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authorIngo Molnar <mingo@elte.hu>2007-06-01 00:47:16 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-06-01 08:18:30 -0700
commitc1a834dc704763673df10282995257f2de93cbe9 (patch)
tree66a0bc5ffbf6732eaa5fc6f554c13b235005c4cd /kernel/time
parent9fcc15ec3c1c287a781a4620e52522b6186f26f6 (diff)
timer stats: speedups
Make timer-stats have almost zero overhead when enabled in the config but not used. (this way distros can enable it more easily) Also update the documentation about overhead of timer_stats - it was written for the first version which had a global lock and a linear list walk based lookup ;-) Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/timer_stats.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/time/timer_stats.c b/kernel/time/timer_stats.c
index fa3d380ca8c..321693724ad 100644
--- a/kernel/time/timer_stats.c
+++ b/kernel/time/timer_stats.c
@@ -236,10 +236,15 @@ void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
/*
* It doesnt matter which lock we take:
*/
- spinlock_t *lock = &per_cpu(lookup_lock, raw_smp_processor_id());
+ spinlock_t *lock;
struct entry *entry, input;
unsigned long flags;
+ if (likely(!active))
+ return;
+
+ lock = &per_cpu(lookup_lock, raw_smp_processor_id());
+
input.timer = timer;
input.start_func = startf;
input.expire_func = timerf;