc_buf_hdr_t),
KM_PUSHPAGE);
l2hdr->b_dev = dev;
arc_space_consume(L2HDR_SIZE, ARC_SPACE_L2HDRS);
ab->b_flags |= ARC_L2_WRITING;
ab->b_l2hdr = hdrl2;
list_insert_head(dev->l2ad_buflist, ab);
buf_data = ab->b_buf->b_data;
/*
* 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;
buf_sz = ab->b_size;
ab->b_l2hdr = l2hdr;
list_insert_head(dev->l2ad_buflist, ab);
/*
* Compute and store the buffer cksum before
@ -4663,6 +4790,64 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
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;
/* 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,
@ -4672,33 +4857,24 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
zio_t *, wzio);
(void) zio_nowait(wzio);
write_asize += buf_sz;
/*
* Keep the clock hand suitably device-aligned.
*/
buf_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
write_sz += buf_sz;
dev->l2ad_hand += buf_sz;
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(list_lock);
if (full == B_TRUE)
break;
}
mutex_exit(&l2arc_buflist_mtx);
if (pio == NULL) {
ASSERT0(write_sz);
kmem_cache_free(hdr_cache, head);
return (0);
}
ASSERT3U(write_sz, <=, target_sz);
ASSERT3U(write_asize, <=, target_sz);
ARCSTAT_BUMP(arcstat_l2_writes_sent);
ARCSTAT_INCR(arcstat_l2_write_bytes, write_sz);
ARCSTAT_INCR(arcstat_l2_write_bytes, write_asize);
ARCSTAT_INCR(arcstat_l2_size, write_sz);
vdev_space_update(dev->l2ad_vdev, write_sz, 0, 0);
ARCSTAT_INCR(arcstat_l2_asize, write_asize);
vdev_space_update(dev->l2ad_vdev, write_psize, 0, 0);
/*
* Bump device hand to the device start if it is approaching the end.
@ -4716,7 +4892,153 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
(void) zio_wait(pio);
dev->l2ad_writing = B_FALSE;
return (write_sz);
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;
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);
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 = 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;
if (l2hdr->b_compress == ZIO_COMPRESS_LZ4) {
/*
* 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;
}
/*
@ -4731,6 +5053,7 @@ l2arc_feed_thread(void)
spa_t *spa;
uint64_t size, wrote;
clock_t begin, next = ddi_get_lbolt();
boolean_t headroom_boost = B_FALSE;
CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
@ -4791,7 +5114,7 @@ l2arc_feed_thread(void)
ARCSTAT_BUMP(arcstat_l2_feeds);
size = l2arc_write_size(dev);
size = l2arc_write_size();
/*
* Evict L2ARC buffers that will be overwritten.
@ -4801,7 +5124,7 @@ l2arc_feed_thread(void)
/*
* Write ARC buffers.
*/
wrote = l2arc_write_buffers(spa, dev, size);
wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost);
/*
* Calculate interval between writes.
@ -4849,8 +5172,6 @@ l2arc_add_vdev(spa_t *spa, vdev_t *vd)
adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
adddev->l2ad_spa = spa;
adddev->l2ad_vdev = vd;
adddev->l2ad_write = l2arc_write_max;
adddev->l2ad_boost = l2arc_write_boost;
adddev->l2ad_start = VDEV_LABEL_START_SIZE;
adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
adddev->l2ad_hand = adddev->l2ad_start;
@ -4858,7 +5179,6 @@ l2arc_add_vdev(spa_t *spa, vdev_t *vd)
adddev->l2ad_first = B_TRUE;
adddev->l2ad_writing = B_FALSE;
list_link_init(&adddev->l2ad_node);
ASSERT3U(adddev->l2ad_write, >, 0);
/*
* This is a list of all ARC buffers that are still valid on the
@ -5030,6 +5350,9 @@ 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");
@ -5039,6 +5362,9 @@ 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");

10
module/zfs/dbuf.c
View File

@ -22,6 +22,7 @@
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
* Copyright (c) 2012 by Delphix. All rights reserved.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
*/
#include <sys/zfs_context.h>
@ -614,6 +615,8 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
if (DBUF_IS_L2CACHEABLE(db))
aflags |= ARC_L2CACHE;
if (DBUF_IS_L2COMPRESSIBLE(db))
aflags |= ARC_L2COMPRESS;
SET_BOOKMARK(&zb, db->db_objset->os_dsl_dataset ?
db->db_objset->os_dsl_dataset->ds_object : DMU_META_OBJSET,
@ -2822,9 +2825,10 @@ dbuf_write(dbuf_dirty_record_t *dr, arc_buf_t *data, dmu_tx_t *tx)
} else {
ASSERT(arc_released(data));
dr->dr_zio = arc_write(zio, os->os_spa, txg,
db->db_blkptr, data, DBUF_IS_L2CACHEABLE(db), &zp,
dbuf_write_ready, dbuf_write_done, db,
ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_MUSTSUCCEED, &zb);
db->db_blkptr, data, DBUF_IS_L2CACHEABLE(db),
DBUF_IS_L2COMPRESSIBLE(db), &zp, dbuf_write_ready,
dbuf_write_done, db, ZIO_PRIORITY_ASYNC_WRITE,
ZIO_FLAG_MUSTSUCCEED, &zb);
}
}

7
module/zfs/dmu.c
View File

@ -21,6 +21,7 @@
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012 by Delphix. All rights reserved.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
*/
#include <sys/dmu.h>
@ -1653,9 +1654,9 @@ dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd)
dsa->dsa_tx = NULL;
zio_nowait(arc_write(pio, os->os_spa, txg,
bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db), &zp,
dmu_sync_ready, dmu_sync_done, dsa,
ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL | ZIO_FLAG_FASTWRITE, &zb));
bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db),
DBUF_IS_L2COMPRESSIBLE(db), &zp, dmu_sync_ready, dmu_sync_done,
dsa, ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL | ZIO_FLAG_FASTWRITE, &zb));
return (0);
}

10
module/zfs/dmu_objset.c
View File

@ -20,6 +20,7 @@
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
*/
/* Portions Copyright 2010 Robert Milkowski */
@ -274,6 +275,8 @@ dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
if (DMU_OS_IS_L2CACHEABLE(os))
aflags |= ARC_L2CACHE;
if (DMU_OS_IS_L2COMPRESSIBLE(os))
aflags |= ARC_L2COMPRESS;
dprintf_bp(os->os_rootbp, "reading %s", "");
err = arc_read(NULL, spa, os->os_rootbp,
@ -1119,9 +1122,10 @@ dmu_objset_sync(objset_t *os, zio_t *pio, dmu_tx_t *tx)
dmu_write_policy(os, NULL, 0, 0, &zp);
zio = arc_write(pio, os->os_spa, tx->tx_txg,
os->os_rootbp, os->os_phys_buf, DMU_OS_IS_L2CACHEABLE(os), &zp,
dmu_objset_write_ready, dmu_objset_write_done, os,
ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_MUSTSUCCEED, &zb);
os->os_rootbp, os->os_phys_buf, DMU_OS_IS_L2CACHEABLE(os),
DMU_OS_IS_L2COMPRESSIBLE(os), &zp, dmu_objset_write_ready,
dmu_objset_write_done, os, ZIO_PRIORITY_ASYNC_WRITE,
ZIO_FLAG_MUSTSUCCEED, &zb);
/*
* Sync special dnodes - the parent IO for the sync is the root block