Fix perfomance problem with ZFS prefetch caching [1]
Add statistics for ZFS prefetch (sysctl kstat.zfs.misc.zfetchstats) Partial import of OpenSolaris onnv revision 10474:0e96dd3b905a Reported by: jhell@dataix.net (private e-mail) [1] Approved by: pjd, delphij (mentor) Obtained from: OpenSolaris (Bug ID 6859997, 6868951) MFC after: 3 days
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@ -1192,6 +1192,7 @@ dmu_init(void)
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{
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dbuf_init();
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dnode_init();
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zfetch_init();
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arc_init();
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l2arc_init();
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}
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@ -1200,6 +1201,7 @@ void
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dmu_fini(void)
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{
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arc_fini();
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zfetch_fini();
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dnode_fini();
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dbuf_fini();
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l2arc_fini();
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@ -19,18 +19,17 @@
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* CDDL HEADER END
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*/
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/*
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* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
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* Copyright 2009 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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#pragma ident "%Z%%M% %I% %E% SMI"
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#include <sys/zfs_context.h>
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#include <sys/dnode.h>
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#include <sys/dmu_objset.h>
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#include <sys/dmu_zfetch.h>
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#include <sys/dmu.h>
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#include <sys/dbuf.h>
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#include <sys/kstat.h>
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/*
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* I'm against tune-ables, but these should probably exist as tweakable globals
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@ -77,6 +76,41 @@ static zstream_t *dmu_zfetch_stream_reclaim(zfetch_t *);
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static void dmu_zfetch_stream_remove(zfetch_t *, zstream_t *);
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static int dmu_zfetch_streams_equal(zstream_t *, zstream_t *);
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typedef struct zfetch_stats {
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kstat_named_t zfetchstat_hits;
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kstat_named_t zfetchstat_misses;
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kstat_named_t zfetchstat_colinear_hits;
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kstat_named_t zfetchstat_colinear_misses;
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kstat_named_t zfetchstat_stride_hits;
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kstat_named_t zfetchstat_stride_misses;
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kstat_named_t zfetchstat_reclaim_successes;
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kstat_named_t zfetchstat_reclaim_failures;
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kstat_named_t zfetchstat_stream_resets;
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kstat_named_t zfetchstat_stream_noresets;
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kstat_named_t zfetchstat_bogus_streams;
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} zfetch_stats_t;
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static zfetch_stats_t zfetch_stats = {
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{ "hits", KSTAT_DATA_UINT64 },
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{ "misses", KSTAT_DATA_UINT64 },
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{ "colinear_hits", KSTAT_DATA_UINT64 },
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{ "colinear_misses", KSTAT_DATA_UINT64 },
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{ "stride_hits", KSTAT_DATA_UINT64 },
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{ "stride_misses", KSTAT_DATA_UINT64 },
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{ "reclaim_successes", KSTAT_DATA_UINT64 },
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{ "reclaim_failures", KSTAT_DATA_UINT64 },
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{ "streams_resets", KSTAT_DATA_UINT64 },
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{ "streams_noresets", KSTAT_DATA_UINT64 },
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{ "bogus_streams", KSTAT_DATA_UINT64 },
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};
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#define ZFETCHSTAT_INCR(stat, val) \
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atomic_add_64(&zfetch_stats.stat.value.ui64, (val));
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#define ZFETCHSTAT_BUMP(stat) ZFETCHSTAT_INCR(stat, 1);
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kstat_t *zfetch_ksp;
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/*
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* Given a zfetch structure and a zstream structure, determine whether the
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* blocks to be read are part of a co-linear pair of existing prefetch
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@ -213,6 +247,29 @@ dmu_zfetch_dofetch(zfetch_t *zf, zstream_t *zs)
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zs->zst_last = LBOLT;
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}
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void
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zfetch_init(void)
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{
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zfetch_ksp = kstat_create("zfs", 0, "zfetchstats", "misc",
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KSTAT_TYPE_NAMED, sizeof (zfetch_stats) / sizeof (kstat_named_t),
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KSTAT_FLAG_VIRTUAL);
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if (zfetch_ksp != NULL) {
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zfetch_ksp->ks_data = &zfetch_stats;
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kstat_install(zfetch_ksp);
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}
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}
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void
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zfetch_fini(void)
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{
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if (zfetch_ksp != NULL) {
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kstat_delete(zfetch_ksp);
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zfetch_ksp = NULL;
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}
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}
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/*
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* This takes a pointer to a zfetch structure and a dnode. It performs the
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* necessary setup for the zfetch structure, grokking data from the
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@ -283,7 +340,7 @@ dmu_zfetch_fetchsz(dnode_t *dn, uint64_t blkid, uint64_t nblks)
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}
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/*
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* given a zfetch and a zsearch structure, see if there is an associated zstream
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* given a zfetch and a zstream structure, see if there is an associated zstream
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* for this block read. If so, it starts a prefetch for the stream it
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* located and returns true, otherwise it returns false
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*/
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@ -315,6 +372,7 @@ dmu_zfetch_find(zfetch_t *zf, zstream_t *zh, int prefetched)
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*/
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if (zs->zst_len == 0) {
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/* bogus stream */
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ZFETCHSTAT_BUMP(zfetchstat_bogus_streams);
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continue;
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}
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@ -324,9 +382,14 @@ dmu_zfetch_find(zfetch_t *zf, zstream_t *zh, int prefetched)
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*/
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if (zh->zst_offset >= zs->zst_offset &&
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zh->zst_offset < zs->zst_offset + zs->zst_len) {
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/* already fetched */
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rc = 1;
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goto out;
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if (prefetched) {
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/* already fetched */
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ZFETCHSTAT_BUMP(zfetchstat_stride_hits);
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rc = 1;
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goto out;
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} else {
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ZFETCHSTAT_BUMP(zfetchstat_stride_misses);
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}
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}
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/*
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@ -439,6 +502,7 @@ dmu_zfetch_find(zfetch_t *zf, zstream_t *zh, int prefetched)
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if (reset) {
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zstream_t *remove = zs;
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ZFETCHSTAT_BUMP(zfetchstat_stream_resets);
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rc = 0;
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mutex_exit(&zs->zst_lock);
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rw_exit(&zf->zf_rwlock);
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@ -457,6 +521,7 @@ dmu_zfetch_find(zfetch_t *zf, zstream_t *zh, int prefetched)
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}
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}
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} else {
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ZFETCHSTAT_BUMP(zfetchstat_stream_noresets);
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rc = 1;
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dmu_zfetch_dofetch(zf, zs);
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mutex_exit(&zs->zst_lock);
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@ -513,13 +578,12 @@ dmu_zfetch_stream_insert(zfetch_t *zf, zstream_t *zs)
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zs_next = list_next(&zf->zf_stream, zs_walk);
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if (dmu_zfetch_streams_equal(zs_walk, zs)) {
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return (0);
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return (0);
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}
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}
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list_insert_head(&zf->zf_stream, zs);
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zf->zf_stream_cnt++;
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return (1);
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}
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@ -623,8 +687,15 @@ dmu_zfetch(zfetch_t *zf, uint64_t offset, uint64_t size, int prefetched)
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P2ALIGN(offset, blksz)) >> blkshft;
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fetched = dmu_zfetch_find(zf, &zst, prefetched);
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if (!fetched) {
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fetched = dmu_zfetch_colinear(zf, &zst);
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if (fetched) {
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ZFETCHSTAT_BUMP(zfetchstat_hits);
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} else {
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ZFETCHSTAT_BUMP(zfetchstat_misses);
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if (fetched = dmu_zfetch_colinear(zf, &zst)) {
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ZFETCHSTAT_BUMP(zfetchstat_colinear_hits);
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} else {
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ZFETCHSTAT_BUMP(zfetchstat_colinear_misses);
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}
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}
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if (!fetched) {
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@ -634,11 +705,14 @@ dmu_zfetch(zfetch_t *zf, uint64_t offset, uint64_t size, int prefetched)
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* we still couldn't find a stream, drop the lock, and allocate
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* one if possible. Otherwise, give up and go home.
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*/
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if (newstream == NULL) {
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if (newstream) {
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ZFETCHSTAT_BUMP(zfetchstat_reclaim_successes);
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} else {
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uint64_t maxblocks;
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uint32_t max_streams;
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uint32_t cur_streams;
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ZFETCHSTAT_BUMP(zfetchstat_reclaim_failures);
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cur_streams = zf->zf_stream_cnt;
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maxblocks = zf->zf_dnode->dn_maxblkid;
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@ -651,7 +725,6 @@ dmu_zfetch(zfetch_t *zf, uint64_t offset, uint64_t size, int prefetched)
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if (cur_streams >= max_streams) {
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return;
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}
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newstream = kmem_zalloc(sizeof (zstream_t), KM_SLEEP);
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}
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@ -19,15 +19,13 @@
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* CDDL HEADER END
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*/
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/*
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* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
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* Copyright 2009 Sun Microsystems, Inc. All rights reserved.
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* Use is subject to license terms.
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*/
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#ifndef _DFETCH_H
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#define _DFETCH_H
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#pragma ident "%Z%%M% %I% %E% SMI"
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#include <sys/zfs_context.h>
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#ifdef __cplusplus
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@ -63,6 +61,9 @@ typedef struct zfetch {
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uint64_t zf_alloc_fail; /* # of failed attempts to alloc strm */
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} zfetch_t;
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void zfetch_init(void);
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void zfetch_fini(void);
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void dmu_zfetch_init(zfetch_t *, struct dnode *);
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void dmu_zfetch_rele(zfetch_t *);
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void dmu_zfetch(zfetch_t *, uint64_t, uint64_t, int);
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