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perf(lock): shared locker latch on lock-get hot path (2.7x at 24t) #28

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Merged
gburd merged 1 commit into from
Jun 20, 2026
+12 −2
Merged

perf(lock): shared locker latch on lock-get hot path (2.7x at 24t) #28

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2 changes: 2 additions & 0 deletions src/dbinc/lock.h
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Original file line number Diff line number Diff line change
Expand Up @@ -329,6 +329,8 @@ struct __db_lock { /* SHARED */
MUTEX_UNLOCK(env, (region)->mtx_dd)
#define LOCK_LOCKERS(env, region) \
MUTEX_LOCK(env, (region)->mtx_lockers)
#define RDLOCK_LOCKERS(env, region) \
MUTEX_READLOCK(env, (region)->mtx_lockers)
#define UNLOCK_LOCKERS(env, region) \
MUTEX_UNLOCK(env, (region)->mtx_lockers)

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2 changes: 1 addition & 1 deletion src/lock/lock.c
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Original file line number Diff line number Diff line change
Expand Up @@ -596,7 +596,7 @@ __lock_get_api(env, locker, flags, obj, lock_mode, lock)

region = env->lk_handle->reginfo.primary;

LOCK_LOCKERS(env, region);
RDLOCK_LOCKERS(env, region);
ret = __lock_getlocker_int(env->lk_handle, locker, 0, &sh_locker);
UNLOCK_LOCKERS(env, region);
LOCK_SYSTEM_LOCK(env->lk_handle, region);
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10 changes: 9 additions & 1 deletion src/lock/lock_region.c
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Original file line number Diff line number Diff line change
Expand Up @@ -253,8 +253,16 @@ __lock_region_init(env, lt)
env, MTX_LOCK_REGION, 0, &region->mtx_dd)) != 0)
return (ret);

/*
* The locker mutex is a SHARED latch: the hot lock-get path looks up
* an existing locker (a read-only hash walk) and takes it shared, so
* many cores can resolve their locker concurrently; locker create,
* free, the deadlock detector's locker-list walk, failchk, and stat
* take it exclusive. This removes the per-operation global
* serialization on lock_get/lock_put.
*/
if ((ret = __mutex_alloc(
env, MTX_LOCK_REGION, 0, &region->mtx_lockers)) != 0)
env, MTX_LOCK_REGION, DB_MUTEX_SHARED, &region->mtx_lockers)) != 0)
return (ret);

/* Allocate room for the locker hash table and initialize it. */
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