Date: Sat, 12 Sep 2015 08:35:52 +0000 (UTC) From: Xin LI <delphij@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r287702 - in head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys Message-ID: <201509120835.t8C8Zqpw036732@repo.freebsd.org>
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Author: delphij Date: Sat Sep 12 08:35:51 2015 New Revision: 287702 URL: https://svnweb.freebsd.org/changeset/base/287702 Log: MFV r287624: 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 The sysctl variable/loader tunable vfs.zfs.zfetch.block_cap have been replaced by vfs.zfs.zfetch.max_distance, which controls maximum bytes to prefetch per stream.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: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dnode.c head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/arc.h head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/dmu.h head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/dmu_zfetch.h Directory Properties: head/sys/cddl/contrib/opensolaris/ (props changed) Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c ============================================================================== --- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c Sat Sep 12 08:24:25 2015 (r287701) +++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c Sat Sep 12 08:35:51 2015 (r287702) @@ -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. @@ -582,6 +582,8 @@ 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 = { @@ -680,7 +682,9 @@ 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) @@ -4250,6 +4254,36 @@ 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); @@ -4258,7 +4292,7 @@ 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); @@ -4283,6 +4317,19 @@ 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 @@ -4345,12 +4392,16 @@ 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) @@ -4373,11 +4424,13 @@ 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) @@ -4395,6 +4448,8 @@ 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); @@ -4437,6 +4492,11 @@ 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: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c ============================================================================== --- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Sat Sep 12 08:24:25 2015 (r287701) +++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Sat Sep 12 08:35:51 2015 (r287702) @@ -618,7 +618,7 @@ 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; @@ -664,7 +664,6 @@ 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; } @@ -687,10 +686,8 @@ 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 @@ -723,8 +720,7 @@ 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); @@ -733,13 +729,12 @@ 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); @@ -758,8 +753,7 @@ 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); @@ -2059,6 +2053,9 @@ 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: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c ============================================================================== --- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c Sat Sep 12 08:24:25 2015 (r287701) +++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu.c Sat Sep 12 08:35:51 2015 (r287702) @@ -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. */ @@ -389,7 +389,7 @@ 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; @@ -399,15 +399,19 @@ 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 " @@ -426,13 +430,14 @@ 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); @@ -442,6 +447,11 @@ 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 */ @@ -495,7 +505,8 @@ 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; @@ -543,9 +554,6 @@ 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: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c ============================================================================== --- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c Sat Sep 12 08:24:25 2015 (r287701) +++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c Sat Sep 12 08:35:51 2015 (r287702) @@ -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); @@ -59,198 +60,32 @@ SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, m &zfetch_max_streams, 0, "Max # of streams per zfetch"); SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, min_sec_reap, CTLFLAG_RWTUN, &zfetch_min_sec_reap, 0, "Min time before stream reclaim"); -SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, block_cap, CTLFLAG_RWTUN, - &zfetch_block_cap, 0, "Max number of blocks to fetch at a time"); +SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, max_distance, CTLFLAG_RWTUN, + &zfetch_max_distance, 0, "Max bytes to prefetch per stream"); 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); @@ -278,285 +113,41 @@ 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); @@ -564,103 +155,55 @@ 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; + zs->zs_atime = gethrtime(); + mutex_init(&zs->zs_lock, NULL, MUTEX_DEFAULT, NULL); *** DIFF OUTPUT TRUNCATED AT 1000 LINES ***
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