diff options
| author | Alexander Motin <[email protected]> | 2023-10-20 15:37:16 -0400 |
|---|---|---|
| committer | GitHub <[email protected]> | 2023-10-20 12:37:16 -0700 |
| commit | 4fbc52495552b7e8b3337c94d0b7080db65657b8 (patch) | |
| tree | d0b2ccca968b7bd1b82022b456b5b330fa8b9190 | |
| parent | de7b1ae30ab83c37978902dfd53c1ac783ddbc6e (diff) | |
Remove lock from dsl_pool_need_dirty_delay()
Torn reads/writes of dp_dirty_total are unlikely: on 64-bit systems
due to register size, while on 32-bit due to memory constraints.
And even if we hit some race, the code implementing the delay takes
the lock any way.
Removal of the poll-wide lock acquisition saves ~1% of CPU time on
8-thread 8KB write workload.
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Alexander Motin <[email protected]>
Sponsored by: iXsystems, Inc.
Closes #15390
| -rw-r--r-- | module/zfs/dsl_pool.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/module/zfs/dsl_pool.c b/module/zfs/dsl_pool.c index 9120fef93..17b971248 100644 --- a/module/zfs/dsl_pool.c +++ b/module/zfs/dsl_pool.c @@ -965,18 +965,18 @@ dsl_pool_need_dirty_delay(dsl_pool_t *dp) uint64_t delay_min_bytes = zfs_dirty_data_max * zfs_delay_min_dirty_percent / 100; - mutex_enter(&dp->dp_lock); - uint64_t dirty = dp->dp_dirty_total; - mutex_exit(&dp->dp_lock); - - return (dirty > delay_min_bytes); + /* + * We are not taking the dp_lock here and few other places, since torn + * reads are unlikely: on 64-bit systems due to register size and on + * 32-bit due to memory constraints. Pool-wide locks in hot path may + * be too expensive, while we do not need a precise result here. + */ + return (dp->dp_dirty_total > delay_min_bytes); } static boolean_t dsl_pool_need_dirty_sync(dsl_pool_t *dp, uint64_t txg) { - ASSERT(MUTEX_HELD(&dp->dp_lock)); - uint64_t dirty_min_bytes = zfs_dirty_data_max * zfs_dirty_data_sync_percent / 100; uint64_t dirty = dp->dp_dirty_pertxg[txg & TXG_MASK]; |