lockstat: measure lock bouncing

    __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>

1 files changed, 16 insertions, 1 deletions

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 3d3386b88b6a..0e843bf65877 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -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 */