Re: [PATCH v3 1/3] perf: Use monotonic clock as a source for timestamps

[Peter Zijlstra]

On Tue, Nov 04, 2014 at 12:28:36AM +0000, Pawel Moll wrote:

> +int sysctl_perf_sample_time_clk_id = CLOCK_MONOTONIC;

const ?

>  /*
>   * 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?

Everybody using Core2 and older will very much not want to have this
unless they've got a very good reason for wanting it.
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