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nptl: Optimize trylock for high cache contention workloads (BZ #33704) 

Check lock availability before acquisition to reduce cache line
bouncing.  Significantly improves trylock throughput on multi-core
systems under heavy contention.

Tested on x86_64.

Fixes BZ #33704.

Co-authored-by: Alex M Wells <alex.m.wells@intel.com>
Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>
(cherry picked from commit 63716823db)
This commit is contained in:
Sunil K Pandey 2025-12-09 08:57:44 -08:00
parent a965fb342e
commit 7b8f497fe4
1 changed files with 6 additions and 2 deletions
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8
nptl/pthread_mutex_trylock.c
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@ -48,7 +48,8 @@ ___pthread_mutex_trylock (pthread_mutex_t *mutex)
return 0; return 0;
} }
if (lll_trylock (mutex->__data.__lock) == 0) if (atomic_load_relaxed (&(mutex->__data.__lock)) == 0
&& lll_trylock (mutex->__data.__lock) == 0)
{ {
/* Record the ownership. */ /* Record the ownership. */
mutex->__data.__owner = id; mutex->__data.__owner = id;
@ -71,7 +72,10 @@ ___pthread_mutex_trylock (pthread_mutex_t *mutex)
/*FALL THROUGH*/ /*FALL THROUGH*/
case PTHREAD_MUTEX_ADAPTIVE_NP: case PTHREAD_MUTEX_ADAPTIVE_NP:
case PTHREAD_MUTEX_ERRORCHECK_NP: case PTHREAD_MUTEX_ERRORCHECK_NP:
if (lll_trylock (mutex->__data.__lock) != 0) /* Mutex type is already loaded, lock check overhead should
be minimal. */
if (atomic_load_relaxed (&(mutex->__data.__lock)) != 0
|| lll_trylock (mutex->__data.__lock) != 0)
break; break;
/* Record the ownership. */ /* Record the ownership. */