Date: Fri, 17 Jul 2015 13:25:53 -0700
From: Andi Kleen <ak@linux.intel.com>
To: kan.liang@intel.com
Cc: a.p.zijlstra@chello.nl, mingo@redhat.com, acme@kernel.org,
        eranian@google.com, mark.rutland@arm.com, adrian.hunter@intel.com,
        dsahern@gmail.com, jolsa@kernel.org, namhyung@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 8/9] perf,tools: caculate and save tsc/avg/bzy freq in
 he_stat
Message-ID: <20150717202553.GG7380@tassilo.jf.intel.com>
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 <1437078831-10152-9-git-send-email-kan.liang@intel.com>
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> +	if (sample->read.time_running > 0) {
> +		freq.tsc_freq = (1000 * sample->tsc) / sample->read.time_running;
> +		freq.avg_freq = (1000 * sample->aperf) / sample->read.time_running;
> +		if (sample->aperf > 0)
> +			freq.bzy_freq = freq.tsc_freq * sample->mperf / sample->aperf;

Sorry didn't notice that earlier. The formula is not correct. 
aperf/mperf is not necessarily the frequency, it is essentially a load average
of the CPU. It should be reported as such. Also only the ratio is
architecturally defined.

The right way to compute frequency is cycles / ref-cycles
TSC can be used to accurately compute CPU utilization tsc / ref-cycles

It would be useful to report all three metrics.

-Andi
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