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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Stephane Eranian <eranian@google.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
	Ingo Molnar <mingo@elte.hu>,
	Markus Trippelsdorf <markus@trippelsdorf.de>,
	linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>
Subject: Re: WARNING: at arch/x86/kernel/cpu/perf_event.c:989
Date: Mon, 06 Feb 2012 16:02:48 +0100	[thread overview]
Message-ID: <1328540568.2482.7.camel@laptop> (raw)
In-Reply-To: <CABPqkBSuQCJkmJYbno_qsb=erOOf3uf84sQsSCzoov-6=7r40Q@mail.gmail.com>

On Mon, 2012-02-06 at 15:32 +0100, Stephane Eranian wrote:
> I am wondering why we stop and restart the code in perf_adjust_period()
> when it's called from __perf_event_overflow(). Isn't it supposed to be stopped
> already by the model specific interrupt handler. Looks like we do stop/start,
> just to get the reload aspect of start. Is that right? 

Yes it is in order to deal with the case where an excessively long
period is programmed and we want to force load the new period without
having to wait for the old one to complete.

I hit that case several times with the adaptive code and events that
have very uneven rates.


  reply	other threads:[~2012-02-06 15:02 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-02 21:17 WARNING: at arch/x86/kernel/cpu/perf_event.c:989 Markus Trippelsdorf
2012-02-02 21:32 ` Markus Trippelsdorf
2012-02-02 22:22   ` Stephane Eranian
2012-02-04 13:51     ` Ingo Molnar
2012-02-04 18:09       ` Stephane Eranian
2012-02-06  9:54         ` Stephane Eranian
2012-02-06 10:12           ` Eric Dumazet
2012-02-06 10:40             ` Stephane Eranian
2012-02-06 11:11               ` Eric Dumazet
2012-02-06 14:13                 ` Stephane Eranian
2012-02-06 14:29                   ` Peter Zijlstra
2012-02-06 14:32                     ` Stephane Eranian
2012-02-06 15:02                       ` Peter Zijlstra [this message]
2012-02-06 14:38                   ` Ingo Molnar
2012-02-06 14:41                     ` Stephane Eranian
2012-02-06 15:47                       ` Ingo Molnar
2012-02-06 20:44                         ` Stephane Eranian
2012-02-06 20:58                           ` Peter Zijlstra
2012-02-06 21:25                             ` Stephane Eranian

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