linux-kernel - Re: perf stat output

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Date:	Fri, 13 Nov 2009 12:46:26 -0200
From:	Lucas De Marchi <lucas.de.marchi@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: perf stat output

On Fri, Nov 13, 2009 at 06:07, Peter Zijlstra <peterz@...radead.org> wrote:
> On Thu, 2009-11-12 at 20:03 -0200, Lucas De Marchi wrote:
>> Hi all!
>>
>> Some questions about perf stat output. See example:
>>
>>
>> lucas@...-linux:~/programming/testprograms> perf stat -e
>> L1-dcache-loads -e L1-dcache-load-misses -- make -j
>> gcc test_schedchanges.c -o test_schedchanges
>> gcc -pthread test_taskaff1.c -o test_taskaff1
>> gcc -pthread test_taskaff2.c -o test_taskaff2
>> gcc -pthread test_taskaff3.c -o test_taskaff3
>>
>>  Performance counter stats for 'make -j':
>>
>>        161384667  L1-dcache-loads          #      0.000 M/sec
>>               24853791  L1-dcache-load-misses    #      0.000 M/sec
>>
>>                 0.066893389  seconds time elapsed
>>
>> Why do we have both L1-dcache-loads and  L1-dcache-load-misses with
>> 0.000 M/sec? Also, why do we have 0 M/s when running "perf stat -a -e
>> cache-misses -e cache-references" but values different than 0 when
>> running "perf stat -a" without selecting the events?
>
> No idea, you'd have to look at the code computing this M/sec stuff. I
> think Ingo wrote that, so he might have an idea.

But should it be, for example, L1-dcache-loads / seconds time elapsed,
or does it have another meaning?



Lucas De Marchi
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