Messages in this thread | | | Date | Tue, 1 Sep 2015 10:57:03 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH V3] perf: x86: Improve accuracy of perf/sched clock |
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On Tue, Sep 01, 2015 at 11:36:38AM +0300, Adrian Hunter wrote: > On 21/08/15 12:05, Adrian Hunter wrote: > > When TSC is stable perf/sched clock is based on it. > > However the conversion from cycles to nanoseconds > > is not as accurate as it could be. Because > > CYC2NS_SCALE_FACTOR is 10, the accuracy is +/- 1/2048 > > > > The change is to calculate the maximum shift that > > results in a multiplier that is still a 32-bit number. > > For example all frequencies over 1 GHz will have > > a shift of 32, making the accuracy of the conversion > > +/- 1/(2^33). That is achieved by using the > > 'clocks_calc_mult_shift()' function. > > > > Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> > > Ping?
I've queued it. Thanks
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