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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
Download patch file Download diff file Expand all files Collapse all files

17
include/linux/lockdep.h
View file

@ -130,12 +130,24 @@ struct lock_time {
unsigned long nr;
};
enum bounce_type {
bounce_acquired_write,
bounce_acquired_read,
bounce_contended_write,
bounce_contended_read,
nr_bounce_types,
bounce_acquired = bounce_acquired_write,
bounce_contended = bounce_contended_write,
};
struct lock_class_stats {
unsigned long contention_point[4];
struct lock_time read_waittime;
struct lock_time write_waittime;
struct lock_time read_holdtime;
struct lock_time write_holdtime;
unsigned long bounces[nr_bounce_types];
};
struct lock_class_stats lock_stats(struct lock_class *class);
@ -150,6 +162,9 @@ struct lockdep_map {
struct lock_class_key *key;
struct lock_class *class_cache;
const char *name;
#ifdef CONFIG_LOCK_STAT
int cpu;
#endif
};
/*
@ -321,8 +336,8 @@ do { \
if (!try(_lock)) { \
lock_contended(&(_lock)->dep_map, _RET_IP_); \
lock(_lock); \
lock_acquired(&(_lock)->dep_map); \
} \
lock_acquired(&(_lock)->dep_map); \
} while (0)
#else /* CONFIG_LOCK_STAT */