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Optimize trylock for high cache contention workloads.

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Resolves: RHEL-141072
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Patsy Griffin 2026-02-06 16:08:23 -05:00 committed by Florian Weimer
parent c7f278779c
commit 3b96603253
1 changed files with 46 additions and 0 deletions
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commit 63716823dbad9482e09972907ae98e9cb00f9b86
Author: Sunil K Pandey <sunil.k.pandey@intel.com>
Date: Tue Dec 9 08:57:44 2025 -0800
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>
Conflicts:
nptl/pthread_mutex_trylock.c
Updated for minor context difference
diff -Nrup a/nptl/pthread_mutex_trylock.c b/nptl/pthread_mutex_trylock.c
--- a/nptl/pthread_mutex_trylock.c 2021-08-01 21:33:43.000000000 -0400
+++ b/nptl/pthread_mutex_trylock.c 2026-02-06 13:29:01.508899356 -0500
@@ -49,7 +49,8 @@ ___pthread_mutex_trylock (pthread_mutex_
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. */
mutex->__data.__owner = id;
@@ -72,7 +73,10 @@ ___pthread_mutex_trylock (pthread_mutex_
/*FALL THROUGH*/
case PTHREAD_MUTEX_ADAPTIVE_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;
/* Record the ownership. */