linux-kernel - Re: Perf events warning..

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Message-ID: <CA+55aFwkQUrsG6JFVuL5u_0waLPrYqsgHtKRnMHD-Tz0KivaNQ@mail.gmail.com>
Date:	Tue, 15 May 2012 08:48:38 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-kernel@...r.kernel.org
Subject: Re: Perf events warning..

On Tue, May 15, 2012 at 3:49 AM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
>>
>> It did use "make -j64 test" to make the load a *bit* more interesting
>> (and go noticeably faster), but other than that you got it.
>
> OK, that limits the scope of crazy scenarios I have to consider, still
> no immediate clue though..

Actually, looking into my history, some of them had "-fg", and some of
them used "cycles:p". It looks like I had three different combinations
I used:

 - the one I already mentioned:

        perf record -f -e cycles:pp make -j64 test

 - two variations of the above:

        perf record -fg -e cycles:p make -j64 test
        perf record -fg -e cycles:pp make -j64 test

and I don't know which of these caused the warning.

I did profile some other things too (I commonly do profiles of "git
diff" and "make -j" on a fully built kernel), but they used the same
flags, so from a perf standpoint they shouldn't be all that different.

                     Linus
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