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Reduce dp_lock scope for MOS writes

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dp_mos_*_delta fields have no relation to other things protected
by dp_lock.  Plus as write-mostly/read-once they are perfect
candidates for wmsums.  Their conversion into such significantly
reduces dp_lock contention when writing lots of DDT/BRT blocks.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Alexander Motin <[email protected]>
Closes #18858
This commit is contained in:
Alexander Motin authored and GitHub committed 2026-07-31 09:29:18 -07:00
1 parent 023d44b9ef
commit 596c7a0ecb
2 files changed
+24 -16
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include/sys/dsl_pool.h
+5 -3
View File
@@ -42,6 +42,7 @@
#include <sys/dsl_synctask.h>
#include <sys/mmp.h>
#include <sys/aggsum.h>
#include <sys/wmsum.h>
#ifdef __cplusplus
extern "C" {
@@ -118,13 +119,14 @@ typedef struct dsl_pool {
uint64_t dp_dirty_pertxg[TXG_SIZE];
uint64_t dp_dirty_total;
uint64_t dp_long_free_dirty_pertxg[TXG_SIZE];
uint64_t dp_mos_used_delta;
uint64_t dp_mos_compressed_delta;
uint64_t dp_mos_uncompressed_delta;
aggsum_t dp_wrlog_pertxg[TXG_SIZE];
aggsum_t dp_wrlog_total;
wmsum_t dp_mos_used_delta;
wmsum_t dp_mos_compressed_delta;
wmsum_t dp_mos_uncompressed_delta;
/*
* Time of most recently scheduled (furthest in the future)
* wakeup for delayed transactions.
module/zfs/dsl_pool.c
+19 -13
View File
@@ -226,6 +226,10 @@ dsl_pool_open_impl(spa_t *spa, uint64_t txg)
aggsum_init(&dp->dp_wrlog_pertxg[i], 0);
}
wmsum_init(&dp->dp_mos_used_delta, 0);
wmsum_init(&dp->dp_mos_compressed_delta, 0);
wmsum_init(&dp->dp_mos_uncompressed_delta, 0);
dp->dp_zrele_taskq = taskq_create("z_zrele", 100, defclsyspri,
boot_ncpus * 8, INT_MAX, TASKQ_PREPOPULATE | TASKQ_DYNAMIC |
TASKQ_THREADS_CPU_PCT);
@@ -437,6 +441,10 @@ dsl_pool_close(dsl_pool_t *dp)
aggsum_fini(&dp->dp_wrlog_pertxg[i]);
}
wmsum_fini(&dp->dp_mos_used_delta);
wmsum_fini(&dp->dp_mos_compressed_delta);
wmsum_fini(&dp->dp_mos_uncompressed_delta);
taskq_destroy(dp->dp_unlinked_drain_taskq);
taskq_destroy(dp->dp_zrele_taskq);
if (dp->dp_blkstats != NULL)
@@ -572,11 +580,9 @@ dsl_pool_mos_diduse_space(dsl_pool_t *dp,
int64_t used, int64_t comp, int64_t uncomp)
{
ASSERT3U(comp, ==, uncomp); /* it's all metadata */
mutex_enter(&dp->dp_lock);
dp->dp_mos_used_delta += used;
dp->dp_mos_compressed_delta += comp;
dp->dp_mos_uncompressed_delta += uncomp;
mutex_exit(&dp->dp_lock);
wmsum_add(&dp->dp_mos_used_delta, used);
wmsum_add(&dp->dp_mos_compressed_delta, comp);
wmsum_add(&dp->dp_mos_uncompressed_delta, uncomp);
}
static void
@@ -803,15 +809,15 @@ dsl_pool_sync(dsl_pool_t *dp, uint64_t txg)
* (dp_mos_dir). We can't modify the mos while we're syncing
* it, so we remember the deltas and apply them here.
*/
if (dp->dp_mos_used_delta != 0 || dp->dp_mos_compressed_delta != 0 ||
dp->dp_mos_uncompressed_delta != 0) {
int64_t mos_used = wmsum_value(&dp->dp_mos_used_delta);
int64_t mos_comp = wmsum_value(&dp->dp_mos_compressed_delta);
int64_t mos_uncomp = wmsum_value(&dp->dp_mos_uncompressed_delta);
if (mos_used != 0 || mos_comp != 0 || mos_uncomp != 0) {
dsl_dir_diduse_space(dp->dp_mos_dir, DD_USED_HEAD,
dp->dp_mos_used_delta,
dp->dp_mos_compressed_delta,
dp->dp_mos_uncompressed_delta, tx);
dp->dp_mos_used_delta = 0;
dp->dp_mos_compressed_delta = 0;
dp->dp_mos_uncompressed_delta = 0;
mos_used, mos_comp, mos_uncomp, tx);
wmsum_add(&dp->dp_mos_used_delta, -mos_used);
wmsum_add(&dp->dp_mos_compressed_delta, -mos_comp);
wmsum_add(&dp->dp_mos_uncompressed_delta, -mos_uncomp);
}
if (dmu_objset_is_dirty(mos, txg)) {