Author: mav
Date: Sat Oct 3 11:35:18 2015
New Revision: 288594
URL: https://svnweb.freebsd.org/changeset/base/288594
Log:
MFC r287702: 5987 zfs prefetch code needs work
Rewrite the ZFS prefetch code to detect only forward, sequential
streams.
The following kstats have been added:
kstat.zfs.misc.arcstats.sync_wait_for_async
How many sync reads have waited for async read
to complete. (less is better)
kstat.zfs.misc.arcstats.demand_hit_predictive_prefetch
How many demand read didn't have to wait for I/O
because of predictive prefetch. (more is better)
zfetch kstats have been similified to hits, misses, and max_streams,
with max_streams representing times when we were not able to create
new stream because we already have the maximum number of sequences
for a file.
The sysctl variable/loader tunable vfs.zfs.zfetch.block_cap have been
replaced by vfs.zfs.zfetch.max_distance, which controls maximum bytes
to prefetch per stream.
illumos/illumos-gate@cf6106c8a0d6598b045811f9650d66e07eb332af
Illumos ZFS issues:
5987 zfs prefetch code needs work
https://www.illumos.org/issues/5987
Modified:
stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c
stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c
stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c
stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dnode.c
stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/arc.h
stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/dmu.h
stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/dmu_zfetch.h
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
==============================================================================
--- stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c Sat Oct
3 11:27:23 2015 (r288593)
+++ stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c Sat Oct
3 11:35:18 2015 (r288594)
@@ -213,7 +213,7 @@ static int arc_min_prefetch_lifespan;
int arc_lotsfree_percent = 10;
static int arc_dead;
-extern int zfs_prefetch_disable;
+extern boolean_t zfs_prefetch_disable;
/*
* The arc has filled available memory and has now warmed up.
@@ -585,6 +585,8 @@ typedef struct arc_stats {
kstat_named_t arcstat_meta_limit;
kstat_named_t arcstat_meta_max;
kstat_named_t arcstat_meta_min;
+ kstat_named_t arcstat_sync_wait_for_async;
+ kstat_named_t arcstat_demand_hit_predictive_prefetch;
} arc_stats_t;
static arc_stats_t arc_stats = {
@@ -683,7 +685,9 @@ static arc_stats_t arc_stats = {
{ "arc_meta_used", KSTAT_DATA_UINT64 },
{ "arc_meta_limit", KSTAT_DATA_UINT64 },
{ "arc_meta_max", KSTAT_DATA_UINT64 },
- { "arc_meta_min", KSTAT_DATA_UINT64 }
+ { "arc_meta_min", KSTAT_DATA_UINT64 },
+ { "sync_wait_for_async", KSTAT_DATA_UINT64 },
+ { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 },
};
#define ARCSTAT(stat) (arc_stats.stat.value.ui64)
@@ -4253,6 +4257,36 @@ top:
if (HDR_IO_IN_PROGRESS(hdr)) {
+ if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
+ priority == ZIO_PRIORITY_SYNC_READ) {
+ /*
+ * This sync read must wait for an
+ * in-progress async read (e.g. a predictive
+ * prefetch). Async reads are queued
+ * separately at the vdev_queue layer, so
+ * this is a form of priority inversion.
+ * Ideally, we would "inherit" the demand
+ * i/o's priority by moving the i/o from
+ * the async queue to the synchronous queue,
+ * but there is currently no mechanism to do
+ * so. Track this so that we can evaluate
+ * the magnitude of this potential performance
+ * problem.
+ *
+ * Note that if the prefetch i/o is already
+ * active (has been issued to the device),
+ * the prefetch improved performance, because
+ * we issued it sooner than we would have
+ * without the prefetch.
+ */
+ DTRACE_PROBE1(arc__sync__wait__for__async,
+ arc_buf_hdr_t *, hdr);
+ ARCSTAT_BUMP(arcstat_sync_wait_for_async);
+ }
+ if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
+ hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH;
+ }
+
if (*arc_flags & ARC_FLAG_WAIT) {
cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
mutex_exit(hash_lock);
@@ -4261,7 +4295,7 @@ top:
ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
if (done) {
- arc_callback_t *acb = NULL;
+ arc_callback_t *acb = NULL;
acb = kmem_zalloc(sizeof (arc_callback_t),
KM_SLEEP);
@@ -4286,6 +4320,19 @@ top:
hdr->b_l1hdr.b_state == arc_mfu);
if (done) {
+ if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
+ /*
+ * This is a demand read which does not have to
+ * wait for i/o because we did a predictive
+ * prefetch i/o for it, which has completed.
+ */
+ DTRACE_PROBE1(
+ arc__demand__hit__predictive__prefetch,
+ arc_buf_hdr_t *, hdr);
+ ARCSTAT_BUMP(
+ arcstat_demand_hit_predictive_prefetch);
+ hdr->b_flags &= ~ARC_FLAG_PREDICTIVE_PREFETCH;
+ }
add_reference(hdr, hash_lock, private);
/*
* If this block is already in use, create a new
@@ -4348,12 +4395,16 @@ top:
goto top; /* restart the IO request */
}
- /* if this is a prefetch, we don't have a reference */
- if (*arc_flags & ARC_FLAG_PREFETCH) {
+ /*
+ * If there is a callback, we pass our reference to
+ * it; otherwise we remove our reference.
+ */
+ if (done == NULL) {
(void) remove_reference(hdr, hash_lock,
private);
- hdr->b_flags |= ARC_FLAG_PREFETCH;
}
+ if (*arc_flags & ARC_FLAG_PREFETCH)
+ hdr->b_flags |= ARC_FLAG_PREFETCH;
if (*arc_flags & ARC_FLAG_L2CACHE)
hdr->b_flags |= ARC_FLAG_L2CACHE;
if (*arc_flags & ARC_FLAG_L2COMPRESS)
@@ -4376,11 +4427,13 @@ top:
ASSERT(refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
- /* if this is a prefetch, we don't have a reference */
+ /*
+ * If there is a callback, we pass a reference to it.
+ */
+ if (done != NULL)
+ add_reference(hdr, hash_lock, private);
if (*arc_flags & ARC_FLAG_PREFETCH)
hdr->b_flags |= ARC_FLAG_PREFETCH;
- else
- add_reference(hdr, hash_lock, private);
if (*arc_flags & ARC_FLAG_L2CACHE)
hdr->b_flags |= ARC_FLAG_L2CACHE;
if (*arc_flags & ARC_FLAG_L2COMPRESS)
@@ -4398,6 +4451,8 @@ top:
arc_access(hdr, hash_lock);
}
+ if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH)
+ hdr->b_flags |= ARC_FLAG_PREDICTIVE_PREFETCH;
ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
@@ -4440,6 +4495,11 @@ top:
curthread->td_ru.ru_inblock++;
#endif
+ if (priority == ZIO_PRIORITY_ASYNC_READ)
+ hdr->b_flags |= ARC_FLAG_PRIO_ASYNC_READ;
+ else
+ hdr->b_flags &= ~ARC_FLAG_PRIO_ASYNC_READ;
+
if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
/*
* Read from the L2ARC if the following are true:
Modified: stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c
==============================================================================
--- stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Sat Oct
3 11:27:23 2015 (r288593)
+++ stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Sat Oct
3 11:35:18 2015 (r288594)
@@ -613,7 +613,7 @@ dbuf_read_done(zio_t *zio, arc_buf_t *bu
}
static void
-dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
+dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
{
dnode_t *dn;
zbookmark_phys_t zb;
@@ -659,7 +659,6 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t
db->db.db_size, db, type));
bzero(db->db.db_data, db->db.db_size);
db->db_state = DB_CACHED;
- *flags |= DB_RF_CACHED;
mutex_exit(&db->db_mtx);
return;
}
@@ -682,10 +681,8 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t
(void) arc_read(zio, db->db_objset->os_spa, db->db_blkptr,
dbuf_read_done, db, ZIO_PRIORITY_SYNC_READ,
- (*flags & DB_RF_CANFAIL) ? ZIO_FLAG_CANFAIL : ZIO_FLAG_MUSTSUCCEED,
+ (flags & DB_RF_CANFAIL) ? ZIO_FLAG_CANFAIL : ZIO_FLAG_MUSTSUCCEED,
&aflags, &zb);
- if (aflags & ARC_FLAG_CACHED)
- *flags |= DB_RF_CACHED;
}
int
@@ -718,8 +715,7 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio
if (db->db_state == DB_CACHED) {
mutex_exit(&db->db_mtx);
if (prefetch)
- dmu_zfetch(&dn->dn_zfetch, db->db.db_offset,
- db->db.db_size, TRUE);
+ dmu_zfetch(&dn->dn_zfetch, db->db_blkid, 1);
if ((flags & DB_RF_HAVESTRUCT) == 0)
rw_exit(&dn->dn_struct_rwlock);
DB_DNODE_EXIT(db);
@@ -728,13 +724,12 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio
if (zio == NULL)
zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CANFAIL);
- dbuf_read_impl(db, zio, &flags);
+ dbuf_read_impl(db, zio, flags);
/* dbuf_read_impl has dropped db_mtx for us */
if (prefetch)
- dmu_zfetch(&dn->dn_zfetch, db->db.db_offset,
- db->db.db_size, flags & DB_RF_CACHED);
+ dmu_zfetch(&dn->dn_zfetch, db->db_blkid, 1);
if ((flags & DB_RF_HAVESTRUCT) == 0)
rw_exit(&dn->dn_struct_rwlock);
@@ -753,8 +748,7 @@ dbuf_read(dmu_buf_impl_t *db, zio_t *zio
*/
mutex_exit(&db->db_mtx);
if (prefetch)
- dmu_zfetch(&dn->dn_zfetch, db->db.db_offset,
- db->db.db_size, TRUE);
+ dmu_zfetch(&dn->dn_zfetch, db->db_blkid, 1);
if ((flags & DB_RF_HAVESTRUCT) == 0)
rw_exit(&dn->dn_struct_rwlock);
DB_DNODE_EXIT(db);
@@ -2054,6 +2048,9 @@ dbuf_prefetch(dnode_t *dn, int64_t level
ASSERT(blkid != DMU_BONUS_BLKID);
ASSERT(RW_LOCK_HELD(&dn->dn_struct_rwlock));
+ if (blkid > dn->dn_maxblkid)
+ return;
+
if (dnode_block_freed(dn, blkid))
return;
Modified: stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c
==============================================================================
--- stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c Sat Oct
3 11:27:23 2015 (r288593)
+++ stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c Sat Oct
3 11:35:18 2015 (r288594)
@@ -20,7 +20,7 @@
*/
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
*/
/* Copyright (c) 2013 by Saso Kiselkov. All rights reserved. */
/* Copyright (c) 2013, Joyent, Inc. All rights reserved. */
@@ -390,7 +390,7 @@ dmu_spill_hold_by_bonus(dmu_buf_t *bonus
*/
static int
dmu_buf_hold_array_by_dnode(dnode_t *dn, uint64_t offset, uint64_t length,
- int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp, uint32_t flags)
+ boolean_t read, void *tag, int *numbufsp, dmu_buf_t ***dbpp, uint32_t
flags)
{
dmu_buf_t **dbp;
uint64_t blkid, nblks, i;
@@ -400,15 +400,19 @@ dmu_buf_hold_array_by_dnode(dnode_t *dn,
ASSERT(length <= DMU_MAX_ACCESS);
- dbuf_flags = DB_RF_CANFAIL | DB_RF_NEVERWAIT | DB_RF_HAVESTRUCT;
- if (flags & DMU_READ_NO_PREFETCH || length > zfetch_array_rd_sz)
- dbuf_flags |= DB_RF_NOPREFETCH;
+ /*
+ * Note: We directly notify the prefetch code of this read, so that
+ * we can tell it about the multi-block read. dbuf_read() only knows
+ * about the one block it is accessing.
+ */
+ dbuf_flags = DB_RF_CANFAIL | DB_RF_NEVERWAIT | DB_RF_HAVESTRUCT |
+ DB_RF_NOPREFETCH;
rw_enter(&dn->dn_struct_rwlock, RW_READER);
if (dn->dn_datablkshift) {
int blkshift = dn->dn_datablkshift;
- nblks = (P2ROUNDUP(offset+length, 1ULL<<blkshift) -
- P2ALIGN(offset, 1ULL<<blkshift)) >> blkshift;
+ nblks = (P2ROUNDUP(offset + length, 1ULL << blkshift) -
+ P2ALIGN(offset, 1ULL << blkshift)) >> blkshift;
} else {
if (offset + length > dn->dn_datablksz) {
zfs_panic_recover("zfs: accessing past end of object "
@@ -427,13 +431,14 @@ dmu_buf_hold_array_by_dnode(dnode_t *dn,
zio = zio_root(dn->dn_objset->os_spa, NULL, NULL, ZIO_FLAG_CANFAIL);
blkid = dbuf_whichblock(dn, 0, offset);
for (i = 0; i < nblks; i++) {
- dmu_buf_impl_t *db = dbuf_hold(dn, blkid+i, tag);
+ dmu_buf_impl_t *db = dbuf_hold(dn, blkid + i, tag);
if (db == NULL) {
rw_exit(&dn->dn_struct_rwlock);
dmu_buf_rele_array(dbp, nblks, tag);
zio_nowait(zio);
return (SET_ERROR(EIO));
}
+
/* initiate async i/o */
if (read)
(void) dbuf_read(db, zio, dbuf_flags);
@@ -443,6 +448,11 @@ dmu_buf_hold_array_by_dnode(dnode_t *dn,
#endif
dbp[i] = &db->db;
}
+
+ if ((flags & DMU_READ_NO_PREFETCH) == 0 && read &&
+ length < zfetch_array_rd_sz) {
+ dmu_zfetch(&dn->dn_zfetch, blkid, nblks);
+ }
rw_exit(&dn->dn_struct_rwlock);
/* wait for async i/o */
@@ -496,7 +506,8 @@ dmu_buf_hold_array(objset_t *os, uint64_
int
dmu_buf_hold_array_by_bonus(dmu_buf_t *db_fake, uint64_t offset,
- uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
+ uint64_t length, boolean_t read, void *tag, int *numbufsp,
+ dmu_buf_t ***dbpp)
{
dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
dnode_t *dn;
@@ -544,9 +555,6 @@ dmu_prefetch(objset_t *os, uint64_t obje
uint64_t blkid;
int nblks, err;
- if (zfs_prefetch_disable)
- return;
-
if (len == 0) { /* they're interested in the bonus buffer */
dn = DMU_META_DNODE(os);
Modified: stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c
==============================================================================
--- stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c
Sat Oct 3 11:27:23 2015 (r288593)
+++ stable/10/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c
Sat Oct 3 11:35:18 2015 (r288594)
@@ -24,7 +24,7 @@
*/
/*
- * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2013, 2014 by Delphix. All rights reserved.
*/
#include <sys/zfs_context.h>
@@ -36,19 +36,20 @@
#include <sys/kstat.h>
/*
- * I'm against tune-ables, but these should probably exist as tweakable globals
- * until we can get this working the way we want it to.
+ * This tunable disables predictive prefetch. Note that it leaves "prescient"
+ * prefetch (e.g. prefetch for zfs send) intact. Unlike predictive prefetch,
+ * prescient prefetch never issues i/os that end up not being needed,
+ * so it can't hurt performance.
*/
-
-int zfs_prefetch_disable = 0;
+boolean_t zfs_prefetch_disable = B_FALSE;
/* max # of streams per zfetch */
uint32_t zfetch_max_streams = 8;
/* min time before stream reclaim */
uint32_t zfetch_min_sec_reap = 2;
-/* max number of blocks to fetch at a time */
-uint32_t zfetch_block_cap = 256;
-/* number of bytes in a array_read at which we stop prefetching (1Mb) */
+/* max bytes to prefetch per stream (default 8MB) */
+uint32_t zfetch_max_distance = 8 * 1024 * 1024;
+/* number of bytes in a array_read at which we stop prefetching (1MB) */
uint64_t zfetch_array_rd_sz = 1024 * 1024;
SYSCTL_DECL(_vfs_zfs);
@@ -61,200 +62,34 @@ SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, m
TUNABLE_INT("vfs.zfs.zfetch.min_sec_reap", &zfetch_min_sec_reap);
SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, min_sec_reap, CTLFLAG_RWTUN,
&zfetch_min_sec_reap, 0, "Min time before stream reclaim");
-TUNABLE_INT("vfs.zfs.zfetch.block_cap", &zfetch_block_cap);
-SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, block_cap, CTLFLAG_RWTUN,
- &zfetch_block_cap, 0, "Max number of blocks to fetch at a time");
+TUNABLE_INT("vfs.zfs.zfetch.max_distance", &zfetch_max_distance);
+SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, max_distance, CTLFLAG_RWTUN,
+ &zfetch_max_distance, 0, "Max bytes to prefetch per stream");
TUNABLE_QUAD("vfs.zfs.zfetch.array_rd_sz", &zfetch_array_rd_sz);
SYSCTL_UQUAD(_vfs_zfs_zfetch, OID_AUTO, array_rd_sz, CTLFLAG_RWTUN,
&zfetch_array_rd_sz, 0,
"Number of bytes in a array_read at which we stop prefetching");
-/* forward decls for static routines */
-static boolean_t dmu_zfetch_colinear(zfetch_t *, zstream_t *);
-static void dmu_zfetch_dofetch(zfetch_t *, zstream_t *);
-static uint64_t dmu_zfetch_fetch(dnode_t *, uint64_t, uint64_t);
-static uint64_t dmu_zfetch_fetchsz(dnode_t *, uint64_t,
uint64_t);
-static boolean_t dmu_zfetch_find(zfetch_t *, zstream_t *, int);
-static int dmu_zfetch_stream_insert(zfetch_t *, zstream_t *);
-static zstream_t *dmu_zfetch_stream_reclaim(zfetch_t *);
-static void dmu_zfetch_stream_remove(zfetch_t *, zstream_t *);
-static int dmu_zfetch_streams_equal(zstream_t *, zstream_t *);
-
typedef struct zfetch_stats {
kstat_named_t zfetchstat_hits;
kstat_named_t zfetchstat_misses;
- kstat_named_t zfetchstat_colinear_hits;
- kstat_named_t zfetchstat_colinear_misses;
- kstat_named_t zfetchstat_stride_hits;
- kstat_named_t zfetchstat_stride_misses;
- kstat_named_t zfetchstat_reclaim_successes;
- kstat_named_t zfetchstat_reclaim_failures;
- kstat_named_t zfetchstat_stream_resets;
- kstat_named_t zfetchstat_stream_noresets;
- kstat_named_t zfetchstat_bogus_streams;
+ kstat_named_t zfetchstat_max_streams;
} zfetch_stats_t;
static zfetch_stats_t zfetch_stats = {
{ "hits", KSTAT_DATA_UINT64 },
{ "misses", KSTAT_DATA_UINT64 },
- { "colinear_hits", KSTAT_DATA_UINT64 },
- { "colinear_misses", KSTAT_DATA_UINT64 },
- { "stride_hits", KSTAT_DATA_UINT64 },
- { "stride_misses", KSTAT_DATA_UINT64 },
- { "reclaim_successes", KSTAT_DATA_UINT64 },
- { "reclaim_failures", KSTAT_DATA_UINT64 },
- { "streams_resets", KSTAT_DATA_UINT64 },
- { "streams_noresets", KSTAT_DATA_UINT64 },
- { "bogus_streams", KSTAT_DATA_UINT64 },
+ { "max_streams", KSTAT_DATA_UINT64 },
};
-#define ZFETCHSTAT_INCR(stat, val) \
- atomic_add_64(&zfetch_stats.stat.value.ui64, (val));
-
-#define ZFETCHSTAT_BUMP(stat) ZFETCHSTAT_INCR(stat, 1);
+#define ZFETCHSTAT_BUMP(stat) \
+ atomic_inc_64(&zfetch_stats.stat.value.ui64);
kstat_t *zfetch_ksp;
-/*
- * Given a zfetch structure and a zstream structure, determine whether the
- * blocks to be read are part of a co-linear pair of existing prefetch
- * streams. If a set is found, coalesce the streams, removing one, and
- * configure the prefetch so it looks for a strided access pattern.
- *
- * In other words: if we find two sequential access streams that are
- * the same length and distance N appart, and this read is N from the
- * last stream, then we are probably in a strided access pattern. So
- * combine the two sequential streams into a single strided stream.
- *
- * Returns whether co-linear streams were found.
- */
-static boolean_t
-dmu_zfetch_colinear(zfetch_t *zf, zstream_t *zh)
-{
- zstream_t *z_walk;
- zstream_t *z_comp;
-
- if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER))
- return (0);
-
- if (zh == NULL) {
- rw_exit(&zf->zf_rwlock);
- return (0);
- }
-
- for (z_walk = list_head(&zf->zf_stream); z_walk;
- z_walk = list_next(&zf->zf_stream, z_walk)) {
- for (z_comp = list_next(&zf->zf_stream, z_walk); z_comp;
- z_comp = list_next(&zf->zf_stream, z_comp)) {
- int64_t diff;
-
- if (z_walk->zst_len != z_walk->zst_stride ||
- z_comp->zst_len != z_comp->zst_stride) {
- continue;
- }
-
- diff = z_comp->zst_offset - z_walk->zst_offset;
- if (z_comp->zst_offset + diff == zh->zst_offset) {
- z_walk->zst_offset = zh->zst_offset;
- z_walk->zst_direction = diff < 0 ? -1 : 1;
- z_walk->zst_stride =
- diff * z_walk->zst_direction;
- z_walk->zst_ph_offset =
- zh->zst_offset + z_walk->zst_stride;
- dmu_zfetch_stream_remove(zf, z_comp);
- mutex_destroy(&z_comp->zst_lock);
- kmem_free(z_comp, sizeof (zstream_t));
-
- dmu_zfetch_dofetch(zf, z_walk);
-
- rw_exit(&zf->zf_rwlock);
- return (1);
- }
-
- diff = z_walk->zst_offset - z_comp->zst_offset;
- if (z_walk->zst_offset + diff == zh->zst_offset) {
- z_walk->zst_offset = zh->zst_offset;
- z_walk->zst_direction = diff < 0 ? -1 : 1;
- z_walk->zst_stride =
- diff * z_walk->zst_direction;
- z_walk->zst_ph_offset =
- zh->zst_offset + z_walk->zst_stride;
- dmu_zfetch_stream_remove(zf, z_comp);
- mutex_destroy(&z_comp->zst_lock);
- kmem_free(z_comp, sizeof (zstream_t));
-
- dmu_zfetch_dofetch(zf, z_walk);
-
- rw_exit(&zf->zf_rwlock);
- return (1);
- }
- }
- }
-
- rw_exit(&zf->zf_rwlock);
- return (0);
-}
-
-/*
- * Given a zstream_t, determine the bounds of the prefetch. Then call the
- * routine that actually prefetches the individual blocks.
- */
-static void
-dmu_zfetch_dofetch(zfetch_t *zf, zstream_t *zs)
-{
- uint64_t prefetch_tail;
- uint64_t prefetch_limit;
- uint64_t prefetch_ofst;
- uint64_t prefetch_len;
- uint64_t blocks_fetched;
-
- zs->zst_stride = MAX((int64_t)zs->zst_stride, zs->zst_len);
- zs->zst_cap = MIN(zfetch_block_cap, 2 * zs->zst_cap);
-
- prefetch_tail = MAX((int64_t)zs->zst_ph_offset,
- (int64_t)(zs->zst_offset + zs->zst_stride));
- /*
- * XXX: use a faster division method?
- */
- prefetch_limit = zs->zst_offset + zs->zst_len +
- (zs->zst_cap * zs->zst_stride) / zs->zst_len;
-
- while (prefetch_tail < prefetch_limit) {
- prefetch_ofst = zs->zst_offset + zs->zst_direction *
- (prefetch_tail - zs->zst_offset);
-
- prefetch_len = zs->zst_len;
-
- /*
- * Don't prefetch beyond the end of the file, if working
- * backwards.
- */
- if ((zs->zst_direction == ZFETCH_BACKWARD) &&
- (prefetch_ofst > prefetch_tail)) {
- prefetch_len += prefetch_ofst;
- prefetch_ofst = 0;
- }
-
- /* don't prefetch more than we're supposed to */
- if (prefetch_len > zs->zst_len)
- break;
-
- blocks_fetched = dmu_zfetch_fetch(zf->zf_dnode,
- prefetch_ofst, zs->zst_len);
-
- prefetch_tail += zs->zst_stride;
- /* stop if we've run out of stuff to prefetch */
- if (blocks_fetched < zs->zst_len)
- break;
- }
- zs->zst_ph_offset = prefetch_tail;
- zs->zst_last = ddi_get_lbolt();
-}
-
void
zfetch_init(void)
{
-
zfetch_ksp = kstat_create("zfs", 0, "zfetchstats", "misc",
KSTAT_TYPE_NAMED, sizeof (zfetch_stats) / sizeof (kstat_named_t),
KSTAT_FLAG_VIRTUAL);
@@ -282,285 +117,41 @@ zfetch_fini(void)
void
dmu_zfetch_init(zfetch_t *zf, dnode_t *dno)
{
- if (zf == NULL) {
+ if (zf == NULL)
return;
- }
zf->zf_dnode = dno;
- zf->zf_stream_cnt = 0;
- zf->zf_alloc_fail = 0;
list_create(&zf->zf_stream, sizeof (zstream_t),
- offsetof(zstream_t, zst_node));
+ offsetof(zstream_t, zs_node));
rw_init(&zf->zf_rwlock, NULL, RW_DEFAULT, NULL);
}
-/*
- * This function computes the actual size, in blocks, that can be prefetched,
- * and fetches it.
- */
-static uint64_t
-dmu_zfetch_fetch(dnode_t *dn, uint64_t blkid, uint64_t nblks)
-{
- uint64_t fetchsz;
- uint64_t i;
-
- fetchsz = dmu_zfetch_fetchsz(dn, blkid, nblks);
-
- for (i = 0; i < fetchsz; i++) {
- dbuf_prefetch(dn, 0, blkid + i, ZIO_PRIORITY_ASYNC_READ,
- ARC_FLAG_PREFETCH);
- }
-
- return (fetchsz);
-}
-
-/*
- * this function returns the number of blocks that would be prefetched, based
- * upon the supplied dnode, blockid, and nblks. This is used so that we can
- * update streams in place, and then prefetch with their old value after the
- * fact. This way, we can delay the prefetch, but subsequent accesses to the
- * stream won't result in the same data being prefetched multiple times.
- */
-static uint64_t
-dmu_zfetch_fetchsz(dnode_t *dn, uint64_t blkid, uint64_t nblks)
-{
- uint64_t fetchsz;
-
- if (blkid > dn->dn_maxblkid) {
- return (0);
- }
-
- /* compute fetch size */
- if (blkid + nblks + 1 > dn->dn_maxblkid) {
- fetchsz = (dn->dn_maxblkid - blkid) + 1;
- ASSERT(blkid + fetchsz - 1 <= dn->dn_maxblkid);
- } else {
- fetchsz = nblks;
- }
-
-
- return (fetchsz);
-}
-
-/*
- * given a zfetch and a zstream structure, see if there is an associated
zstream
- * for this block read. If so, it starts a prefetch for the stream it
- * located and returns true, otherwise it returns false
- */
-static boolean_t
-dmu_zfetch_find(zfetch_t *zf, zstream_t *zh, int prefetched)
+static void
+dmu_zfetch_stream_remove(zfetch_t *zf, zstream_t *zs)
{
- zstream_t *zs;
- int64_t diff;
- int reset = !prefetched;
- int rc = 0;
-
- if (zh == NULL)
- return (0);
-
- /*
- * XXX: This locking strategy is a bit coarse; however, it's impact has
- * yet to be tested. If this turns out to be an issue, it can be
- * modified in a number of different ways.
- */
-
- rw_enter(&zf->zf_rwlock, RW_READER);
-top:
-
- for (zs = list_head(&zf->zf_stream); zs;
- zs = list_next(&zf->zf_stream, zs)) {
-
- /*
- * XXX - should this be an assert?
- */
- if (zs->zst_len == 0) {
- /* bogus stream */
- ZFETCHSTAT_BUMP(zfetchstat_bogus_streams);
- continue;
- }
-
- /*
- * We hit this case when we are in a strided prefetch stream:
- * we will read "len" blocks before "striding".
- */
- if (zh->zst_offset >= zs->zst_offset &&
- zh->zst_offset < zs->zst_offset + zs->zst_len) {
- if (prefetched) {
- /* already fetched */
- ZFETCHSTAT_BUMP(zfetchstat_stride_hits);
- rc = 1;
- goto out;
- } else {
- ZFETCHSTAT_BUMP(zfetchstat_stride_misses);
- }
- }
-
- /*
- * This is the forward sequential read case: we increment
- * len by one each time we hit here, so we will enter this
- * case on every read.
- */
- if (zh->zst_offset == zs->zst_offset + zs->zst_len) {
-
- reset = !prefetched && zs->zst_len > 1;
-
- if (mutex_tryenter(&zs->zst_lock) == 0) {
- rc = 1;
- goto out;
- }
-
- if (zh->zst_offset != zs->zst_offset + zs->zst_len) {
- mutex_exit(&zs->zst_lock);
- goto top;
- }
- zs->zst_len += zh->zst_len;
- diff = zs->zst_len - zfetch_block_cap;
- if (diff > 0) {
- zs->zst_offset += diff;
- zs->zst_len = zs->zst_len > diff ?
- zs->zst_len - diff : 0;
- }
- zs->zst_direction = ZFETCH_FORWARD;
-
- break;
-
- /*
- * Same as above, but reading backwards through the file.
- */
- } else if (zh->zst_offset == zs->zst_offset - zh->zst_len) {
- /* backwards sequential access */
-
- reset = !prefetched && zs->zst_len > 1;
-
- if (mutex_tryenter(&zs->zst_lock) == 0) {
- rc = 1;
- goto out;
- }
-
- if (zh->zst_offset != zs->zst_offset - zh->zst_len) {
- mutex_exit(&zs->zst_lock);
- goto top;
- }
-
- zs->zst_offset = zs->zst_offset > zh->zst_len ?
- zs->zst_offset - zh->zst_len : 0;
- zs->zst_ph_offset = zs->zst_ph_offset > zh->zst_len ?
- zs->zst_ph_offset - zh->zst_len : 0;
- zs->zst_len += zh->zst_len;
-
- diff = zs->zst_len - zfetch_block_cap;
- if (diff > 0) {
- zs->zst_ph_offset = zs->zst_ph_offset > diff ?
- zs->zst_ph_offset - diff : 0;
- zs->zst_len = zs->zst_len > diff ?
- zs->zst_len - diff : zs->zst_len;
- }
- zs->zst_direction = ZFETCH_BACKWARD;
-
- break;
-
- } else if ((zh->zst_offset - zs->zst_offset - zs->zst_stride <
- zs->zst_len) && (zs->zst_len != zs->zst_stride)) {
- /* strided forward access */
-
- if (mutex_tryenter(&zs->zst_lock) == 0) {
- rc = 1;
- goto out;
- }
-
- if ((zh->zst_offset - zs->zst_offset - zs->zst_stride >=
- zs->zst_len) || (zs->zst_len == zs->zst_stride)) {
- mutex_exit(&zs->zst_lock);
- goto top;
- }
-
- zs->zst_offset += zs->zst_stride;
- zs->zst_direction = ZFETCH_FORWARD;
-
- break;
-
- } else if ((zh->zst_offset - zs->zst_offset + zs->zst_stride <
- zs->zst_len) && (zs->zst_len != zs->zst_stride)) {
- /* strided reverse access */
-
- if (mutex_tryenter(&zs->zst_lock) == 0) {
- rc = 1;
- goto out;
- }
-
- if ((zh->zst_offset - zs->zst_offset + zs->zst_stride >=
- zs->zst_len) || (zs->zst_len == zs->zst_stride)) {
- mutex_exit(&zs->zst_lock);
- goto top;
- }
-
- zs->zst_offset = zs->zst_offset > zs->zst_stride ?
- zs->zst_offset - zs->zst_stride : 0;
- zs->zst_ph_offset = (zs->zst_ph_offset >
- (2 * zs->zst_stride)) ?
- (zs->zst_ph_offset - (2 * zs->zst_stride)) : 0;
- zs->zst_direction = ZFETCH_BACKWARD;
-
- break;
- }
- }
-
- if (zs) {
- if (reset) {
- zstream_t *remove = zs;
-
- ZFETCHSTAT_BUMP(zfetchstat_stream_resets);
- rc = 0;
- mutex_exit(&zs->zst_lock);
- rw_exit(&zf->zf_rwlock);
- rw_enter(&zf->zf_rwlock, RW_WRITER);
- /*
- * Relocate the stream, in case someone removes
- * it while we were acquiring the WRITER lock.
- */
- for (zs = list_head(&zf->zf_stream); zs;
- zs = list_next(&zf->zf_stream, zs)) {
- if (zs == remove) {
- dmu_zfetch_stream_remove(zf, zs);
- mutex_destroy(&zs->zst_lock);
- kmem_free(zs, sizeof (zstream_t));
- break;
- }
- }
- } else {
- ZFETCHSTAT_BUMP(zfetchstat_stream_noresets);
- rc = 1;
- dmu_zfetch_dofetch(zf, zs);
- mutex_exit(&zs->zst_lock);
- }
- }
-out:
- rw_exit(&zf->zf_rwlock);
- return (rc);
+ ASSERT(RW_WRITE_HELD(&zf->zf_rwlock));
+ list_remove(&zf->zf_stream, zs);
+ mutex_destroy(&zs->zs_lock);
+ kmem_free(zs, sizeof (*zs));
}
/*
- * Clean-up state associated with a zfetch structure. This frees allocated
- * structure members, empties the zf_stream tree, and generally makes things
- * nice. This doesn't free the zfetch_t itself, that's left to the caller.
+ * Clean-up state associated with a zfetch structure (e.g. destroy the
+ * streams). This doesn't free the zfetch_t itself, that's left to the caller.
*/
void
-dmu_zfetch_rele(zfetch_t *zf)
+dmu_zfetch_fini(zfetch_t *zf)
{
- zstream_t *zs;
- zstream_t *zs_next;
+ zstream_t *zs;
ASSERT(!RW_LOCK_HELD(&zf->zf_rwlock));
- for (zs = list_head(&zf->zf_stream); zs; zs = zs_next) {
- zs_next = list_next(&zf->zf_stream, zs);
-
- list_remove(&zf->zf_stream, zs);
- mutex_destroy(&zs->zst_lock);
- kmem_free(zs, sizeof (zstream_t));
- }
+ rw_enter(&zf->zf_rwlock, RW_WRITER);
+ while ((zs = list_head(&zf->zf_stream)) != NULL)
+ dmu_zfetch_stream_remove(zf, zs);
+ rw_exit(&zf->zf_rwlock);
list_destroy(&zf->zf_stream);
rw_destroy(&zf->zf_rwlock);
@@ -568,103 +159,55 @@ dmu_zfetch_rele(zfetch_t *zf)
}
/*
- * Given a zfetch and zstream structure, insert the zstream structure into the
- * AVL tree contained within the zfetch structure. Peform the appropriate
- * book-keeping. It is possible that another thread has inserted a stream
which
- * matches one that we are about to insert, so we must be sure to check for
this
- * case. If one is found, return failure, and let the caller cleanup the
- * duplicates.
+ * If there aren't too many streams already, create a new stream.
+ * The "blkid" argument is the next block that we expect this stream to access.
+ * While we're here, clean up old streams (which haven't been
+ * accessed for at least zfetch_min_sec_reap seconds).
*/
-static int
-dmu_zfetch_stream_insert(zfetch_t *zf, zstream_t *zs)
+static void
+dmu_zfetch_stream_create(zfetch_t *zf, uint64_t blkid)
{
- zstream_t *zs_walk;
- zstream_t *zs_next;
+ zstream_t *zs_next;
+ int numstreams = 0;
ASSERT(RW_WRITE_HELD(&zf->zf_rwlock));
- for (zs_walk = list_head(&zf->zf_stream); zs_walk; zs_walk = zs_next) {
- zs_next = list_next(&zf->zf_stream, zs_walk);
-
- if (dmu_zfetch_streams_equal(zs_walk, zs)) {
- return (0);
- }
- }
-
- list_insert_head(&zf->zf_stream, zs);
- zf->zf_stream_cnt++;
- return (1);
-}
-
-
-/*
- * Walk the list of zstreams in the given zfetch, find an old one (by time),
and
- * reclaim it for use by the caller.
- */
-static zstream_t *
-dmu_zfetch_stream_reclaim(zfetch_t *zf)
-{
- zstream_t *zs;
- clock_t ticks;
-
- ticks = zfetch_min_sec_reap * hz;
- if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER))
- return (0);
-
- for (zs = list_head(&zf->zf_stream); zs;
- zs = list_next(&zf->zf_stream, zs)) {
-
- if (ddi_get_lbolt() - zs->zst_last > ticks)
- break;
+ /*
+ * Clean up old streams.
+ */
+ for (zstream_t *zs = list_head(&zf->zf_stream);
+ zs != NULL; zs = zs_next) {
+ zs_next = list_next(&zf->zf_stream, zs);
+ if (((gethrtime() - zs->zs_atime) / NANOSEC) >
+ zfetch_min_sec_reap)
+ dmu_zfetch_stream_remove(zf, zs);
+ else
+ numstreams++;
}
- if (zs) {
- dmu_zfetch_stream_remove(zf, zs);
- mutex_destroy(&zs->zst_lock);
- bzero(zs, sizeof (zstream_t));
- } else {
- zf->zf_alloc_fail++;
+ /*
+ * The maximum number of streams is normally zfetch_max_streams,
+ * but for small files we lower it such that it's at least possible
+ * for all the streams to be non-overlapping.
+ *
+ * If we are already at the maximum number of streams for this file,
+ * even after removing old streams, then don't create this stream.
+ */
+ uint32_t max_streams = MAX(1, MIN(zfetch_max_streams,
+ zf->zf_dnode->dn_maxblkid * zf->zf_dnode->dn_datablksz /
+ zfetch_max_distance));
+ if (numstreams >= max_streams) {
+ ZFETCHSTAT_BUMP(zfetchstat_max_streams);
+ return;
}
- rw_exit(&zf->zf_rwlock);
-
- return (zs);
-}
-
-/*
- * Given a zfetch and zstream structure, remove the zstream structure from its
- * container in the zfetch structure. Perform the appropriate book-keeping.
- */
-static void
-dmu_zfetch_stream_remove(zfetch_t *zf, zstream_t *zs)
-{
- ASSERT(RW_WRITE_HELD(&zf->zf_rwlock));
-
- list_remove(&zf->zf_stream, zs);
- zf->zf_stream_cnt--;
-}
-
-static int
-dmu_zfetch_streams_equal(zstream_t *zs1, zstream_t *zs2)
-{
- if (zs1->zst_offset != zs2->zst_offset)
- return (0);
-
- if (zs1->zst_len != zs2->zst_len)
- return (0);
- if (zs1->zst_stride != zs2->zst_stride)
- return (0);
+ zstream_t *zs = kmem_zalloc(sizeof (*zs), KM_SLEEP);
+ zs->zs_blkid = blkid;
+ zs->zs_pf_blkid = blkid;
*** DIFF OUTPUT TRUNCATED AT 1000 LINES ***
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