Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq

Peter Zijlstra
2016-04-01T08:23:26Z

Trim your emails

On Fri, Apr 01, 2016 at 10:16:42AM +0200, Stephane Gasparini wrote:

> > That means these delta's can be arbitrarily large, in fact the MSRs can
> > have wrapped however many times.
>
> 64 bits is 18 446 744 073 709 551 615
>
> so even assuming a 10 GHz frequency if my math are good this is more than
> 58 years before the MSR wrap around, assuming the device ran always at max
> freq.

fair enough.. but going with 10Ghz, cpu_khz would be 10e6 ~ 33 bits,
which effectively reduces the wrap/overflow time to just 31 bits, which
per that frequency is just ~1/4th of a second.