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Groups > linux.kernel > #1369099
| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq |
| Date | 2016-04-01 10:30 +0200 |
| Message-ID | <rj2CS-1CC-5@gated-at.bofh.it> (permalink) |
| References | <riZ2h-7Bo-7@gated-at.bofh.it> <riZ2h-7Bo-5@gated-at.bofh.it> <rj2jv-1v4-5@gated-at.bofh.it> <rj2tc-1yL-15@gated-at.bofh.it> <rj2CS-1CC-7@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Fri, Apr 01, 2016 at 10:23:23AM +0200, Peter Zijlstra wrote: > > 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, I can't do maths this morning; 23 bits > which effectively reduces the wrap/overflow time to just 31 bits, which > per that frequency is just ~1/4th of a second. 41 giving lots more, but a reasonable time to wrap/overflow.
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[PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Len Brown <lenb@kernel.org> - 2016-04-01 06:40 +0200
Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freqy Thomas Gleixner <tglx@linutronix.de> - 2016-04-01 10:00 +0200
Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Peter Zijlstra <peterz@infradead.org> - 2016-04-01 10:10 +0200
Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Stephane Gasparini <stephane.gasparini@linux.intel.com> - 2016-04-01 10:20 +0200
Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Peter Zijlstra <peterz@infradead.org> - 2016-04-01 10:30 +0200
Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Stephane Gasparini <stephane.gasparini@linux.intel.com> - 2016-04-01 11:40 +0200
Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Peter Zijlstra <peterz@infradead.org> - 2016-04-01 11:40 +0200
Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Borislav Petkov <bp@alien8.de> - 2016-04-01 12:00 +0200
Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Len Brown <lenb@kernel.org> - 2016-04-02 07:30 +0200
Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Peter Zijlstra <peterz@infradead.org> - 2016-04-01 10:30 +0200
Re: [PATCH] x86: Calculate MHz using APERF/MPERF for cpuinfo and scaling_cur_freq Peter Zijlstra <peterz@infradead.org> - 2016-04-01 10:20 +0200
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