From 37f6845c6f86b1d04593e55d94318326006f4b5d Mon Sep 17 00:00:00 2001 From: Alexander Motin Date: Thu, 8 Sep 2022 13:30:53 -0400 Subject: [PATCH] Improve too large physical ashift handling When iterating through children physical ashifts for vdev, prefer ones above the maximum logical ashift, that we can actually use, but within the administrator defined maximum. When selecting top-level vdev ashift, do not set it to the defined maximum in case physical ashift is even higher, but just ignore one. Using the maximum does not prevent misaligned writes, but reduces space efficiency. Since ZFS tries to write data sequentially and aggregates the writes, in many cases large misanigned writes may be not as bad as the space penalty otherwise. Allow internal physical ashifts for vdevs higher than SHIFT_MAX. May be one day allocator or aggregation could benefit from that. Reduce zfs_vdev_max_auto_ashift default from 16 (64KB) to 14 (16KB), so that ZFS may still use bigger ashifts up to SHIFT_MAX (64KB), but only if it really has to or explicitly told to, but not as an "optimization". There are some read-intensive NVMe SSDs that report Preferred Write Alignment of 64KB, and attempt to build RAIDZ2 of those leads to a space inefficiency that can't be justified. Instead these changes make ZFS fall back to logical ashift of 12 (4KB) by default and only warn user that it may be suboptimal for performance. Reviewed-by: Brian Behlendorf Reviewed-by: Ryan Moeller Signed-off-by: Alexander Motin Sponsored by: iXsystems, Inc. Closes #13798 --- include/sys/vdev_impl.h | 1 + man/man4/zfs.4 | 5 ++- module/os/freebsd/zfs/vdev_geom.c | 3 +- module/zfs/vdev.c | 36 +++++++++++++++++-- module/zfs/vdev_draid.c | 10 ++++-- module/zfs/vdev_mirror.c | 10 ++++-- module/zfs/vdev_raidz.c | 10 ++++-- tests/zfs-tests/include/tunables.cfg | 2 ++ .../cli_root/zpool_add/add-o_ashift.ksh | 5 ++- 9 files changed, 69 insertions(+), 13 deletions(-) diff --git a/include/sys/vdev_impl.h b/include/sys/vdev_impl.h index d22abfbc2..470eaa763 100644 --- a/include/sys/vdev_impl.h +++ b/include/sys/vdev_impl.h @@ -641,6 +641,7 @@ extern int vdev_obsolete_counts_are_precise(vdev_t *vd, boolean_t *are_precise); */ int vdev_checkpoint_sm_object(vdev_t *vd, uint64_t *sm_obj); void vdev_metaslab_group_create(vdev_t *vd); +uint64_t vdev_best_ashift(uint64_t logical, uint64_t a, uint64_t b); /* * Vdev ashift optimization tunables diff --git a/man/man4/zfs.4 b/man/man4/zfs.4 index cc55ee32b..cecaf7e7f 100644 --- a/man/man4/zfs.4 +++ b/man/man4/zfs.4 @@ -347,9 +347,12 @@ When a vdev is added, target this number of metaslabs per top-level vdev. .It Sy zfs_vdev_default_ms_shift Ns = Ns Sy 29 Po 512 MiB Pc Pq int Default limit for metaslab size. . -.It Sy zfs_vdev_max_auto_ashift Ns = Ns Sy ASHIFT_MAX Po 16 Pc Pq ulong +.It Sy zfs_vdev_max_auto_ashift Ns = Ns Sy 14 Pq ulong Maximum ashift used when optimizing for logical \[->] physical sector size on new top-level vdevs. +May be increased up to +.Sy ASHIFT_MAX Po 16 Pc , +but this may negatively impact pool space efficiency. . .It Sy zfs_vdev_min_auto_ashift Ns = Ns Sy ASHIFT_MIN Po 9 Pc Pq ulong Minimum ashift used when creating new top-level vdevs. diff --git a/module/os/freebsd/zfs/vdev_geom.c b/module/os/freebsd/zfs/vdev_geom.c index f3b4846f4..fef6a1b88 100644 --- a/module/os/freebsd/zfs/vdev_geom.c +++ b/module/os/freebsd/zfs/vdev_geom.c @@ -955,8 +955,7 @@ skip_open: *logical_ashift = highbit(MAX(pp->sectorsize, SPA_MINBLOCKSIZE)) - 1; *physical_ashift = 0; if (pp->stripesize && pp->stripesize > (1 << *logical_ashift) && - ISP2(pp->stripesize) && pp->stripesize <= (1 << ASHIFT_MAX) && - pp->stripeoffset == 0) + ISP2(pp->stripesize) && pp->stripeoffset == 0) *physical_ashift = highbit(pp->stripesize) - 1; /* diff --git a/module/zfs/vdev.c b/module/zfs/vdev.c index ea0245610..048616c25 100644 --- a/module/zfs/vdev.c +++ b/module/zfs/vdev.c @@ -136,7 +136,15 @@ int zfs_vdev_standard_sm_blksz = (1 << 17); */ int zfs_nocacheflush = 0; -uint64_t zfs_vdev_max_auto_ashift = ASHIFT_MAX; +/* + * Maximum and minimum ashift values that can be automatically set based on + * vdev's physical ashift (disk's physical sector size). While ASHIFT_MAX + * is higher than the maximum value, it is intentionally limited here to not + * excessively impact pool space efficiency. Higher ashift values may still + * be forced by vdev logical ashift or by user via ashift property, but won't + * be set automatically as a performance optimization. + */ +uint64_t zfs_vdev_max_auto_ashift = 14; uint64_t zfs_vdev_min_auto_ashift = ASHIFT_MIN; void @@ -1845,6 +1853,24 @@ vdev_set_deflate_ratio(vdev_t *vd) } } +/* + * Choose the best of two ashifts, preferring one between logical ashift + * (absolute minimum) and administrator defined maximum, otherwise take + * the biggest of the two. + */ +uint64_t +vdev_best_ashift(uint64_t logical, uint64_t a, uint64_t b) +{ + if (a > logical && a <= zfs_vdev_max_auto_ashift) { + if (b <= logical || b > zfs_vdev_max_auto_ashift) + return (a); + else + return (MAX(a, b)); + } else if (b <= logical || b > zfs_vdev_max_auto_ashift) + return (MAX(a, b)); + return (b); +} + /* * Maximize performance by inflating the configured ashift for top level * vdevs to be as close to the physical ashift as possible while maintaining @@ -1856,7 +1882,8 @@ vdev_ashift_optimize(vdev_t *vd) { ASSERT(vd == vd->vdev_top); - if (vd->vdev_ashift < vd->vdev_physical_ashift) { + if (vd->vdev_ashift < vd->vdev_physical_ashift && + vd->vdev_physical_ashift <= zfs_vdev_max_auto_ashift) { vd->vdev_ashift = MIN( MAX(zfs_vdev_max_auto_ashift, vd->vdev_ashift), MAX(zfs_vdev_min_auto_ashift, @@ -4463,7 +4490,10 @@ vdev_get_stats_ex(vdev_t *vd, vdev_stat_t *vs, vdev_stat_ex_t *vsx) vs->vs_configured_ashift = vd->vdev_top != NULL ? vd->vdev_top->vdev_ashift : vd->vdev_ashift; vs->vs_logical_ashift = vd->vdev_logical_ashift; - vs->vs_physical_ashift = vd->vdev_physical_ashift; + if (vd->vdev_physical_ashift <= ASHIFT_MAX) + vs->vs_physical_ashift = vd->vdev_physical_ashift; + else + vs->vs_physical_ashift = 0; /* * Report fragmentation and rebuild progress for top-level, diff --git a/module/zfs/vdev_draid.c b/module/zfs/vdev_draid.c index 24034d9d9..24ea5d2cb 100644 --- a/module/zfs/vdev_draid.c +++ b/module/zfs/vdev_draid.c @@ -1496,8 +1496,14 @@ vdev_draid_calculate_asize(vdev_t *vd, uint64_t *asizep, uint64_t *max_asizep, asize = MIN(asize - 1, cvd->vdev_asize - 1) + 1; max_asize = MIN(max_asize - 1, cvd->vdev_max_asize - 1) + 1; logical_ashift = MAX(logical_ashift, cvd->vdev_ashift); - physical_ashift = MAX(physical_ashift, - cvd->vdev_physical_ashift); + } + for (int c = 0; c < vd->vdev_children; c++) { + vdev_t *cvd = vd->vdev_child[c]; + + if (cvd->vdev_ops == &vdev_draid_spare_ops) + continue; + physical_ashift = vdev_best_ashift(logical_ashift, + physical_ashift, cvd->vdev_physical_ashift); } *asizep = asize; diff --git a/module/zfs/vdev_mirror.c b/module/zfs/vdev_mirror.c index 3879de680..f9a01c9f5 100644 --- a/module/zfs/vdev_mirror.c +++ b/module/zfs/vdev_mirror.c @@ -409,8 +409,14 @@ vdev_mirror_open(vdev_t *vd, uint64_t *asize, uint64_t *max_asize, *asize = MIN(*asize - 1, cvd->vdev_asize - 1) + 1; *max_asize = MIN(*max_asize - 1, cvd->vdev_max_asize - 1) + 1; *logical_ashift = MAX(*logical_ashift, cvd->vdev_ashift); - *physical_ashift = MAX(*physical_ashift, - cvd->vdev_physical_ashift); + } + for (int c = 0; c < vd->vdev_children; c++) { + vdev_t *cvd = vd->vdev_child[c]; + + if (cvd->vdev_open_error) + continue; + *physical_ashift = vdev_best_ashift(*logical_ashift, + *physical_ashift, cvd->vdev_physical_ashift); } if (numerrors == vd->vdev_children) { diff --git a/module/zfs/vdev_raidz.c b/module/zfs/vdev_raidz.c index b4daf642e..5a44983e5 100644 --- a/module/zfs/vdev_raidz.c +++ b/module/zfs/vdev_raidz.c @@ -1527,8 +1527,14 @@ vdev_raidz_open(vdev_t *vd, uint64_t *asize, uint64_t *max_asize, *asize = MIN(*asize - 1, cvd->vdev_asize - 1) + 1; *max_asize = MIN(*max_asize - 1, cvd->vdev_max_asize - 1) + 1; *logical_ashift = MAX(*logical_ashift, cvd->vdev_ashift); - *physical_ashift = MAX(*physical_ashift, - cvd->vdev_physical_ashift); + } + for (c = 0; c < vd->vdev_children; c++) { + vdev_t *cvd = vd->vdev_child[c]; + + if (cvd->vdev_open_error != 0) + continue; + *physical_ashift = vdev_best_ashift(*logical_ashift, + *physical_ashift, cvd->vdev_physical_ashift); } *asize *= vd->vdev_children; diff --git a/tests/zfs-tests/include/tunables.cfg b/tests/zfs-tests/include/tunables.cfg index d6a2fe5db..80e7bcb3b 100644 --- a/tests/zfs-tests/include/tunables.cfg +++ b/tests/zfs-tests/include/tunables.cfg @@ -81,7 +81,9 @@ TRIM_TXG_BATCH trim.txg_batch zfs_trim_txg_batch TXG_HISTORY txg.history zfs_txg_history TXG_TIMEOUT txg.timeout zfs_txg_timeout UNLINK_SUSPEND_PROGRESS UNSUPPORTED zfs_unlink_suspend_progress +VDEV_FILE_LOGICAL_ASHIFT vdev.file.logical_ashift vdev_file_logical_ashift VDEV_FILE_PHYSICAL_ASHIFT vdev.file.physical_ashift vdev_file_physical_ashift +VDEV_MAX_AUTO_ASHIFT vdev.max_auto_ashift zfs_vdev_max_auto_ashift VDEV_MIN_MS_COUNT vdev.min_ms_count zfs_vdev_min_ms_count VDEV_VALIDATE_SKIP vdev.validate_skip vdev_validate_skip VOL_INHIBIT_DEV UNSUPPORTED zvol_inhibit_dev diff --git a/tests/zfs-tests/tests/functional/cli_root/zpool_add/add-o_ashift.ksh b/tests/zfs-tests/tests/functional/cli_root/zpool_add/add-o_ashift.ksh index 8d5ce5efa..0166e84ba 100755 --- a/tests/zfs-tests/tests/functional/cli_root/zpool_add/add-o_ashift.ksh +++ b/tests/zfs-tests/tests/functional/cli_root/zpool_add/add-o_ashift.ksh @@ -57,7 +57,9 @@ disk2=$TEST_BASE_DIR/disk2 log_must mkfile $SIZE $disk1 log_must mkfile $SIZE $disk2 +logical_ashift=$(get_tunable VDEV_FILE_LOGICAL_ASHIFT) orig_ashift=$(get_tunable VDEV_FILE_PHYSICAL_ASHIFT) +max_auto_ashift=$(get_tunable VDEV_MAX_AUTO_ASHIFT) typeset ashifts=("9" "10" "11" "12" "13" "14" "15" "16") for ashift in ${ashifts[@]} @@ -77,7 +79,8 @@ do log_must zpool create $TESTPOOL $disk1 log_must set_tunable64 VDEV_FILE_PHYSICAL_ASHIFT $ashift log_must zpool add $TESTPOOL $disk2 - log_must verify_ashift $disk2 $ashift + exp=$(( (ashift <= max_auto_ashift) ? ashift : logical_ashift )) + log_must verify_ashift $disk2 $exp # clean things for the next run log_must set_tunable64 VDEV_FILE_PHYSICAL_ASHIFT $orig_ashift