From 87cdee71166fa107c5dc8e43060eeefa533c6a3b Mon Sep 17 00:00:00 2001 From: Yong Zhang Date: Wed, 9 Nov 2011 16:07:14 +0800 Subject: [PATCH] lockdep: Always try to set ->class_cache in register_lock_class() lockdep_init_map() Commit ["62016250 lockdep: Add improved subclass caching"] tries to improve performance (expecially to reduce the cost of rq->lock) when using lockdep, but it fails due to lockdep_init_map() in which ->class_cache is cleared. The typical caller is lock_set_subclass(), after that class will not be cached anymore. This patch tries to achive the goal of commit 62016250 by always setting ->class_cache in register_lock_class(). === Score comparison of benchmarks === for i in `seq 1 10`; do ./perf bench -f simple sched messaging; done before: min: 0.604, max: 0.660, avg: 0.622 after: min: 0.414, max: 0.473, avg: 0.427 for i in `seq 1 10`; do ./perf bench -f simple sched messaging -g 40; done before: min: 2.347, max: 2.421, avg: 2.391 after: min: 1.652, max: 1.699, avg: 1.671 Signed-off-by: Yong Zhang Cc: Hitoshi Mitake Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20111109080714.GC8124@zhy Signed-off-by: Ingo Molnar --- kernel/lockdep.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index e69434b070da..103bed8423ff 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -722,7 +722,7 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) class = look_up_lock_class(lock, subclass); if (likely(class)) - return class; + goto out_set_class_cache; /* * Debug-check: all keys must be persistent! @@ -807,6 +807,7 @@ out_unlock_set: graph_unlock(); raw_local_irq_restore(flags); +out_set_class_cache: if (!subclass || force) lock->class_cache[0] = class; else if (subclass < NR_LOCKDEP_CACHING_CLASSES) -- 2.34.1