* 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.
*/
/*
#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>
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;
{ "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 },
#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;
*/
#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 */
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 */
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 */
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 {
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 {
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)
{
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)
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),
}
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 {
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;
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);
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);
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;
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;
* 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:
*
* 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
}
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);
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);
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.
*/
*/
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);
*
* 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.
* 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.
*/
/*
* 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
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,
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);
- }
+ mutex_exit(&l2arc_buflist_mtx);
- 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.
(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;
}
/*
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);
ARCSTAT_BUMP(arcstat_l2_feeds);
- size = l2arc_write_size(dev);
+ size = l2arc_write_size();
/*
* Evict L2ARC buffers that will be overwritten.
/*
* Write ARC buffers.
*/
- wrote = l2arc_write_buffers(spa, dev, size);
+ wrote = l2arc_write_buffers(spa, dev, size, &headroom_boost);
/*
* Calculate interval between writes.
adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
adddev->l2ad_spa = spa;
adddev->l2ad_vdev = vd;
- adddev->l2ad_write = l2arc_write_max;
- adddev->l2ad_boost = l2arc_write_boost;
adddev->l2ad_start = VDEV_LABEL_START_SIZE;
adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
adddev->l2ad_hand = adddev->l2ad_start;
adddev->l2ad_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
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_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");
projects / zfs / commitdiff