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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 /Documentation
parent9fcc15ec3c1c287a781a4620e52522b6186f26f6 (diff)
downloadop-kernel-dev-c1a834dc704763673df10282995257f2de93cbe9.zip
op-kernel-dev-c1a834dc704763673df10282995257f2de93cbe9.tar.gz
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 27f782e..22b0814 100644
--- a/Documentation/hrtimer/timer_stats.txt
+++ b/Documentation/hrtimer/timer_stats.txt
@@ -2,9 +2,10 @@ timer_stats - timer usage statistics
------------------------------------
timer_stats is a debugging facility to make the timer (ab)usage in a Linux
-system visible to kernel and userspace developers. It is not intended for
-production usage as it adds significant overhead to the (hr)timer code and the
-(hr)timer data structures.
+system visible to kernel and userspace developers. If enabled in the config
+but not used it has almost zero runtime overhead, and a relatively small
+data structure overhead. Even if collection is enabled runtime all the
+locking is per-CPU and lookup is hashed.
timer_stats should be used by kernel and userspace developers to verify that
their code does not make unduly use of timers. This helps to avoid unnecessary
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