* 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 http://www.opensolaris.org/os/licensing.
+ * or https://opensource.org/licenses/CDDL-1.0.
* See the License for the specific language governing permissions
* and limitations under the License.
*
*/
/*
- * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2013, 2017 by Delphix. All rights reserved.
*/
#include <sys/zfs_context.h>
+#include <sys/arc_impl.h>
#include <sys/dnode.h>
#include <sys/dmu_objset.h>
#include <sys/dmu_zfetch.h>
#include <sys/dmu.h>
#include <sys/dbuf.h>
#include <sys/kstat.h>
+#include <sys/wmsum.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;
+static int zfs_prefetch_disable = B_FALSE;
/* max # of streams per zfetch */
-unsigned int zfetch_max_streams = 8;
+static unsigned int zfetch_max_streams = 8;
/* min time before stream reclaim */
-unsigned int zfetch_min_sec_reap = 2;
-/* max number of blocks to fetch at a time */
-unsigned int zfetch_block_cap = 256;
-/* number of bytes in a array_read at which we stop prefetching (1Mb) */
-unsigned long zfetch_array_rd_sz = 1024 * 1024;
-
-/* 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 *);
+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;
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;
+ 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 },
{ "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 },
+ { "io_issued", KSTAT_DATA_UINT64 },
+ { "io_active", 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);
+struct {
+ wmsum_t zfetchstat_hits;
+ wmsum_t zfetchstat_misses;
+ wmsum_t zfetchstat_max_streams;
+ wmsum_t zfetchstat_io_issued;
+ aggsum_t zfetchstat_io_active;
+} zfetch_sums;
-kstat_t *zfetch_ksp;
+#define ZFETCHSTAT_BUMP(stat) \
+ wmsum_add(&zfetch_sums.stat, 1)
+#define ZFETCHSTAT_ADD(stat, val) \
+ wmsum_add(&zfetch_sums.stat, val)
-/*
- * 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);
-}
+static kstat_t *zfetch_ksp;
-/*
- * 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)
+static int
+zfetch_kstats_update(kstat_t *ksp, int rw)
{
- 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();
+ 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_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_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),
if (zfetch_ksp != NULL) {
zfetch_ksp->ks_data = &zfetch_stats;
+ zfetch_ksp->ks_update = zfetch_kstats_update;
kstat_install(zfetch_ksp);
}
}
kstat_delete(zfetch_ksp);
zfetch_ksp = NULL;
}
+
+ wmsum_fini(&zfetch_sums.zfetchstat_hits);
+ 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);
}
/*
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;
+ zf->zf_numstreams = 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);
+ mutex_init(&zf->zf_lock, NULL, MUTEX_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)
+static void
+dmu_zfetch_stream_fini(zstream_t *zs)
{
- uint64_t fetchsz;
- uint64_t i;
-
- fetchsz = dmu_zfetch_fetchsz(dn, blkid, nblks);
-
- for (i = 0; i < fetchsz; i++) {
- dbuf_prefetch(dn, blkid + i, ZIO_PRIORITY_ASYNC_READ);
- }
+ ASSERT(!list_link_active(&zs->zs_node));
+ zfs_refcount_destroy(&zs->zs_callers);
+ zfs_refcount_destroy(&zs->zs_refs);
+ kmem_free(zs, sizeof (*zs));
+}
- return (fetchsz);
+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);
}
/*
- * 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.
+ * 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.
*/
-static uint64_t
-dmu_zfetch_fetchsz(dnode_t *dn, uint64_t blkid, uint64_t nblks)
+void
+dmu_zfetch_fini(zfetch_t *zf)
{
- 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;
- }
+ 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);
- return (fetchsz);
+ zf->zf_dnode = NULL;
}
/*
- * 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
+ * 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 boolean_t
-dmu_zfetch_find(zfetch_t *zf, zstream_t *zh, int prefetched)
+static void
+dmu_zfetch_stream_create(zfetch_t *zf, uint64_t blkid)
{
- zstream_t *zs;
- int64_t diff;
- int reset = !prefetched;
- int rc = 0;
+ zstream_t *zs, *zs_next, *zs_old = NULL;
+ hrtime_t now = gethrtime(), t;
- if (zh == NULL)
- return (0);
+ ASSERT(MUTEX_HELD(&zf->zf_lock));
/*
- * 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.
+ * Delete too old streams, reusing the first found one.
*/
-
- rw_enter(&zf->zf_rwlock, RW_READER);
-top:
-
- for (zs = list_head(&zf->zf_stream); zs;
- zs = list_next(&zf->zf_stream, zs)) {
-
+ t = now - SEC2NSEC(zfetch_max_sec_reap);
+ for (zs = list_head(&zf->zf_stream); zs != NULL; zs = zs_next) {
+ zs_next = list_next(&zf->zf_stream, zs);
/*
- * XXX - should this be an assert?
+ * Skip if still active. 1 -- zf_stream reference.
*/
- if (zs->zst_len == 0) {
- /* bogus stream */
- ZFETCHSTAT_BUMP(zfetchstat_bogus_streams);
+ if (zfs_refcount_count(&zs->zs_refs) != 1)
continue;
- }
+ if (zs->zs_atime > t)
+ continue;
+ if (zs_old)
+ dmu_zfetch_stream_remove(zf, zs);
+ else
+ zs_old = zs;
+ }
+ if (zs_old) {
+ zs = zs_old;
+ goto reuse;
+ }
- /*
- * 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);
- }
+ /*
+ * 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_datablksz /
+ zfetch_max_distance));
+ if (zf->zf_numstreams >= max_streams) {
+ t = now - SEC2NSEC(zfetch_min_sec_reap);
+ for (zs = list_head(&zf->zf_stream); zs != NULL;
+ zs = list_next(&zf->zf_stream, zs)) {
+ if (zfs_refcount_count(&zs->zs_refs) != 1)
+ continue;
+ if (zs->zs_atime > t)
+ continue;
+ if (zs_old == NULL || zs->zs_atime < zs_old->zs_atime)
+ zs_old = zs;
}
-
- /*
- * 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;
-
- mutex_enter(&zs->zst_lock);
-
- 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;
-
- mutex_enter(&zs->zst_lock);
-
- 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 */
-
- mutex_enter(&zs->zst_lock);
-
- 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 */
-
- mutex_enter(&zs->zst_lock);
-
- 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_old) {
+ zs = zs_old;
+ goto reuse;
}
+ ZFETCHSTAT_BUMP(zfetchstat_max_streams);
+ return;
}
- 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);
+ zs = kmem_zalloc(sizeof (*zs), KM_SLEEP);
+ zs->zs_fetch = zf;
+ 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++;
+ list_insert_head(&zf->zf_stream, zs);
+
+reuse:
+ zs->zs_blkid = blkid;
+ zs->zs_pf_dist = 0;
+ zs->zs_pf_start = blkid;
+ zs->zs_pf_end = blkid;
+ zs->zs_ipf_dist = 0;
+ zs->zs_ipf_start = blkid;
+ zs->zs_ipf_end = blkid;
+ /* Allow immediate stream reuse until first hit. */
+ zs->zs_atime = now - SEC2NSEC(zfetch_min_sec_reap);
+ zs->zs_missed = B_FALSE;
+ zs->zs_more = B_FALSE;
}
-/*
- * 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.
- */
-void
-dmu_zfetch_rele(zfetch_t *zf)
+static void
+dmu_zfetch_done(void *arg, uint64_t level, uint64_t blkid, boolean_t io_issued)
{
- zstream_t *zs;
- zstream_t *zs_next;
-
- 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));
- }
- list_destroy(&zf->zf_stream);
- rw_destroy(&zf->zf_rwlock);
+ zstream_t *zs = arg;
- zf->zf_dnode = NULL;
+ 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);
}
/*
- * 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.
+ * 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.
*/
-static int
-dmu_zfetch_stream_insert(zfetch_t *zf, zstream_t *zs)
+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_walk;
- zstream_t *zs_next;
-
- ASSERT(RW_WRITE_HELD(&zf->zf_rwlock));
+ 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;
- for (zs_walk = list_head(&zf->zf_stream); zs_walk; zs_walk = zs_next) {
- zs_next = list_next(&zf->zf_stream, zs_walk);
+ if (zfs_prefetch_disable || os_prefetch == ZFS_PREFETCH_NONE)
+ return (NULL);
- if (dmu_zfetch_streams_equal(zs_walk, zs)) {
- return (0);
- }
- }
+ if (os_prefetch == ZFS_PREFETCH_METADATA)
+ fetch_data = B_FALSE;
- list_insert_head(&zf->zf_stream, zs);
- zf->zf_stream_cnt++;
- return (1);
-}
+ /*
+ * 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);
-/*
- * 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;
+ if (!have_lock)
+ rw_enter(&zf->zf_dnode->dn_struct_rwlock, RW_READER);
- if (! rw_tryenter(&zf->zf_rwlock, RW_WRITER))
- return (0);
+ /*
+ * 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);
- for (zs = list_head(&zf->zf_stream); zs;
+ /*
+ * Find matching 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.
+ */
+ for (zs = list_head(&zf->zf_stream); zs != NULL;
zs = list_next(&zf->zf_stream, zs)) {
-
- if (((ddi_get_lbolt() - zs->zst_last)/hz) > zfetch_min_sec_reap)
+ if (blkid == zs->zs_blkid) {
+ break;
+ } else if (blkid + 1 == zs->zs_blkid) {
+ blkid++;
+ nblks--;
break;
+ }
}
- if (zs) {
- dmu_zfetch_stream_remove(zf, zs);
- mutex_destroy(&zs->zst_lock);
- bzero(zs, sizeof (zstream_t));
- } else {
- zf->zf_alloc_fail++;
+ /*
+ * If the file is ending, remove the matching stream if found.
+ * If not found then it is too late to create a new one now.
+ */
+ uint64_t end_of_access_blkid = blkid + nblks;
+ if (end_of_access_blkid >= maxblkid) {
+ if (zs != NULL)
+ dmu_zfetch_stream_remove(zf, zs);
+ mutex_exit(&zf->zf_lock);
+ if (!have_lock)
+ rw_exit(&zf->zf_dnode->dn_struct_rwlock);
+ return (NULL);
}
- 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);
-
- if (zs1->zst_ph_offset != zs2->zst_ph_offset)
- return (0);
+ /* Exit if we already prefetched this block before. */
+ if (nblks == 0) {
+ mutex_exit(&zf->zf_lock);
+ if (!have_lock)
+ rw_exit(&zf->zf_dnode->dn_struct_rwlock);
+ return (NULL);
+ }
- if (zs1->zst_cap != zs2->zst_cap)
- return (0);
+ if (zs == NULL) {
+ /*
+ * This access is not part of any existing stream. Create
+ * a new stream for it.
+ */
+ dmu_zfetch_stream_create(zf, end_of_access_blkid);
+ mutex_exit(&zf->zf_lock);
+ if (!have_lock)
+ rw_exit(&zf->zf_dnode->dn_struct_rwlock);
+ ZFETCHSTAT_BUMP(zfetchstat_misses);
+ return (NULL);
+ }
- if (zs1->zst_direction != zs2->zst_direction)
- return (0);
+ /*
+ * 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 dbs = zf->zf_dnode->dn_datablkshift;
+ 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_of_access_blkid)
+ zs->zs_pf_start = end_of_access_blkid;
+ if (zs->zs_pf_end < end_of_access_blkid + pf_nblks)
+ zs->zs_pf_end = end_of_access_blkid + pf_nblks;
- return (1);
+ /*
+ * 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;
+
+ zs->zs_blkid = end_of_access_blkid;
+ /* Protect the stream from reclamation. */
+ zs->zs_atime = gethrtime();
+ 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);
+
+ ZFETCHSTAT_BUMP(zfetchstat_hits);
+ return (zs);
}
-/*
- * This is the prefetch entry point. It calls all of the other dmu_zfetch
- * routines to create, delete, find, or operate upon prefetch streams.
- */
void
-dmu_zfetch(zfetch_t *zf, uint64_t offset, uint64_t size, int prefetched)
+dmu_zfetch_run(zstream_t *zs, boolean_t missed, boolean_t have_lock)
{
- zstream_t zst;
- zstream_t *newstream;
- boolean_t fetched;
- int inserted;
- unsigned int blkshft;
- uint64_t blksz;
-
- if (zfs_prefetch_disable)
- return;
-
- /* files that aren't ln2 blocksz are only one block -- nothing to do */
- if (!zf->zf_dnode->dn_datablkshift)
- return;
+ zfetch_t *zf = zs->zs_fetch;
+ int64_t pf_start, pf_end, ipf_start, ipf_end;
+ int epbs, issued;
- /* convert offset and size, into blockid and nblocks */
- blkshft = zf->zf_dnode->dn_datablkshift;
- blksz = (1 << blkshft);
+ if (missed)
+ zs->zs_missed = missed;
- bzero(&zst, sizeof (zstream_t));
- zst.zst_offset = offset >> blkshft;
- zst.zst_len = (P2ROUNDUP(offset + size, blksz) -
- P2ALIGN(offset, blksz)) >> blkshft;
+ /*
+ * 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;
+ }
- fetched = dmu_zfetch_find(zf, &zst, prefetched);
- if (fetched) {
- ZFETCHSTAT_BUMP(zfetchstat_hits);
+ 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 {
- ZFETCHSTAT_BUMP(zfetchstat_misses);
- if ((fetched = dmu_zfetch_colinear(zf, &zst))) {
- ZFETCHSTAT_BUMP(zfetchstat_colinear_hits);
- } else {
- ZFETCHSTAT_BUMP(zfetchstat_colinear_misses);
- }
+ 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 (!fetched) {
- newstream = dmu_zfetch_stream_reclaim(zf);
+ if (!have_lock)
+ rw_enter(&zf->zf_dnode->dn_struct_rwlock, RW_READER);
- /*
- * we still couldn't find a stream, drop the lock, and allocate
- * one if possible. Otherwise, give up and go home.
- */
- if (newstream) {
- ZFETCHSTAT_BUMP(zfetchstat_reclaim_successes);
- } else {
- uint64_t maxblocks;
- uint32_t max_streams;
- uint32_t cur_streams;
-
- ZFETCHSTAT_BUMP(zfetchstat_reclaim_failures);
- cur_streams = zf->zf_stream_cnt;
- maxblocks = zf->zf_dnode->dn_maxblkid;
-
- max_streams = MIN(zfetch_max_streams,
- (maxblocks / zfetch_block_cap));
- if (max_streams == 0) {
- max_streams++;
- }
-
- if (cur_streams >= max_streams) {
- return;
- }
- newstream =
- kmem_zalloc(sizeof (zstream_t), KM_PUSHPAGE);
- }
+ 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);
+ }
- newstream->zst_offset = zst.zst_offset;
- newstream->zst_len = zst.zst_len;
- newstream->zst_stride = zst.zst_len;
- newstream->zst_ph_offset = zst.zst_len + zst.zst_offset;
- newstream->zst_cap = zst.zst_len;
- newstream->zst_direction = ZFETCH_FORWARD;
- newstream->zst_last = ddi_get_lbolt();
+ if (!have_lock)
+ rw_exit(&zf->zf_dnode->dn_struct_rwlock);
- mutex_init(&newstream->zst_lock, NULL, MUTEX_DEFAULT, NULL);
+ if (issued)
+ ZFETCHSTAT_ADD(zfetchstat_io_issued, issued);
+}
- rw_enter(&zf->zf_rwlock, RW_WRITER);
- inserted = dmu_zfetch_stream_insert(zf, newstream);
- rw_exit(&zf->zf_rwlock);
+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;
- if (!inserted) {
- mutex_destroy(&newstream->zst_lock);
- kmem_free(newstream, sizeof (zstream_t));
- }
- }
+ zs = dmu_zfetch_prepare(zf, blkid, nblks, fetch_data, have_lock);
+ if (zs)
+ dmu_zfetch_run(zs, missed, have_lock);
}
-#if defined(_KERNEL) && defined(HAVE_SPL)
-module_param(zfs_prefetch_disable, int, 0644);
-MODULE_PARM_DESC(zfs_prefetch_disable, "Disable all ZFS prefetching");
+ZFS_MODULE_PARAM(zfs_prefetch, zfs_prefetch_, disable, INT, ZMOD_RW,
+ "Disable all ZFS prefetching");
-module_param(zfetch_max_streams, uint, 0644);
-MODULE_PARM_DESC(zfetch_max_streams, "Max number of streams per zfetch");
+ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, max_streams, UINT, ZMOD_RW,
+ "Max number of streams per zfetch");
-module_param(zfetch_min_sec_reap, uint, 0644);
-MODULE_PARM_DESC(zfetch_min_sec_reap, "Min time before stream reclaim");
+ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, min_sec_reap, UINT, ZMOD_RW,
+ "Min time before stream reclaim");
-module_param(zfetch_block_cap, uint, 0644);
-MODULE_PARM_DESC(zfetch_block_cap, "Max number of blocks to fetch at a time");
+ZFS_MODULE_PARAM(zfs_prefetch, zfetch_, max_sec_reap, UINT, ZMOD_RW,
+ "Max time before stream delete");
-module_param(zfetch_array_rd_sz, ulong, 0644);
-MODULE_PARM_DESC(zfetch_array_rd_sz, "Number of bytes in a array_read");
-#endif
+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");
projects / mirror_zfs.git / blobdiff