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Set aside a metaslab for ZIL blocks

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Mixing ZIL and normal allocations has several problems:

1. The ZIL allocations are allocated, written to disk, and then a few
seconds later freed.  This leaves behind holes (free segments) where the
ZIL blocks used to be, which increases fragmentation, which negatively
impacts performance.

2. When under moderate load, ZIL allocations are of 128KB.  If the pool
is fairly fragmented, there may not be many free chunks of that size.
This causes ZFS to load more metaslabs to locate free segments of 128KB
or more.  The loading happens synchronously (from zil_commit()), and can
take around a second even if the metaslab's spacemap is cached in the
ARC.  All concurrent synchronous operations on this filesystem must wait
while the metaslab is loading.  This can cause a significant performance
impact.

3. If the pool is very fragmented, there may be zero free chunks of
128KB or more.  In this case, the ZIL falls back to txg_wait_synced(),
which has an enormous performance impact.

These problems can be eliminated by using a dedicated log device
("slog"), even one with the same performance characteristics as the
normal devices.

This change sets aside one metaslab from each top-level vdev that is
preferentially used for ZIL allocations (vdev_log_mg,
spa_embedded_log_class).  From an allocation perspective, this is
similar to having a dedicated log device, and it eliminates the
above-mentioned performance problems.

Log (ZIL) blocks can be allocated from the following locations.  Each
one is tried in order until the allocation succeeds:
1. dedicated log vdevs, aka "slog" (spa_log_class)
2. embedded slog metaslabs (spa_embedded_log_class)
3. other metaslabs in normal vdevs (spa_normal_class)

The space required for the embedded slog metaslabs is usually between
0.5% and 1.0% of the pool, and comes out of the existing 3.2% of "slop"
space that is not available for user data.

On an all-ssd system with 4TB storage, 87% fragmentation, 60% capacity,
and recordsize=8k, testing shows a ~50% performance increase on random
8k sync writes.  On even more fragmented systems (which hit problem #3
above and call txg_wait_synced()), the performance improvement can be
arbitrarily large (>100x).

Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Reviewed-by: George Wilson <gwilson@delphix.com>
Reviewed-by: Don Brady <don.brady@delphix.com>
Reviewed-by: Mark Maybee <mark.maybee@delphix.com>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes #11389
This commit is contained in:
Matthew Ahrens 2021-01-21 15:12:54 -08:00 committed by GitHub
parent 984362a71e
commit aa755b3549
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
14 changed files with 357 additions and 103 deletions
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21
cmd/zdb/zdb.c
View File

@ -5844,6 +5844,7 @@ zdb_leak_init_prepare_indirect_vdevs(spa_t *spa, zdb_cb_t *zcb)
* metaslabs. We want to set them up for
* zio_claim().
*/
vdev_metaslab_group_create(vd);
VERIFY0(vdev_metaslab_init(vd, 0));
vdev_indirect_mapping_t *vim = vd->vdev_indirect_mapping;
@ -5882,6 +5883,7 @@ zdb_leak_init(spa_t *spa, zdb_cb_t *zcb)
*/
spa->spa_normal_class->mc_ops = &zdb_metaslab_ops;
spa->spa_log_class->mc_ops = &zdb_metaslab_ops;
spa->spa_embedded_log_class->mc_ops = &zdb_metaslab_ops;
zcb->zcb_vd_obsolete_counts =
umem_zalloc(rvd->vdev_children * sizeof (uint32_t *),
@ -6015,7 +6017,6 @@ zdb_leak_fini(spa_t *spa, zdb_cb_t *zcb)
vdev_t *rvd = spa->spa_root_vdev;
for (unsigned c = 0; c < rvd->vdev_children; c++) {
vdev_t *vd = rvd->vdev_child[c];
metaslab_group_t *mg __maybe_unused = vd->vdev_mg;
if (zcb->zcb_vd_obsolete_counts[c] != NULL) {
leaks |= zdb_check_for_obsolete_leaks(vd, zcb);
@ -6023,7 +6024,9 @@ zdb_leak_fini(spa_t *spa, zdb_cb_t *zcb)
for (uint64_t m = 0; m < vd->vdev_ms_count; m++) {
metaslab_t *msp = vd->vdev_ms[m];
ASSERT3P(mg, ==, msp->ms_group);
ASSERT3P(msp->ms_group, ==, (msp->ms_group->mg_class ==
spa_embedded_log_class(spa)) ?
vd->vdev_log_mg : vd->vdev_mg);
/*
* ms_allocatable has been overloaded
@ -6230,6 +6233,8 @@ dump_block_stats(spa_t *spa)
zcb.zcb_totalasize = metaslab_class_get_alloc(spa_normal_class(spa));
zcb.zcb_totalasize += metaslab_class_get_alloc(spa_special_class(spa));
zcb.zcb_totalasize += metaslab_class_get_alloc(spa_dedup_class(spa));
zcb.zcb_totalasize +=
metaslab_class_get_alloc(spa_embedded_log_class(spa));
zcb.zcb_start = zcb.zcb_lastprint = gethrtime();
err = traverse_pool(spa, 0, flags, zdb_blkptr_cb, &zcb);
@ -6277,6 +6282,7 @@ dump_block_stats(spa_t *spa)
total_alloc = norm_alloc +
metaslab_class_get_alloc(spa_log_class(spa)) +
metaslab_class_get_alloc(spa_embedded_log_class(spa)) +
metaslab_class_get_alloc(spa_special_class(spa)) +
metaslab_class_get_alloc(spa_dedup_class(spa)) +
get_unflushed_alloc_space(spa);
@ -6344,6 +6350,17 @@ dump_block_stats(spa_t *spa)
100.0 * alloc / space);
}
if (spa_embedded_log_class(spa)->mc_allocator[0].mca_rotor != NULL) {
uint64_t alloc = metaslab_class_get_alloc(
spa_embedded_log_class(spa));
uint64_t space = metaslab_class_get_space(
spa_embedded_log_class(spa));
(void) printf("\t%-16s %14llu used: %5.2f%%\n",
"Embedded log class", (u_longlong_t)alloc,
100.0 * alloc / space);
}
for (i = 0; i < NUM_BP_EMBEDDED_TYPES; i++) {
if (zcb.zcb_embedded_blocks[i] == 0)
continue;

3
include/sys/dmu.h
View File

@ -142,9 +142,6 @@ typedef enum dmu_object_byteswap {
#define DMU_OT_IS_DDT(ot) \
((ot) == DMU_OT_DDT_ZAP)
#define DMU_OT_IS_ZIL(ot) \
((ot) == DMU_OT_INTENT_LOG)
/* Note: ztest uses DMU_OT_UINT64_OTHER as a proxy for file blocks */
#define DMU_OT_IS_FILE(ot) \
((ot) == DMU_OT_PLAIN_FILE_CONTENTS || (ot) == DMU_OT_UINT64_OTHER)

1
include/sys/spa.h
View File

@ -1047,6 +1047,7 @@ extern uint64_t spa_version(spa_t *spa);
extern boolean_t spa_deflate(spa_t *spa);
extern metaslab_class_t *spa_normal_class(spa_t *spa);
extern metaslab_class_t *spa_log_class(spa_t *spa);
extern metaslab_class_t *spa_embedded_log_class(spa_t *spa);
extern metaslab_class_t *spa_special_class(spa_t *spa);
extern metaslab_class_t *spa_dedup_class(spa_t *spa);
extern metaslab_class_t *spa_preferred_class(spa_t *spa, uint64_t size,

1
include/sys/spa_impl.h
View File

@ -226,6 +226,7 @@ struct spa {
boolean_t spa_is_exporting; /* true while exporting pool */
metaslab_class_t *spa_normal_class; /* normal data class */
metaslab_class_t *spa_log_class; /* intent log data class */
metaslab_class_t *spa_embedded_log_class; /* log on normal vdevs */
metaslab_class_t *spa_special_class; /* special allocation class */
metaslab_class_t *spa_dedup_class; /* dedup allocation class */
uint64_t spa_first_txg; /* first txg after spa_open() */

4
include/sys/vdev.h
View File

@ -33,6 +33,7 @@
#include <sys/zio.h>
#include <sys/dmu.h>
#include <sys/space_map.h>
#include <sys/metaslab.h>
#include <sys/fs/zfs.h>
#ifdef __cplusplus
@ -113,6 +114,9 @@ extern void vdev_xlate_walk(vdev_t *vd, const range_seg64_t *logical_rs,
vdev_xlate_func_t *func, void *arg);
extern void vdev_get_stats_ex(vdev_t *vd, vdev_stat_t *vs, vdev_stat_ex_t *vsx);
extern metaslab_group_t *vdev_get_mg(vdev_t *vd, metaslab_class_t *mc);
extern void vdev_get_stats(vdev_t *vd, vdev_stat_t *vs);
extern void vdev_clear_stats(vdev_t *vd);
extern void vdev_stat_update(zio_t *zio, uint64_t psize);

2
include/sys/vdev_impl.h
View File

@ -280,6 +280,7 @@ struct vdev {
uint64_t vdev_ms_shift; /* metaslab size shift */
uint64_t vdev_ms_count; /* number of metaslabs */
metaslab_group_t *vdev_mg; /* metaslab group */
metaslab_group_t *vdev_log_mg; /* embedded slog metaslab group */
metaslab_t **vdev_ms; /* metaslab array */
uint64_t vdev_pending_fastwrite; /* allocated fastwrites */
txg_list_t vdev_ms_list; /* per-txg dirty metaslab lists */
@ -636,6 +637,7 @@ extern int vdev_obsolete_counts_are_precise(vdev_t *vd, boolean_t *are_precise);
* Other miscellaneous functions
*/
int vdev_checkpoint_sm_object(vdev_t *vd, uint64_t *sm_obj);
void vdev_metaslab_group_create(vdev_t *vd);
/*
* Vdev ashift optimization tunables

1
include/sys/zfs_debug.h
View File

@ -56,6 +56,7 @@ extern int zfs_dbgmsg_enable;
#define ZFS_DEBUG_INDIRECT_REMAP (1 << 10)
#define ZFS_DEBUG_TRIM (1 << 11)
#define ZFS_DEBUG_LOG_SPACEMAP (1 << 12)
#define ZFS_DEBUG_METASLAB_ALLOC (1 << 13)
extern void __set_error(const char *file, const char *func, int line, int err);
extern void __zfs_dbgmsg(char *buf);

16
man/man5/zfs-module-parameters.5
View File

@ -3936,6 +3936,22 @@ to limit potential SLOG device abuse by single active ZIL writer.
Default value: \fB786,432\fR.
.RE
.sp
.ne 2
.na
\fBzfs_embedded_slog_min_ms\fR (int)
.ad
.RS 12n
Usually, one metaslab from each (normal-class) vdev is dedicated for use by
the ZIL (to log synchronous writes).
However, if there are fewer than zfs_embedded_slog_min_ms metaslabs in the
vdev, this functionality is disabled.
This ensures that we don't set aside an unreasonable amount of space for the
ZIL.
.sp
Default value: \fB64\fR.
.RE
.sp
.ne 2
.na

62
module/zfs/metaslab.c
View File

@ -524,7 +524,7 @@ metaslab_class_histogram_verify(metaslab_class_t *mc)
for (int c = 0; c < rvd->vdev_children; c++) {
vdev_t *tvd = rvd->vdev_child[c];
metaslab_group_t *mg = tvd->vdev_mg;
metaslab_group_t *mg = vdev_get_mg(tvd, mc);
/*
* Skip any holes, uninitialized top-levels, or
@ -535,12 +535,16 @@ metaslab_class_histogram_verify(metaslab_class_t *mc)
continue;
}
IMPLY(mg == mg->mg_vd->vdev_log_mg,
mc == spa_embedded_log_class(mg->mg_vd->vdev_spa));
for (i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i++)
mc_hist[i] += mg->mg_histogram[i];
}
for (i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i++)
for (i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i++) {
VERIFY3U(mc_hist[i], ==, mc->mc_histogram[i]);
}
kmem_free(mc_hist, sizeof (uint64_t) * RANGE_TREE_HISTOGRAM_SIZE);
}
@ -1004,16 +1008,22 @@ metaslab_group_initialized(metaslab_group_t *mg)
uint64_t
metaslab_group_get_space(metaslab_group_t *mg)
{
return ((1ULL << mg->mg_vd->vdev_ms_shift) * mg->mg_vd->vdev_ms_count);
/*
* Note that the number of nodes in mg_metaslab_tree may be one less
* than vdev_ms_count, due to the embedded log metaslab.
*/
mutex_enter(&mg->mg_lock);
uint64_t ms_count = avl_numnodes(&mg->mg_metaslab_tree);
mutex_exit(&mg->mg_lock);
return ((1ULL << mg->mg_vd->vdev_ms_shift) * ms_count);
}
void
metaslab_group_histogram_verify(metaslab_group_t *mg)
{
uint64_t *mg_hist;
vdev_t *vd = mg->mg_vd;
uint64_t ashift = vd->vdev_ashift;
int i;
avl_tree_t *t = &mg->mg_metaslab_tree;
uint64_t ashift = mg->mg_vd->vdev_ashift;
if ((zfs_flags & ZFS_DEBUG_HISTOGRAM_VERIFY) == 0)
return;
@ -1024,21 +1034,25 @@ metaslab_group_histogram_verify(metaslab_group_t *mg)
ASSERT3U(RANGE_TREE_HISTOGRAM_SIZE, >=,
SPACE_MAP_HISTOGRAM_SIZE + ashift);
for (int m = 0; m < vd->vdev_ms_count; m++) {
metaslab_t *msp = vd->vdev_ms[m];
/* skip if not active or not a member */
if (msp->ms_sm == NULL || msp->ms_group != mg)
mutex_enter(&mg->mg_lock);
for (metaslab_t *msp = avl_first(t);
msp != NULL; msp = AVL_NEXT(t, msp)) {
VERIFY3P(msp->ms_group, ==, mg);
/* skip if not active */
if (msp->ms_sm == NULL)
continue;
for (i = 0; i < SPACE_MAP_HISTOGRAM_SIZE; i++)
for (int i = 0; i < SPACE_MAP_HISTOGRAM_SIZE; i++) {
mg_hist[i + ashift] +=
msp->ms_sm->sm_phys->smp_histogram[i];
}
}
for (i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i ++)
for (int i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i ++)
VERIFY3U(mg_hist[i], ==, mg->mg_histogram[i]);
mutex_exit(&mg->mg_lock);
kmem_free(mg_hist, sizeof (uint64_t) * RANGE_TREE_HISTOGRAM_SIZE);
}
@ -1054,6 +1068,8 @@ metaslab_group_histogram_add(metaslab_group_t *mg, metaslab_t *msp)
mutex_enter(&mg->mg_lock);
for (int i = 0; i < SPACE_MAP_HISTOGRAM_SIZE; i++) {
IMPLY(mg == mg->mg_vd->vdev_log_mg,
mc == spa_embedded_log_class(mg->mg_vd->vdev_spa));
mg->mg_histogram[i + ashift] +=
msp->ms_sm->sm_phys->smp_histogram[i];
mc->mc_histogram[i + ashift] +=
@ -1078,6 +1094,8 @@ metaslab_group_histogram_remove(metaslab_group_t *mg, metaslab_t *msp)
msp->ms_sm->sm_phys->smp_histogram[i]);
ASSERT3U(mc->mc_histogram[i + ashift], >=,
msp->ms_sm->sm_phys->smp_histogram[i]);
IMPLY(mg == mg->mg_vd->vdev_log_mg,
mc == spa_embedded_log_class(mg->mg_vd->vdev_spa));
mg->mg_histogram[i + ashift] -=
msp->ms_sm->sm_phys->smp_histogram[i];
@ -2741,14 +2759,25 @@ metaslab_fini(metaslab_t *msp)
mutex_enter(&msp->ms_lock);
VERIFY(msp->ms_group == NULL);
/*
* If the range trees haven't been allocated, this metaslab hasn't
* been through metaslab_sync_done() for the first time yet, so its
* space hasn't been accounted for in its vdev and doesn't need to be
* subtracted.
*/
if (msp->ms_freed != NULL) {
metaslab_space_update(vd, mg->mg_class,
-metaslab_allocated_space(msp), 0, -msp->ms_size);
}
space_map_close(msp->ms_sm);
msp->ms_sm = NULL;
metaslab_unload(msp);
range_tree_destroy(msp->ms_allocatable);
if (msp->ms_freed != NULL) {
range_tree_destroy(msp->ms_freeing);
range_tree_destroy(msp->ms_freed);
@ -2758,20 +2787,19 @@ metaslab_fini(metaslab_t *msp)
metaslab_unflushed_changes_memused(msp);
range_tree_vacate(msp->ms_unflushed_allocs, NULL, NULL);
range_tree_destroy(msp->ms_unflushed_allocs);
range_tree_destroy(msp->ms_checkpointing);
range_tree_vacate(msp->ms_unflushed_frees, NULL, NULL);
range_tree_destroy(msp->ms_unflushed_frees);
for (int t = 0; t < TXG_SIZE; t++) {
range_tree_destroy(msp->ms_allocating[t]);
}
for (int t = 0; t < TXG_DEFER_SIZE; t++) {
range_tree_destroy(msp->ms_defer[t]);
}
}
ASSERT0(msp->ms_deferspace);
range_tree_destroy(msp->ms_checkpointing);
for (int t = 0; t < TXG_SIZE; t++)
ASSERT(!txg_list_member(&vd->vdev_ms_list, msp, t));
@ -5113,7 +5141,7 @@ metaslab_alloc_dva(spa_t *spa, metaslab_class_t *mc, uint64_t psize,
* all else fails.
*/
if (vd != NULL && vd->vdev_mg != NULL) {
mg = vd->vdev_mg;
mg = vdev_get_mg(vd, mc);
if (flags & METASLAB_HINTBP_AVOID &&
mg->mg_next != NULL)

28
module/zfs/spa.c
View File

@ -303,10 +303,12 @@ spa_prop_get_config(spa_t *spa, nvlist_t **nvp)
alloc = metaslab_class_get_alloc(mc);
alloc += metaslab_class_get_alloc(spa_special_class(spa));
alloc += metaslab_class_get_alloc(spa_dedup_class(spa));
alloc += metaslab_class_get_alloc(spa_embedded_log_class(spa));
size = metaslab_class_get_space(mc);
size += metaslab_class_get_space(spa_special_class(spa));
size += metaslab_class_get_space(spa_dedup_class(spa));
size += metaslab_class_get_space(spa_embedded_log_class(spa));
spa_prop_add_list(*nvp, ZPOOL_PROP_NAME, spa_name(spa), 0, src);
spa_prop_add_list(*nvp, ZPOOL_PROP_SIZE, NULL, size, src);
@ -1196,6 +1198,8 @@ spa_activate(spa_t *spa, spa_mode_t mode)
spa->spa_normal_class = metaslab_class_create(spa, zfs_metaslab_ops);
spa->spa_log_class = metaslab_class_create(spa, zfs_metaslab_ops);
spa->spa_embedded_log_class =
metaslab_class_create(spa, zfs_metaslab_ops);
spa->spa_special_class = metaslab_class_create(spa, zfs_metaslab_ops);
spa->spa_dedup_class = metaslab_class_create(spa, zfs_metaslab_ops);
@ -1347,6 +1351,9 @@ spa_deactivate(spa_t *spa)
metaslab_class_destroy(spa->spa_log_class);
spa->spa_log_class = NULL;
metaslab_class_destroy(spa->spa_embedded_log_class);
spa->spa_embedded_log_class = NULL;
metaslab_class_destroy(spa->spa_special_class);
spa->spa_special_class = NULL;
@ -2103,6 +2110,9 @@ spa_check_logs(spa_t *spa)
return (rv);
}
/*
* Passivate any log vdevs (note, does not apply to embedded log metaslabs).
*/
static boolean_t
spa_passivate_log(spa_t *spa)
{
@ -2113,10 +2123,10 @@ spa_passivate_log(spa_t *spa)
for (int c = 0; c < rvd->vdev_children; c++) {
vdev_t *tvd = rvd->vdev_child[c];
metaslab_group_t *mg = tvd->vdev_mg;
if (tvd->vdev_islog) {
metaslab_group_passivate(mg);
ASSERT3P(tvd->vdev_log_mg, ==, NULL);
metaslab_group_passivate(tvd->vdev_mg);
slog_found = B_TRUE;
}
}
@ -2124,6 +2134,9 @@ spa_passivate_log(spa_t *spa)
return (slog_found);
}
/*
* Activate any log vdevs (note, does not apply to embedded log metaslabs).
*/
static void
spa_activate_log(spa_t *spa)
{
@ -2133,10 +2146,11 @@ spa_activate_log(spa_t *spa)
for (int c = 0; c < rvd->vdev_children; c++) {
vdev_t *tvd = rvd->vdev_child[c];
metaslab_group_t *mg = tvd->vdev_mg;
if (tvd->vdev_islog)
metaslab_group_activate(mg);
if (tvd->vdev_islog) {
ASSERT3P(tvd->vdev_log_mg, ==, NULL);
metaslab_group_activate(tvd->vdev_mg);
}
}
}
@ -8033,12 +8047,16 @@ spa_async_thread(void *arg)
old_space = metaslab_class_get_space(spa_normal_class(spa));
old_space += metaslab_class_get_space(spa_special_class(spa));
old_space += metaslab_class_get_space(spa_dedup_class(spa));
old_space += metaslab_class_get_space(
spa_embedded_log_class(spa));
spa_config_update(spa, SPA_CONFIG_UPDATE_POOL);
new_space = metaslab_class_get_space(spa_normal_class(spa));
new_space += metaslab_class_get_space(spa_special_class(spa));
new_space += metaslab_class_get_space(spa_dedup_class(spa));
new_space += metaslab_class_get_space(
spa_embedded_log_class(spa));
mutex_exit(&spa_namespace_lock);
/*

59
module/zfs/spa_misc.c
View File

@ -349,9 +349,11 @@ int spa_asize_inflation = 24;
* Normally, we don't allow the last 3.2% (1/(2^spa_slop_shift)) of space in
* the pool to be consumed. This ensures that we don't run the pool
* completely out of space, due to unaccounted changes (e.g. to the MOS).
* It also limits the worst-case time to allocate space. If we have
* less than this amount of free space, most ZPL operations (e.g. write,
* create) will return ENOSPC.
* It also limits the worst-case time to allocate space. If we have less than
* this amount of free space, most ZPL operations (e.g. write, create) will
* return ENOSPC. The ZIL metaslabs (spa_embedded_log_class) are also part of
* this 3.2% of space which can't be consumed by normal writes; the slop space
* "proper" (spa_get_slop_space()) is decreased by the embedded log space.
*
* Certain operations (e.g. file removal, most administrative actions) can
* use half the slop space. They will only return ENOSPC if less than half
@ -1236,6 +1238,7 @@ spa_vdev_config_exit(spa_t *spa, vdev_t *vd, uint64_t txg, int error, char *tag)
*/
ASSERT(metaslab_class_validate(spa_normal_class(spa)) == 0);
ASSERT(metaslab_class_validate(spa_log_class(spa)) == 0);
ASSERT(metaslab_class_validate(spa_embedded_log_class(spa)) == 0);
ASSERT(metaslab_class_validate(spa_special_class(spa)) == 0);
ASSERT(metaslab_class_validate(spa_dedup_class(spa)) == 0);
@ -1776,17 +1779,37 @@ spa_get_worst_case_asize(spa_t *spa, uint64_t lsize)
}
/*
* Return the amount of slop space in bytes. It is 1/32 of the pool (3.2%),
* or at least 128MB, unless that would cause it to be more than half the
* pool size.
* Return the amount of slop space in bytes. It is typically 1/32 of the pool
* (3.2%), minus the embedded log space. On very small pools, it may be
* slightly larger than this. The embedded log space is not included in
* spa_dspace. By subtracting it, the usable space (per "zfs list") is a
* constant 97% of the total space, regardless of metaslab size (assuming the
* default spa_slop_shift=5 and a non-tiny pool).
*
* See the comment above spa_slop_shift for details.
* See the comment above spa_slop_shift for more details.
*/
uint64_t
spa_get_slop_space(spa_t *spa)
{
uint64_t space = spa_get_dspace(spa);
return (MAX(space >> spa_slop_shift, MIN(space >> 1, spa_min_slop)));
uint64_t slop = space >> spa_slop_shift;
/*
* Subtract the embedded log space, but no more than half the (3.2%)
* unusable space. Note, the "no more than half" is only relevant if
* zfs_embedded_slog_min_ms >> spa_slop_shift < 2, which is not true by
* default.
*/
uint64_t embedded_log =
metaslab_class_get_dspace(spa_embedded_log_class(spa));
slop -= MIN(embedded_log, slop >> 1);
/*
* Slop space should be at least spa_min_slop, but no more than half
* the entire pool.
*/
slop = MAX(slop, MIN(space >> 1, spa_min_slop));
return (slop);
}
uint64_t
@ -1872,6 +1895,12 @@ spa_log_class(spa_t *spa)
return (spa->spa_log_class);
}
metaslab_class_t *
spa_embedded_log_class(spa_t *spa)
{
return (spa->spa_embedded_log_class);
}
metaslab_class_t *
spa_special_class(spa_t *spa)
{
@ -1891,12 +1920,10 @@ metaslab_class_t *
spa_preferred_class(spa_t *spa, uint64_t size, dmu_object_type_t objtype,
uint_t level, uint_t special_smallblk)
{
if (DMU_OT_IS_ZIL(objtype)) {
if (spa->spa_log_class->mc_groups != 0)
return (spa_log_class(spa));
else
return (spa_normal_class(spa));
}
/*
* ZIL allocations determine their class in zio_alloc_zil().
*/
ASSERT(objtype != DMU_OT_INTENT_LOG);
boolean_t has_special_class = spa->spa_special_class->mc_groups != 0;
@ -2432,9 +2459,9 @@ spa_fini(void)
}
/*
* Return whether this pool has slogs. No locking needed.
* Return whether this pool has a dedicated slog device. No locking needed.
* It's not a problem if the wrong answer is returned as it's only for
* performance and not correctness
* performance and not correctness.
*/
boolean_t
spa_has_slogs(spa_t *spa)

144
module/zfs/vdev.c
View File

@ -59,6 +59,27 @@
#include <sys/zvol.h>
#include <sys/zfs_ratelimit.h>
/*
* One metaslab from each (normal-class) vdev is used by the ZIL. These are
* called "embedded slog metaslabs", are referenced by vdev_log_mg, and are
* part of the spa_embedded_log_class. The metaslab with the most free space
* in each vdev is selected for this purpose when the pool is opened (or a
* vdev is added). See vdev_metaslab_init().
*
* Log blocks can be allocated from the following locations. Each one is tried
* in order until the allocation succeeds:
* 1. dedicated log vdevs, aka "slog" (spa_log_class)
* 2. embedded slog metaslabs (spa_embedded_log_class)
* 3. other metaslabs in normal vdevs (spa_normal_class)
*
* zfs_embedded_slog_min_ms disables the embedded slog if there are fewer
* than this number of metaslabs in the vdev. This ensures that we don't set
* aside an unreasonable amount of space for the ZIL. If set to less than
* 1 << (spa_slop_shift + 1), on small pools the usable space may be reduced
* (by more than 1<<spa_slop_shift) due to the embedded slog metaslab.
*/
int zfs_embedded_slog_min_ms = 64;
/* default target for number of metaslabs per top-level vdev */
int zfs_vdev_default_ms_count = 200;
@ -223,6 +244,22 @@ vdev_getops(const char *type)
return (ops);
}
/*
* Given a vdev and a metaslab class, find which metaslab group we're
* interested in. All vdevs may belong to two different metaslab classes.
* Dedicated slog devices use only the primary metaslab group, rather than a
* separate log group. For embedded slogs, the vdev_log_mg will be non-NULL.
*/
metaslab_group_t *
vdev_get_mg(vdev_t *vd, metaslab_class_t *mc)
{
if (mc == spa_embedded_log_class(vd->vdev_spa) &&
vd->vdev_log_mg != NULL)
return (vd->vdev_log_mg);
else
return (vd->vdev_mg);
}
/* ARGSUSED */
void
vdev_default_xlate(vdev_t *vd, const range_seg64_t *logical_rs,
@ -978,6 +1015,11 @@ vdev_free(vdev_t *vd)
metaslab_group_destroy(vd->vdev_mg);
vd->vdev_mg = NULL;
}
if (vd->vdev_log_mg != NULL) {
ASSERT0(vd->vdev_ms_count);
metaslab_group_destroy(vd->vdev_log_mg);
vd->vdev_log_mg = NULL;
}
ASSERT0(vd->vdev_stat.vs_space);
ASSERT0(vd->vdev_stat.vs_dspace);
@ -1098,14 +1140,20 @@ vdev_top_transfer(vdev_t *svd, vdev_t *tvd)
if (tvd->vdev_mg)
ASSERT3P(tvd->vdev_mg, ==, svd->vdev_mg);
if (tvd->vdev_log_mg)
ASSERT3P(tvd->vdev_log_mg, ==, svd->vdev_log_mg);
tvd->vdev_mg = svd->vdev_mg;
tvd->vdev_log_mg = svd->vdev_log_mg;
tvd->vdev_ms = svd->vdev_ms;
svd->vdev_mg = NULL;
svd->vdev_log_mg = NULL;
svd->vdev_ms = NULL;
if (tvd->vdev_mg != NULL)
tvd->vdev_mg->mg_vd = tvd;
if (tvd->vdev_log_mg != NULL)
tvd->vdev_log_mg->mg_vd = tvd;
tvd->vdev_checkpoint_sm = svd->vdev_checkpoint_sm;
svd->vdev_checkpoint_sm = NULL;
@ -1283,7 +1331,7 @@ vdev_remove_parent(vdev_t *cvd)
vdev_free(mvd);
}
static void
void
vdev_metaslab_group_create(vdev_t *vd)
{
spa_t *spa = vd->vdev_spa;
@ -1317,6 +1365,11 @@ vdev_metaslab_group_create(vdev_t *vd)
vd->vdev_mg = metaslab_group_create(mc, vd,
spa->spa_alloc_count);
if (!vd->vdev_islog) {
vd->vdev_log_mg = metaslab_group_create(
spa_embedded_log_class(spa), vd, 1);
}
/*
* The spa ashift min/max only apply for the normal metaslab
* class. Class destination is late binding so ashift boundry
@ -1340,8 +1393,6 @@ int
vdev_metaslab_init(vdev_t *vd, uint64_t txg)
{
spa_t *spa = vd->vdev_spa;
objset_t *mos = spa->spa_meta_objset;
uint64_t m;
uint64_t oldc = vd->vdev_ms_count;
uint64_t newc = vd->vdev_asize >> vd->vdev_ms_shift;
metaslab_t **mspp;
@ -1369,16 +1420,17 @@ vdev_metaslab_init(vdev_t *vd, uint64_t txg)
vd->vdev_ms = mspp;
vd->vdev_ms_count = newc;
for (m = oldc; m < newc; m++) {
uint64_t object = 0;
for (uint64_t m = oldc; m < newc; m++) {
uint64_t object = 0;
/*
* vdev_ms_array may be 0 if we are creating the "fake"
* metaslabs for an indirect vdev for zdb's leak detection.
* See zdb_leak_init().
*/
if (txg == 0 && vd->vdev_ms_array != 0) {
error = dmu_read(mos, vd->vdev_ms_array,
error = dmu_read(spa->spa_meta_objset,
vd->vdev_ms_array,
m * sizeof (uint64_t), sizeof (uint64_t), &object,
DMU_READ_PREFETCH);
if (error != 0) {
@ -1388,17 +1440,6 @@ vdev_metaslab_init(vdev_t *vd, uint64_t txg)
}
}
#ifndef _KERNEL
/*
* To accommodate zdb_leak_init() fake indirect
* metaslabs, we allocate a metaslab group for
* indirect vdevs which normally don't have one.
*/
if (vd->vdev_mg == NULL) {
ASSERT0(vdev_is_concrete(vd));
vdev_metaslab_group_create(vd);
}
#endif
error = metaslab_init(vd->vdev_mg, m, object, txg,
&(vd->vdev_ms[m]));
if (error != 0) {
@ -1408,6 +1449,47 @@ vdev_metaslab_init(vdev_t *vd, uint64_t txg)
}
}
/*
* Find the emptiest metaslab on the vdev and mark it for use for
* embedded slog by moving it from the regular to the log metaslab
* group.
*/
if (vd->vdev_mg->mg_class == spa_normal_class(spa) &&
vd->vdev_ms_count > zfs_embedded_slog_min_ms &&
avl_is_empty(&vd->vdev_log_mg->mg_metaslab_tree)) {
uint64_t slog_msid = 0;
uint64_t smallest = UINT64_MAX;
/*
* Note, we only search the new metaslabs, because the old
* (pre-existing) ones may be active (e.g. have non-empty
* range_tree's), and we don't move them to the new
* metaslab_t.
*/
for (uint64_t m = oldc; m < newc; m++) {
uint64_t alloc =
space_map_allocated(vd->vdev_ms[m]->ms_sm);
if (alloc < smallest) {
slog_msid = m;
smallest = alloc;
}
}
metaslab_t *slog_ms = vd->vdev_ms[slog_msid];
/*
* The metaslab was marked as dirty at the end of
* metaslab_init(). Remove it from the dirty list so that we
* can uninitialize and reinitialize it to the new class.
*/
if (txg != 0) {
(void) txg_list_remove_this(&vd->vdev_ms_list,
slog_ms, txg);
}
uint64_t sm_obj = space_map_object(slog_ms->ms_sm);
metaslab_fini(slog_ms);
VERIFY0(metaslab_init(vd->vdev_log_mg, slog_msid, sm_obj, txg,
&vd->vdev_ms[slog_msid]));
}
if (txg == 0)
spa_config_enter(spa, SCL_ALLOC, FTAG, RW_WRITER);
@ -1418,6 +1500,8 @@ vdev_metaslab_init(vdev_t *vd, uint64_t txg)
*/
if (!expanding && !vd->vdev_removing) {
metaslab_group_activate(vd->vdev_mg);
if (vd->vdev_log_mg != NULL)
metaslab_group_activate(vd->vdev_log_mg);
}
if (txg == 0)
@ -1453,7 +1537,12 @@ vdev_metaslab_fini(vdev_t *vd)
if (vd->vdev_ms != NULL) {
metaslab_group_t *mg = vd->vdev_mg;
metaslab_group_passivate(mg);
if (vd->vdev_log_mg != NULL) {
ASSERT(!vd->vdev_islog);
metaslab_group_passivate(vd->vdev_log_mg);
}
uint64_t count = vd->vdev_ms_count;
for (uint64_t m = 0; m < count; m++) {
@ -1463,11 +1552,13 @@ vdev_metaslab_fini(vdev_t *vd)
}
vmem_free(vd->vdev_ms, count * sizeof (metaslab_t *));
vd->vdev_ms = NULL;
vd->vdev_ms_count = 0;
for (int i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i++)
for (int i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i++) {
ASSERT0(mg->mg_histogram[i]);
if (vd->vdev_log_mg != NULL)
ASSERT0(vd->vdev_log_mg->mg_histogram[i]);
}
}
ASSERT0(vd->vdev_ms_count);
ASSERT3U(vd->vdev_pending_fastwrite, ==, 0);
@ -3531,8 +3622,11 @@ vdev_sync_done(vdev_t *vd, uint64_t txg)
!= NULL)
metaslab_sync_done(msp, txg);
if (reassess)
if (reassess) {
metaslab_sync_reassess(vd->vdev_mg);
if (vd->vdev_log_mg != NULL)
metaslab_sync_reassess(vd->vdev_log_mg);
}
}
void
@ -3856,6 +3950,7 @@ top:
/*
* Prevent any future allocations.
*/
ASSERT3P(tvd->vdev_log_mg, ==, NULL);
metaslab_group_passivate(mg);
(void) spa_vdev_state_exit(spa, vd, 0);
@ -4256,6 +4351,12 @@ vdev_get_stats_ex(vdev_t *vd, vdev_stat_t *vs, vdev_stat_ex_t *vsx)
*/
if (vd->vdev_aux == NULL && vd == vd->vdev_top &&
vdev_is_concrete(vd)) {
/*
* The vdev fragmentation rating doesn't take into
* account the embedded slog metaslab (vdev_log_mg).
* Since it's only one metaslab, it would have a tiny
* impact on the overall fragmentation.
*/
vs->vs_fragmentation = (vd->vdev_mg != NULL) ?
vd->vdev_mg->mg_fragmentation : 0;
}
@ -5234,6 +5335,9 @@ ZFS_MODULE_PARAM(zfs_vdev, vdev_, validate_skip, INT, ZMOD_RW,
ZFS_MODULE_PARAM(zfs, zfs_, nocacheflush, INT, ZMOD_RW,
"Disable cache flushes");
ZFS_MODULE_PARAM(zfs, zfs_, embedded_slog_min_ms, INT, ZMOD_RW,
"Minimum number of metaslabs required to dedicate one for log blocks");
ZFS_MODULE_PARAM_CALL(zfs_vdev, zfs_vdev_, min_auto_ashift,
param_set_min_auto_ashift, param_get_ulong, ZMOD_RW,
"Minimum ashift used when creating new top-level vdevs");

13
module/zfs/vdev_removal.c
View File

@ -1207,6 +1207,11 @@ vdev_remove_complete(spa_t *spa)
vd->vdev_mg = NULL;
spa_log_sm_set_blocklimit(spa);
}
if (vd->vdev_log_mg != NULL) {
ASSERT0(vd->vdev_ms_count);
metaslab_group_destroy(vd->vdev_log_mg);
vd->vdev_log_mg = NULL;
}
ASSERT0(vd->vdev_stat.vs_space);
ASSERT0(vd->vdev_stat.vs_dspace);
@ -1780,6 +1785,8 @@ spa_vdev_remove_cancel_impl(spa_t *spa)
spa_config_enter(spa, SCL_ALLOC | SCL_VDEV, FTAG, RW_WRITER);
vdev_t *vd = vdev_lookup_top(spa, vdid);
metaslab_group_activate(vd->vdev_mg);
ASSERT(!vd->vdev_islog);
metaslab_group_activate(vd->vdev_log_mg);
spa_config_exit(spa, SCL_ALLOC | SCL_VDEV, FTAG);
}
@ -1858,6 +1865,7 @@ spa_vdev_remove_log(vdev_t *vd, uint64_t *txg)
ASSERT(vd->vdev_islog);
ASSERT(vd == vd->vdev_top);
ASSERT3P(vd->vdev_log_mg, ==, NULL);
ASSERT(MUTEX_HELD(&spa_namespace_lock));
/*
@ -1893,6 +1901,7 @@ spa_vdev_remove_log(vdev_t *vd, uint64_t *txg)
if (error != 0) {
metaslab_group_activate(mg);
ASSERT3P(vd->vdev_log_mg, ==, NULL);
return (error);
}
ASSERT0(vd->vdev_stat.vs_alloc);
@ -2121,6 +2130,8 @@ spa_vdev_remove_top(vdev_t *vd, uint64_t *txg)
*/
metaslab_group_t *mg = vd->vdev_mg;
metaslab_group_passivate(mg);
ASSERT(!vd->vdev_islog);
metaslab_group_passivate(vd->vdev_log_mg);
/*
* Wait for the youngest allocations and frees to sync,
@ -2157,6 +2168,8 @@ spa_vdev_remove_top(vdev_t *vd, uint64_t *txg)
if (error != 0) {
metaslab_group_activate(mg);
ASSERT(!vd->vdev_islog);
metaslab_group_activate(vd->vdev_log_mg);
spa_async_request(spa, SPA_ASYNC_INITIALIZE_RESTART);
spa_async_request(spa, SPA_ASYNC_TRIM_RESTART);
spa_async_request(spa, SPA_ASYNC_AUTOTRIM_RESTART);

65
module/zfs/zio.c
View File

@ -2750,10 +2750,9 @@ zio_write_gang_done(zio_t *zio)
}
static zio_t *
zio_write_gang_block(zio_t *pio)
zio_write_gang_block(zio_t *pio, metaslab_class_t *mc)
{
spa_t *spa = pio->io_spa;
metaslab_class_t *mc = spa_normal_class(spa);
blkptr_t *bp = pio->io_bp;
zio_t *gio = pio->io_gang_leader;
zio_t *zio;
@ -3470,6 +3469,17 @@ zio_dva_allocate(zio_t *zio)
zio->io_metaslab_class = mc;
}
/*
* Try allocating the block in the usual metaslab class.
* If that's full, allocate it in the normal class.
* If that's full, allocate as a gang block,
* and if all are full, the allocation fails (which shouldn't happen).
*
* Note that we do not fall back on embedded slog (ZIL) space, to
* preserve unfragmented slog space, which is critical for decent
* sync write performance. If a log allocation fails, we will fall
* back to spa_sync() which is abysmal for performance.
*/
error = metaslab_alloc(spa, mc, zio->io_size, bp,
zio->io_prop.zp_copies, zio->io_txg, NULL, flags,
&zio->io_alloc_list, zio, zio->io_allocator);
@ -3489,26 +3499,38 @@ zio_dva_allocate(zio_t *zio)
zio->io_prop.zp_copies, zio->io_allocator, zio);
zio->io_flags &= ~ZIO_FLAG_IO_ALLOCATING;
mc = spa_normal_class(spa);
VERIFY(metaslab_class_throttle_reserve(mc,
VERIFY(metaslab_class_throttle_reserve(
spa_normal_class(spa),
zio->io_prop.zp_copies, zio->io_allocator, zio,
flags | METASLAB_MUST_RESERVE));
} else {
mc = spa_normal_class(spa);
}
zio->io_metaslab_class = mc;
zio->io_metaslab_class = mc = spa_normal_class(spa);
if (zfs_flags & ZFS_DEBUG_METASLAB_ALLOC) {
zfs_dbgmsg("%s: metaslab allocation failure, "
"trying normal class: zio %px, size %llu, error %d",
spa_name(spa), zio, zio->io_size, error);
}
error = metaslab_alloc(spa, mc, zio->io_size, bp,
zio->io_prop.zp_copies, zio->io_txg, NULL, flags,
&zio->io_alloc_list, zio, zio->io_allocator);
}
if (error == ENOSPC && zio->io_size > SPA_MINBLOCKSIZE) {
if (zfs_flags & ZFS_DEBUG_METASLAB_ALLOC) {
zfs_dbgmsg("%s: metaslab allocation failure, "
"trying ganging: zio %px, size %llu, error %d",
spa_name(spa), zio, zio->io_size, error);
}
return (zio_write_gang_block(zio, mc));
}
if (error != 0) {
if (error != ENOSPC ||
(zfs_flags & ZFS_DEBUG_METASLAB_ALLOC)) {
zfs_dbgmsg("%s: metaslab allocation failure: zio %px, "
"size %llu, error %d", spa_name(spa), zio, zio->io_size,
error);
if (error == ENOSPC && zio->io_size > SPA_MINBLOCKSIZE)
return (zio_write_gang_block(zio));
"size %llu, error %d",
spa_name(spa), zio, zio->io_size, error);
}
zio->io_error = error;
}
@ -3588,15 +3610,18 @@ zio_alloc_zil(spa_t *spa, objset_t *os, uint64_t txg, blkptr_t *new_bp,
int flags = METASLAB_FASTWRITE | METASLAB_ZIL;
int allocator = cityhash4(0, 0, 0, os->os_dsl_dataset->ds_object) %
spa->spa_alloc_count;
error = metaslab_alloc(spa, spa_log_class(spa), size, new_bp,
1, txg, NULL, flags, &io_alloc_list, NULL, allocator);
if (error == 0) {
*slog = TRUE;
} else {
error = metaslab_alloc(spa, spa_normal_class(spa), size, new_bp,
1, txg, NULL, flags, &io_alloc_list, NULL, allocator);
if (error == 0)
*slog = FALSE;
error = metaslab_alloc(spa, spa_log_class(spa), size, new_bp, 1,
txg, NULL, flags, &io_alloc_list, NULL, allocator);
*slog = (error == 0);
if (error != 0) {
error = metaslab_alloc(spa, spa_embedded_log_class(spa), size,
new_bp, 1, txg, NULL, flags,
&io_alloc_list, NULL, allocator);
}
if (error != 0) {
error = metaslab_alloc(spa, spa_normal_class(spa), size,
new_bp, 1, txg, NULL, flags,
&io_alloc_list, NULL, allocator);
}
metaslab_trace_fini(&io_alloc_list);