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, 12 insertions, 7 deletions

diff --git a/kernel/lockdep_proc.c b/kernel/lockdep_proc.c
index 39163ed1bf0a..7ff80135cbeb 100644
--- a/kernel/lockdep_proc.c
+++ b/kernel/lockdep_proc.c
@@ -430,16 +430,18 @@ static void seq_stats(struct seq_file *m, struct lock_stat_data *data)
                 else
                         seq_printf(m, "%40s:", name);
 
+                seq_printf(m, "%14lu ", stats->bounces[bounce_contended_write]);
                 seq_lock_time(m, &stats->write_waittime);
-                seq_puts(m, " ");
+                seq_printf(m, " %14lu ", stats->bounces[bounce_acquired_write]);
                 seq_lock_time(m, &stats->write_holdtime);
                 seq_puts(m, "\n");
         }
 
         if (stats->read_holdtime.nr) {
                 seq_printf(m, "%38s-R:", name);
+                seq_printf(m, "%14lu ", stats->bounces[bounce_contended_read]);
                 seq_lock_time(m, &stats->read_waittime);
-                seq_puts(m, " ");
+                seq_printf(m, " %14lu ", stats->bounces[bounce_acquired_read]);
                 seq_lock_time(m, &stats->read_holdtime);
                 seq_puts(m, "\n");
         }
@@ -469,26 +471,29 @@ static void seq_stats(struct seq_file *m, struct lock_stat_data *data)
         }
         if (i) {
                 seq_puts(m, "\n");
-                seq_line(m, '.', 0, 40 + 1 + 8 * (14 + 1));
+                seq_line(m, '.', 0, 40 + 1 + 10 * (14 + 1));
                 seq_puts(m, "\n");
         }
 }
 
 static void seq_header(struct seq_file *m)
 {
-        seq_printf(m, "lock_stat version 0.1\n");
-        seq_line(m, '-', 0, 40 + 1 + 8 * (14 + 1));
-        seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s\n",
+        seq_printf(m, "lock_stat version 0.2\n");
+        seq_line(m, '-', 0, 40 + 1 + 10 * (14 + 1));
+        seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s "
+                        "%14s %14s\n",
                         "class name",
+                        "con-bounces",
                         "contentions",
                         "waittime-min",
                         "waittime-max",
                         "waittime-total",
+                        "acq-bounces",
                         "acquisitions",
                         "holdtime-min",
                         "holdtime-max",
                         "holdtime-total");
-        seq_line(m, '-', 0, 40 + 1 + 8 * (14 + 1));
+        seq_line(m, '-', 0, 40 + 1 + 10 * (14 + 1));
         seq_printf(m, "\n");
 }