diff --git a/module/zfs/dmu_zfetch.c b/module/zfs/dmu_zfetch.c index 915d99916d2e..ed50f1889b59 100644 --- a/module/zfs/dmu_zfetch.c +++ b/module/zfs/dmu_zfetch.c @@ -1,773 +1,773 @@ /* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or https://opensource.org/licenses/CDDL-1.0. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright 2009 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ /* * Copyright (c) 2013, 2017 by Delphix. All rights reserved. */ #include #include #include #include #include #include #include #include #include /* * 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. */ static int zfs_prefetch_disable = B_FALSE; /* max # of streams per zfetch */ static unsigned int zfetch_max_streams = 8; /* min time before stream reclaim */ static unsigned int zfetch_min_sec_reap = 1; /* max time before stream delete */ static unsigned int zfetch_max_sec_reap = 2; #ifdef _ILP32 /* min bytes to prefetch per stream (default 2MB) */ static unsigned int zfetch_min_distance = 2 * 1024 * 1024; /* max bytes to prefetch per stream (default 8MB) */ unsigned int zfetch_max_distance = 8 * 1024 * 1024; #else /* min bytes to prefetch per stream (default 4MB) */ static unsigned int zfetch_min_distance = 4 * 1024 * 1024; /* max bytes to prefetch per stream (default 64MB) */ unsigned int zfetch_max_distance = 64 * 1024 * 1024; #endif /* max bytes to prefetch indirects for per stream (default 64MB) */ unsigned int zfetch_max_idistance = 64 * 1024 * 1024; /* max request reorder distance within a stream (default 16MB) */ unsigned int zfetch_max_reorder = 16 * 1024 * 1024; /* Max log2 fraction of holes in a stream */ unsigned int zfetch_hole_shift = 2; typedef struct zfetch_stats { kstat_named_t zfetchstat_hits; kstat_named_t zfetchstat_future; kstat_named_t zfetchstat_stride; kstat_named_t zfetchstat_past; kstat_named_t zfetchstat_misses; kstat_named_t zfetchstat_max_streams; kstat_named_t zfetchstat_io_issued; kstat_named_t zfetchstat_io_active; } zfetch_stats_t; static zfetch_stats_t zfetch_stats = { { "hits", KSTAT_DATA_UINT64 }, { "future", KSTAT_DATA_UINT64 }, { "stride", KSTAT_DATA_UINT64 }, { "past", KSTAT_DATA_UINT64 }, { "misses", KSTAT_DATA_UINT64 }, { "max_streams", KSTAT_DATA_UINT64 }, { "io_issued", KSTAT_DATA_UINT64 }, { "io_active", KSTAT_DATA_UINT64 }, }; struct { wmsum_t zfetchstat_hits; wmsum_t zfetchstat_future; wmsum_t zfetchstat_stride; wmsum_t zfetchstat_past; wmsum_t zfetchstat_misses; wmsum_t zfetchstat_max_streams; wmsum_t zfetchstat_io_issued; aggsum_t zfetchstat_io_active; } zfetch_sums; #define ZFETCHSTAT_BUMP(stat) \ wmsum_add(&zfetch_sums.stat, 1) #define ZFETCHSTAT_ADD(stat, val) \ wmsum_add(&zfetch_sums.stat, val) static kstat_t *zfetch_ksp; static int zfetch_kstats_update(kstat_t *ksp, int rw) { zfetch_stats_t *zs = ksp->ks_data; if (rw == KSTAT_WRITE) return (EACCES); zs->zfetchstat_hits.value.ui64 = wmsum_value(&zfetch_sums.zfetchstat_hits); zs->zfetchstat_future.value.ui64 = wmsum_value(&zfetch_sums.zfetchstat_future); zs->zfetchstat_stride.value.ui64 = wmsum_value(&zfetch_sums.zfetchstat_stride); zs->zfetchstat_past.value.ui64 = wmsum_value(&zfetch_sums.zfetchstat_past); zs->zfetchstat_misses.value.ui64 = wmsum_value(&zfetch_sums.zfetchstat_misses); zs->zfetchstat_max_streams.value.ui64 = wmsum_value(&zfetch_sums.zfetchstat_max_streams); zs->zfetchstat_io_issued.value.ui64 = wmsum_value(&zfetch_sums.zfetchstat_io_issued); zs->zfetchstat_io_active.value.ui64 = aggsum_value(&zfetch_sums.zfetchstat_io_active); return (0); } void zfetch_init(void) { wmsum_init(&zfetch_sums.zfetchstat_hits, 0); wmsum_init(&zfetch_sums.zfetchstat_future, 0); wmsum_init(&zfetch_sums.zfetchstat_stride, 0); wmsum_init(&zfetch_sums.zfetchstat_past, 0); wmsum_init(&zfetch_sums.zfetchstat_misses, 0); wmsum_init(&zfetch_sums.zfetchstat_max_streams, 0); wmsum_init(&zfetch_sums.zfetchstat_io_issued, 0); aggsum_init(&zfetch_sums.zfetchstat_io_active, 0); zfetch_ksp = kstat_create("zfs", 0, "zfetchstats", "misc", KSTAT_TYPE_NAMED, sizeof (zfetch_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL); if (zfetch_ksp != NULL) { zfetch_ksp->ks_data = &zfetch_stats; zfetch_ksp->ks_update = zfetch_kstats_update; kstat_install(zfetch_ksp); } } void zfetch_fini(void) { if (zfetch_ksp != NULL) { kstat_delete(zfetch_ksp); zfetch_ksp = NULL; } wmsum_fini(&zfetch_sums.zfetchstat_hits); wmsum_fini(&zfetch_sums.zfetchstat_future); wmsum_fini(&zfetch_sums.zfetchstat_stride); wmsum_fini(&zfetch_sums.zfetchstat_past); wmsum_fini(&zfetch_sums.zfetchstat_misses); wmsum_fini(&zfetch_sums.zfetchstat_max_streams); wmsum_fini(&zfetch_sums.zfetchstat_io_issued); ASSERT0(aggsum_value(&zfetch_sums.zfetchstat_io_active)); aggsum_fini(&zfetch_sums.zfetchstat_io_active); } /* * This takes a pointer to a zfetch structure and a dnode. It performs the * necessary setup for the zfetch structure, grokking data from the * associated dnode. */ void dmu_zfetch_init(zfetch_t *zf, dnode_t *dno) { if (zf == NULL) return; zf->zf_dnode = dno; zf->zf_numstreams = 0; list_create(&zf->zf_stream, sizeof (zstream_t), offsetof(zstream_t, zs_node)); mutex_init(&zf->zf_lock, NULL, MUTEX_DEFAULT, NULL); } static void dmu_zfetch_stream_fini(zstream_t *zs) { ASSERT(!list_link_active(&zs->zs_node)); zfs_refcount_destroy(&zs->zs_callers); zfs_refcount_destroy(&zs->zs_refs); kmem_free(zs, sizeof (*zs)); } static void dmu_zfetch_stream_remove(zfetch_t *zf, zstream_t *zs) { ASSERT(MUTEX_HELD(&zf->zf_lock)); list_remove(&zf->zf_stream, zs); zf->zf_numstreams--; membar_producer(); if (zfs_refcount_remove(&zs->zs_refs, NULL) == 0) dmu_zfetch_stream_fini(zs); } /* * 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_fini(zfetch_t *zf) { zstream_t *zs; mutex_enter(&zf->zf_lock); while ((zs = list_head(&zf->zf_stream)) != NULL) dmu_zfetch_stream_remove(zf, zs); mutex_exit(&zf->zf_lock); list_destroy(&zf->zf_stream); mutex_destroy(&zf->zf_lock); zf->zf_dnode = NULL; } /* * If there aren't too many active streams already, create one more. * In process delete/reuse all streams without hits for zfetch_max_sec_reap. * If needed, reuse oldest stream without hits for zfetch_min_sec_reap or ever. * The "blkid" argument is the next block that we expect this stream to access. */ static void dmu_zfetch_stream_create(zfetch_t *zf, uint64_t blkid) { zstream_t *zs, *zs_next, *zs_old = NULL; uint_t now = gethrestime_sec(), t; ASSERT(MUTEX_HELD(&zf->zf_lock)); /* * Delete too old streams, reusing the first found one. */ t = now - zfetch_max_sec_reap; for (zs = list_head(&zf->zf_stream); zs != NULL; zs = zs_next) { zs_next = list_next(&zf->zf_stream, zs); /* * Skip if still active. 1 -- zf_stream reference. */ if ((int)(zs->zs_atime - t) >= 0) continue; if (zfs_refcount_count(&zs->zs_refs) != 1) continue; if (zs_old) dmu_zfetch_stream_remove(zf, zs); else zs_old = zs; } if (zs_old) { zs = zs_old; list_remove(&zf->zf_stream, zs); goto reuse; } /* * 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. */ uint32_t max_streams = MAX(1, MIN(zfetch_max_streams, (zf->zf_dnode->dn_maxblkid << zf->zf_dnode->dn_datablkshift) / zfetch_max_distance)); if (zf->zf_numstreams >= max_streams) { t = now - zfetch_min_sec_reap; for (zs = list_head(&zf->zf_stream); zs != NULL; zs = list_next(&zf->zf_stream, zs)) { if ((int)(zs->zs_atime - t) >= 0) continue; if (zfs_refcount_count(&zs->zs_refs) != 1) continue; if (zs_old == NULL || (int)(zs_old->zs_atime - zs->zs_atime) >= 0) zs_old = zs; } if (zs_old) { zs = zs_old; list_remove(&zf->zf_stream, zs); goto reuse; } ZFETCHSTAT_BUMP(zfetchstat_max_streams); return; } zs = kmem_zalloc(sizeof (*zs), KM_SLEEP); zfs_refcount_create(&zs->zs_callers); zfs_refcount_create(&zs->zs_refs); /* One reference for zf_stream. */ zfs_refcount_add(&zs->zs_refs, NULL); zf->zf_numstreams++; reuse: list_insert_head(&zf->zf_stream, zs); zs->zs_blkid = blkid; /* Allow immediate stream reuse until first hit. */ zs->zs_atime = now - zfetch_min_sec_reap; memset(zs->zs_ranges, 0, sizeof (zs->zs_ranges)); zs->zs_pf_dist = 0; zs->zs_ipf_dist = 0; zs->zs_pf_start = blkid; zs->zs_pf_end = blkid; zs->zs_ipf_start = blkid; zs->zs_ipf_end = blkid; zs->zs_missed = B_FALSE; zs->zs_more = B_FALSE; } static void dmu_zfetch_done(void *arg, uint64_t level, uint64_t blkid, boolean_t io_issued) { zstream_t *zs = arg; if (io_issued && level == 0 && blkid < zs->zs_blkid) zs->zs_more = B_TRUE; if (zfs_refcount_remove(&zs->zs_refs, NULL) == 0) dmu_zfetch_stream_fini(zs); aggsum_add(&zfetch_sums.zfetchstat_io_active, -1); } /* * Process stream hit access for nblks blocks starting at zs_blkid. Return * number of blocks to proceed for after aggregation with future ranges. */ static uint64_t dmu_zfetch_hit(zstream_t *zs, uint64_t nblks) { uint_t i, j; /* Optimize sequential accesses (no future ranges). */ if (zs->zs_ranges[0].start == 0) goto done; /* Look for intersections with further ranges. */ for (i = 0; i < ZFETCH_RANGES; i++) { zsrange_t *r = &zs->zs_ranges[i]; if (r->start == 0 || r->start > nblks) break; if (r->end >= nblks) { nblks = r->end; i++; break; } } /* Delete all found intersecting ranges, updates remaining. */ for (j = 0; i < ZFETCH_RANGES; i++, j++) { if (zs->zs_ranges[i].start == 0) break; ASSERT3U(zs->zs_ranges[i].start, >, nblks); ASSERT3U(zs->zs_ranges[i].end, >, nblks); zs->zs_ranges[j].start = zs->zs_ranges[i].start - nblks; zs->zs_ranges[j].end = zs->zs_ranges[i].end - nblks; } if (j < ZFETCH_RANGES) { zs->zs_ranges[j].start = 0; zs->zs_ranges[j].end = 0; } done: zs->zs_blkid += nblks; return (nblks); } /* * Process future stream access for nblks blocks starting at blkid. Return * number of blocks to proceed for if future ranges reach fill threshold. */ static uint64_t dmu_zfetch_future(zstream_t *zs, uint64_t blkid, uint64_t nblks) { ASSERT3U(blkid, >, zs->zs_blkid); blkid -= zs->zs_blkid; ASSERT3U(blkid + nblks, <=, UINT16_MAX); /* Search for first and last intersection or insert point. */ uint_t f = ZFETCH_RANGES, l = 0, i; for (i = 0; i < ZFETCH_RANGES; i++) { zsrange_t *r = &zs->zs_ranges[i]; if (r->start == 0 || r->start > blkid + nblks) break; if (r->end < blkid) continue; if (f > i) f = i; if (l < i) l = i; } if (f <= l) { /* Got some intersecting range, expand it if needed. */ if (zs->zs_ranges[f].start > blkid) zs->zs_ranges[f].start = blkid; zs->zs_ranges[f].end = MAX(zs->zs_ranges[l].end, blkid + nblks); if (f < l) { /* Got more than one intersection, remove others. */ for (f++, l++; l < ZFETCH_RANGES; f++, l++) { zs->zs_ranges[f].start = zs->zs_ranges[l].start; zs->zs_ranges[f].end = zs->zs_ranges[l].end; } - zs->zs_ranges[ZFETCH_RANGES - 1].start = 0; - zs->zs_ranges[ZFETCH_RANGES - 1].end = 0; + zs->zs_ranges[f].start = 0; + zs->zs_ranges[f].end = 0; } } else if (i < ZFETCH_RANGES) { /* Got no intersecting ranges, insert new one. */ for (l = ZFETCH_RANGES - 1; l > i; l--) { zs->zs_ranges[l].start = zs->zs_ranges[l - 1].start; zs->zs_ranges[l].end = zs->zs_ranges[l - 1].end; } zs->zs_ranges[i].start = blkid; zs->zs_ranges[i].end = blkid + nblks; } else { /* No space left to insert. Drop the range. */ return (0); } /* Check if with the new access addition we reached fill threshold. */ if (zfetch_hole_shift >= 16) return (0); uint_t hole = 0; for (i = f = l = 0; i < ZFETCH_RANGES; i++) { zsrange_t *r = &zs->zs_ranges[i]; if (r->start == 0) break; hole += r->start - f; f = r->end; if (hole <= r->end >> zfetch_hole_shift) l = r->end; } if (l > 0) return (dmu_zfetch_hit(zs, l)); return (0); } /* * This is the predictive prefetch entry point. dmu_zfetch_prepare() * associates dnode access specified with blkid and nblks arguments with * prefetch stream, predicts further accesses based on that stats and returns * the stream pointer on success. That pointer must later be passed to * dmu_zfetch_run() to initiate the speculative prefetch for the stream and * release it. dmu_zfetch() is a wrapper for simple cases when window between * prediction and prefetch initiation is not needed. * fetch_data argument specifies whether actual data blocks should be fetched: * FALSE -- prefetch only indirect blocks for predicted data blocks; * TRUE -- prefetch predicted data blocks plus following indirect blocks. */ zstream_t * dmu_zfetch_prepare(zfetch_t *zf, uint64_t blkid, uint64_t nblks, boolean_t fetch_data, boolean_t have_lock) { zstream_t *zs; spa_t *spa = zf->zf_dnode->dn_objset->os_spa; zfs_prefetch_type_t os_prefetch = zf->zf_dnode->dn_objset->os_prefetch; if (zfs_prefetch_disable || os_prefetch == ZFS_PREFETCH_NONE) return (NULL); if (os_prefetch == ZFS_PREFETCH_METADATA) fetch_data = B_FALSE; /* * If we haven't yet loaded the indirect vdevs' mappings, we * can only read from blocks that we carefully ensure are on * concrete vdevs (or previously-loaded indirect vdevs). So we * can't allow the predictive prefetcher to attempt reads of other * blocks (e.g. of the MOS's dnode object). */ if (!spa_indirect_vdevs_loaded(spa)) return (NULL); /* * As a fast path for small (single-block) files, ignore access * to the first block. */ if (!have_lock && blkid == 0) return (NULL); if (!have_lock) rw_enter(&zf->zf_dnode->dn_struct_rwlock, RW_READER); /* * A fast path for small files for which no prefetch will * happen. */ uint64_t maxblkid = zf->zf_dnode->dn_maxblkid; if (maxblkid < 2) { if (!have_lock) rw_exit(&zf->zf_dnode->dn_struct_rwlock); return (NULL); } mutex_enter(&zf->zf_lock); /* * Find perfect prefetch stream. Depending on whether the accesses * are block-aligned, first block of the new access may either follow * the last block of the previous access, or be equal to it. */ unsigned int dbs = zf->zf_dnode->dn_datablkshift; uint64_t end_blkid = blkid + nblks; for (zs = list_head(&zf->zf_stream); zs != NULL; zs = list_next(&zf->zf_stream, zs)) { if (blkid == zs->zs_blkid) { goto hit; } else if (blkid + 1 == zs->zs_blkid) { blkid++; nblks--; goto hit; } } /* * Find close enough prefetch stream. Access crossing stream position * is a hit in its new part. Access ahead of stream position considered * a hit for metadata prefetch, since we do not care about fill percent, * or stored for future otherwise. Access behind stream position is * silently ignored, since we already skipped it reaching fill percent. */ uint_t max_reorder = MIN((zfetch_max_reorder >> dbs) + 1, UINT16_MAX); uint_t t = gethrestime_sec() - zfetch_max_sec_reap; for (zs = list_head(&zf->zf_stream); zs != NULL; zs = list_next(&zf->zf_stream, zs)) { if (blkid > zs->zs_blkid) { if (end_blkid <= zs->zs_blkid + max_reorder) { if (!fetch_data) { nblks = dmu_zfetch_hit(zs, end_blkid - zs->zs_blkid); ZFETCHSTAT_BUMP(zfetchstat_stride); goto future; } nblks = dmu_zfetch_future(zs, blkid, nblks); if (nblks > 0) ZFETCHSTAT_BUMP(zfetchstat_stride); else ZFETCHSTAT_BUMP(zfetchstat_future); goto future; } } else if (end_blkid >= zs->zs_blkid) { nblks -= zs->zs_blkid - blkid; blkid += zs->zs_blkid - blkid; goto hit; } else if (end_blkid + max_reorder > zs->zs_blkid && (int)(zs->zs_atime - t) >= 0) { ZFETCHSTAT_BUMP(zfetchstat_past); zs->zs_atime = gethrestime_sec(); goto out; } } /* * This access is not part of any existing stream. Create a new * stream for it unless we are at the end of file. */ if (end_blkid < maxblkid) dmu_zfetch_stream_create(zf, end_blkid); mutex_exit(&zf->zf_lock); if (!have_lock) rw_exit(&zf->zf_dnode->dn_struct_rwlock); ZFETCHSTAT_BUMP(zfetchstat_misses); return (NULL); hit: nblks = dmu_zfetch_hit(zs, nblks); ZFETCHSTAT_BUMP(zfetchstat_hits); future: zs->zs_atime = gethrestime_sec(); /* Exit if we already prefetched for this position before. */ if (nblks == 0) goto out; /* If the file is ending, remove the stream. */ end_blkid = zs->zs_blkid; if (end_blkid >= maxblkid) { dmu_zfetch_stream_remove(zf, zs); out: mutex_exit(&zf->zf_lock); if (!have_lock) rw_exit(&zf->zf_dnode->dn_struct_rwlock); return (NULL); } /* * This access was to a block that we issued a prefetch for on * behalf of this stream. Calculate further prefetch distances. * * Start prefetch from the demand access size (nblks). Double the * distance every access up to zfetch_min_distance. After that only * if needed increase the distance by 1/8 up to zfetch_max_distance. * * Don't double the distance beyond single block if we have more * than ~6% of ARC held by active prefetches. It should help with * getting out of RAM on some badly mispredicted read patterns. */ unsigned int nbytes = nblks << dbs; unsigned int pf_nblks; if (fetch_data) { if (unlikely(zs->zs_pf_dist < nbytes)) zs->zs_pf_dist = nbytes; else if (zs->zs_pf_dist < zfetch_min_distance && (zs->zs_pf_dist < (1 << dbs) || aggsum_compare(&zfetch_sums.zfetchstat_io_active, arc_c_max >> (4 + dbs)) < 0)) zs->zs_pf_dist *= 2; else if (zs->zs_more) zs->zs_pf_dist += zs->zs_pf_dist / 8; zs->zs_more = B_FALSE; if (zs->zs_pf_dist > zfetch_max_distance) zs->zs_pf_dist = zfetch_max_distance; pf_nblks = zs->zs_pf_dist >> dbs; } else { pf_nblks = 0; } if (zs->zs_pf_start < end_blkid) zs->zs_pf_start = end_blkid; if (zs->zs_pf_end < end_blkid + pf_nblks) zs->zs_pf_end = end_blkid + pf_nblks; /* * Do the same for indirects, starting where we will stop reading * data blocks (and the indirects that point to them). */ if (unlikely(zs->zs_ipf_dist < nbytes)) zs->zs_ipf_dist = nbytes; else zs->zs_ipf_dist *= 2; if (zs->zs_ipf_dist > zfetch_max_idistance) zs->zs_ipf_dist = zfetch_max_idistance; pf_nblks = zs->zs_ipf_dist >> dbs; if (zs->zs_ipf_start < zs->zs_pf_end) zs->zs_ipf_start = zs->zs_pf_end; if (zs->zs_ipf_end < zs->zs_pf_end + pf_nblks) zs->zs_ipf_end = zs->zs_pf_end + pf_nblks; zfs_refcount_add(&zs->zs_refs, NULL); /* Count concurrent callers. */ zfs_refcount_add(&zs->zs_callers, NULL); mutex_exit(&zf->zf_lock); if (!have_lock) rw_exit(&zf->zf_dnode->dn_struct_rwlock); return (zs); } void dmu_zfetch_run(zfetch_t *zf, zstream_t *zs, boolean_t missed, boolean_t have_lock) { int64_t pf_start, pf_end, ipf_start, ipf_end; int epbs, issued; if (missed) zs->zs_missed = missed; /* * Postpone the prefetch if there are more concurrent callers. * It happens when multiple requests are waiting for the same * indirect block. The last one will run the prefetch for all. */ if (zfs_refcount_remove(&zs->zs_callers, NULL) != 0) { /* Drop reference taken in dmu_zfetch_prepare(). */ if (zfs_refcount_remove(&zs->zs_refs, NULL) == 0) dmu_zfetch_stream_fini(zs); return; } mutex_enter(&zf->zf_lock); if (zs->zs_missed) { pf_start = zs->zs_pf_start; pf_end = zs->zs_pf_start = zs->zs_pf_end; } else { pf_start = pf_end = 0; } ipf_start = zs->zs_ipf_start; ipf_end = zs->zs_ipf_start = zs->zs_ipf_end; mutex_exit(&zf->zf_lock); ASSERT3S(pf_start, <=, pf_end); ASSERT3S(ipf_start, <=, ipf_end); epbs = zf->zf_dnode->dn_indblkshift - SPA_BLKPTRSHIFT; ipf_start = P2ROUNDUP(ipf_start, 1 << epbs) >> epbs; ipf_end = P2ROUNDUP(ipf_end, 1 << epbs) >> epbs; ASSERT3S(ipf_start, <=, ipf_end); issued = pf_end - pf_start + ipf_end - ipf_start; if (issued > 1) { /* More references on top of taken in dmu_zfetch_prepare(). */ zfs_refcount_add_few(&zs->zs_refs, issued - 1, NULL); } else if (issued == 0) { /* Some other thread has done our work, so drop the ref. */ if (zfs_refcount_remove(&zs->zs_refs, NULL) == 0) dmu_zfetch_stream_fini(zs); return; } aggsum_add(&zfetch_sums.zfetchstat_io_active, issued); if (!have_lock) rw_enter(&zf->zf_dnode->dn_struct_rwlock, RW_READER); issued = 0; for (int64_t blk = pf_start; blk < pf_end; blk++) { issued += dbuf_prefetch_impl(zf->zf_dnode, 0, blk, ZIO_PRIORITY_ASYNC_READ, 0, dmu_zfetch_done, zs); } for (int64_t iblk = ipf_start; iblk < ipf_end; iblk++) { issued += dbuf_prefetch_impl(zf->zf_dnode, 1, iblk, ZIO_PRIORITY_ASYNC_READ, 0, dmu_zfetch_done, zs); } if (!have_lock) rw_exit(&zf->zf_dnode->dn_struct_rwlock); if (issued) ZFETCHSTAT_ADD(zfetchstat_io_issued, issued); } void dmu_zfetch(zfetch_t *zf, uint64_t blkid, uint64_t nblks, boolean_t fetch_data, boolean_t missed, boolean_t have_lock) { zstream_t *zs; zs = dmu_zfetch_prepare(zf, blkid, nblks, fetch_data, have_lock); if (zs) dmu_zfetch_run(zf, zs, missed, have_lock); } ZFS_MODULE_PARAM(zfs_prefetch, zfs_prefetch_, disable, INT, ZMOD_RW, "Disable all ZFS prefetching"); ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, max_streams, UINT, ZMOD_RW, "Max number of streams per zfetch"); ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, min_sec_reap, UINT, ZMOD_RW, "Min time before stream reclaim"); ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, max_sec_reap, UINT, ZMOD_RW, "Max time before stream delete"); ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, min_distance, UINT, ZMOD_RW, "Min bytes to prefetch per stream"); ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, max_distance, UINT, ZMOD_RW, "Max bytes to prefetch per stream"); ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, max_idistance, UINT, ZMOD_RW, "Max bytes to prefetch indirects for per stream"); ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, max_reorder, UINT, ZMOD_RW, "Max request reorder distance within a stream"); ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, hole_shift, UINT, ZMOD_RW, "Max log2 fraction of holes in a stream");