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authorIngo Molnar <mingo@elte.hu>2007-06-01 03:47:16 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-06-01 11:18:30 -0400
commitc1a834dc704763673df10282995257f2de93cbe9 (patch)
tree66a0bc5ffbf6732eaa5fc6f554c13b235005c4cd /Documentation
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 'Documentation')
-rw-r--r--Documentation/hrtimer/timer_stats.txt7
1 files changed, 4 insertions, 3 deletions
diff --git a/Documentation/hrtimer/timer_stats.txt b/Documentation/hrtimer/timer_stats.txt
index 27f782e3593f..22b0814d0ad0 100644
--- a/Documentation/hrtimer/timer_stats.txt
+++ b/Documentation/hrtimer/timer_stats.txt
@@ -2,9 +2,10 @@ timer_stats - timer usage statistics
2------------------------------------ 2------------------------------------
3 3
4timer_stats is a debugging facility to make the timer (ab)usage in a Linux 4timer_stats is a debugging facility to make the timer (ab)usage in a Linux
5system visible to kernel and userspace developers. It is not intended for 5system visible to kernel and userspace developers. If enabled in the config
6production usage as it adds significant overhead to the (hr)timer code and the 6but not used it has almost zero runtime overhead, and a relatively small
7(hr)timer data structures. 7data structure overhead. Even if collection is enabled runtime all the
8locking is per-CPU and lookup is hashed.
8 9
9timer_stats should be used by kernel and userspace developers to verify that 10timer_stats should be used by kernel and userspace developers to verify that
10their code does not make unduly use of timers. This helps to avoid unnecessary 11their code does not make unduly use of timers. This helps to avoid unnecessary