linux-kernel - perf stat output

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Message-ID: <193b0f820911121403w35c57158kf3721309e1f2ebd7@mail.gmail.com>
Date:	Thu, 12 Nov 2009 20:03:11 -0200
From:	Lucas De Marchi <lucas.de.marchi@...il.com>
To:	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: perf stat output

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?

The last question: what does the  "scaled from X%" mean? Is it related
to the maximum number of performance registers a processor can count
at a time?


Thanks

Lucas De Marchi
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