#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;
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 },
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;
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 =
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);
}
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);
dmu_zfetch_stream_create(zfetch_t *zf, uint64_t blkid)
{
zstream_t *zs, *zs_next, *zs_old = NULL;
- hrtime_t now = gethrtime(), t;
+ uint_t now = gethrestime_sec(), t;
ASSERT(MUTEX_HELD(&zf->zf_lock));
/*
* Delete too old streams, reusing the first found one.
*/
- t = now - SEC2NSEC(zfetch_max_sec_reap);
+ 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 (zfs_refcount_count(&zs->zs_refs) != 1)
+ if ((int)(zs->zs_atime - t) >= 0)
continue;
- if (zs->zs_atime > t)
+ if (zfs_refcount_count(&zs->zs_refs) != 1)
continue;
if (zs_old)
dmu_zfetch_stream_remove(zf, zs);
}
if (zs_old) {
zs = zs_old;
+ list_remove(&zf->zf_stream, zs);
goto reuse;
}
* 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 /
+ (zf->zf_dnode->dn_maxblkid << zf->zf_dnode->dn_datablkshift) /
zfetch_max_distance));
if (zf->zf_numstreams >= max_streams) {
- t = now - SEC2NSEC(zfetch_min_sec_reap);
+ t = now - 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)
+ if ((int)(zs->zs_atime - t) >= 0)
continue;
- if (zs->zs_atime > t)
+ if (zfs_refcount_count(&zs->zs_refs) != 1)
continue;
- if (zs_old == NULL || zs->zs_atime < zs_old->zs_atime)
+ 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);
}
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:
+ 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_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;
}
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;
+ }
+ } 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
mutex_enter(&zf->zf_lock);
/*
- * Find matching prefetch stream. Depending on whether the accesses
+ * 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) {
- break;
+ goto hit;
} else if (blkid + 1 == zs->zs_blkid) {
blkid++;
nblks--;
- break;
+ goto hit;
}
}
/*
- * 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.
+ * 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.
*/
- 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);
+ 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;
+ }
}
- /* 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);
- }
+ /*
+ * 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);
- 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);
+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);
- ZFETCHSTAT_BUMP(zfetchstat_misses);
return (NULL);
}
* 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) {
} 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;
+ 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
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);
if (!have_lock)
rw_exit(&zf->zf_dnode->dn_struct_rwlock);
-
- ZFETCHSTAT_BUMP(zfetchstat_hits);
return (zs);
}
void
-dmu_zfetch_run(zstream_t *zs, boolean_t missed, boolean_t have_lock)
+dmu_zfetch_run(zfetch_t *zf, zstream_t *zs, boolean_t missed,
+ boolean_t have_lock)
{
- zfetch_t *zf = zs->zs_fetch;
int64_t pf_start, pf_end, ipf_start, ipf_end;
int epbs, issued;
zs = dmu_zfetch_prepare(zf, blkid, nblks, fetch_data, have_lock);
if (zs)
- dmu_zfetch_run(zs, missed, have_lock);
+ dmu_zfetch_run(zf, zs, missed, have_lock);
}
ZFS_MODULE_PARAM(zfs_prefetch, zfs_prefetch_, disable, INT, ZMOD_RW,
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");
projects / mirror_zfs.git / commitdiff