Messages in this thread | | | Date | Sat, 12 Jun 2010 09:18:47 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 2/2] Use ktime_get() instead of sched_clock() for blkio cgroup stats. |
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* Divyesh Shah <dpshah@google.com> wrote:
> This will take care of the pre-emptive kernel issue and the unbounded > TSC drift problem. We will lose resolution though in some cases.
> - blkg->stats.start_group_wait_time = sched_clock(); > + blkg->stats.start_group_wait_time = ktime_to_ns(ktime_get());
Ugh!
ktime_get() can have insanely high overhead. Peter has added local_clock(), if then you should use that and apply checks to make sure the result isnt negative.
Ingo
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