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lockstat: measure lock bouncing

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__acquire
        |
       lock _____
        |        \
        |    __contended
        |         |
        |        wait
        | _______/
        |/
        |
   __acquired
        |
   __release
        |
     unlock

We measure acquisition and contention bouncing.

This is done by recording a cpu stamp in each lock instance.

Contention bouncing requires the cpu stamp to be set on acquisition. Hence we
move __acquired into the generic path.

__acquired is then used to measure acquisition bouncing by comparing the
current cpu with the old stamp before replacing it.

__contended is used to measure contention bouncing (only useful for preemptable
locks)

[akpm@linux-foundation.org: cleanups]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Peter Zijlstra 2007-07-19 01:49:00 -07:00 • committed by Linus Torvalds
parent 443aef0edd
commit 96645678cd
4 changed files with 55 additions and 21 deletions
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2
kernel/mutex.c
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@ -180,8 +180,8 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass)
spin_lock_mutex(&lock->wait_lock, flags);
}
lock_acquired(&lock->dep_map);
done:
lock_acquired(&lock->dep_map);
/* got the lock - rejoice! */
mutex_remove_waiter(lock, &waiter, task_thread_info(task));
debug_mutex_set_owner(lock, task_thread_info(task));