On Tue, 2014-11-04 at 07:23 +0000, Peter Zijlstra wrote:
> On Tue, Nov 04, 2014 at 12:28:36AM +0000, Pawel Moll wrote:
>
> > +int sysctl_perf_sample_time_clk_id = CLOCK_MONOTONIC;
>
> const ?
Sure (unless we have to change it as mentioned below)
> > /*
> > * perf samples are done in some very critical code paths (NMIs).
> > * If they take too much CPU time, the system can lock up and not
> > @@ -324,7 +326,7 @@ extern __weak const char *perf_pmu_name(void)
> >
> > static inline u64 perf_clock(void)
> > {
> > - return local_clock();
> > + return ktime_get_mono_fast_ns();
> > }
>
> Do we maybe want to make it boot-time switchable back to local_clock for
> people with bad systems and or backwards compat issues?
Very good idea, should have came up with it myself :-)
Does __setup("perf_use_local_clock") sound reasonable? Then we have to
decide whether to hide the sysctl "perf_sample_time_clk_id" (my
preferred option, will see how difficult it is) or just provide an
invalid clock_id (eg. -1) in it.
Cheers!
Pawel
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