Messages in this thread Patch in this message | | | Date | Wed, 9 Nov 2011 16:07:14 +0800 | From | Yong Zhang <> | Subject | [PATCH 2/2] lockdep: always try to set ->class_cache in register_lock_class() lockdep_init_map() |
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From: Yong Zhang <yong.zhang0@gmail.com>
commit [62016250 lockdep: Add improved subclass caching] try 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 try 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 <yong.zhang0@gmail.com> Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@elte.hu> --- kernel/lockdep.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 21ea1dc..e9cbb99 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) -- 1.7.5.4
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