Re: [PATCH RFC V2 1/1] x86, perf: Add a freq pmu driver

From	Andy Lutomirski <luto@amacapital.net>
Newsgroups	linux.kernel
Subject	Re: [PATCH RFC V2 1/1] x86, perf: Add a freq pmu driver
Date	2015-07-21 08:10 +0200
Message-ID	<pOyUx-8gm-9@gated-at.bofh.it> (permalink)
References	<pOsm6-7eJ-19@gated-at.bofh.it> <pOwg1-4pd-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon, Jul 20, 2015 at 8:10 PM, Stephane Eranian <eranian@google.com> wrote:
> On Mon, Jul 20, 2015 at 8:49 AM, Kan Liang <kan.liang@intel.com> wrote:
>> From: Andy Lutomirski <luto@kernel.org>
>>
>> This patch adds freq PMU to support time and freq related counters
>> includes TSC, IA32_APERF, IA32_MPERF and IA32_PPERF.
>>
>> The events are exposed in sysfs for use by perf stat and other tools.
>> The files are under /sys/devices/freq/events/
>>
>> These events only support system-wide mode counting.
>>
>> The PMU type (attr->type) is PERF_TYPE_FREQ.
>>
>> Example:
>>
>> To caculate the CPU%
>> CPU_Utilization = CPU_CLK_UNHALTED.REF_TSC / TSC
>>
>> $ perf stat -e '{ref-cycles,freq/tsc/}' -C0 -- taskset -c 0 sleep 1
>> 3164023,,ref-cycles,1048387386,100.00
>> 2410812089,,freq/tsc/,1050022373,100.00
>> The CPU% for sleep is 0.13%.
>>
> This event is system-wide only. Thus, the kernel should return
> an error when you try to use it in per-thread mode. That would
> be more consistent with RAPL and uncore events.

I don't know enough about perf's inner workings to be sure, but can't
perf context switch free-running counters like this?

--Andy
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Re: [PATCH RFC V2 1/1] x86, perf: Add a freq pmu driver Andy Lutomirski <luto@amacapital.net> - 2015-07-21 08:10 +0200
  Re: [PATCH RFC V2 1/1] x86, perf: Add a freq pmu driver Stephane Eranian <eranian@google.com> - 2015-07-21 08:30 +0200
    Re: [PATCH RFC V2 1/1] x86, perf: Add a freq pmu driver Andy Lutomirski <luto@amacapital.net> - 2015-07-21 08:30 +0200

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