linux-kernel - Re: Perf events warning..

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Message-ID: <1337078996.27694.26.camel@twins>
Date:	Tue, 15 May 2012 12:49:56 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-kernel@...r.kernel.org
Subject: Re: Perf events warning..

On Mon, 2012-05-14 at 15:25 -0700, Linus Torvalds wrote:
> On Mon, May 14, 2012 at 3:20 PM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> >
> > So far I can't make any of the things I came up stick. You ran something
> > simple like: 'perf record -e cycles:pp -F 20000 make test' ? Or did you
> > do something more interesting?
> 
> It was not much more complex than that.
> 
> 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..

I think I've found a possible race, but I can't make it work with that
workload. I've also let your workload run for 2+ hours in trying to
reproduce, but no luck, it must be a very narrow window indeed.

I'll keep prodding at it..
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