linux-kernel - Re: [PATCH] perf, powerpc: Fix power_pmu_event

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Message-ID: <1287489030.1994.8.camel@twins>
Date:	Tue, 19 Oct 2010 13:50:30 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Paul Mackerras <paulus@...ba.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org,
	Alexey Kardashevskiy <aik@....ibm.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] perf, powerpc: Fix power_pmu_event_init to not use
 event->ctx

On Tue, 2010-10-19 at 10:28 +0200, Peter Zijlstra wrote:
 
> > (The reason it needs to know whether it is a per-task event is because
> > there are some hardware events on Power systems which only count when
> > the processor is not idle, and there are some fixed-function counters
> > which count such events.  For example, the "run cycles" event counts
> > cycles when the processor is not idle.  If the user asks to count
> > cycles, we can use "run cycles" if this is a per-task event, since the
> > processor is running when the task is running, by definition.  We
> > can't use "run cycles" if the user asks for "cycles" on a system-wide
> > counter.)

Right, so the problem comes from you using run-cycles as cycles? How
does that interact with things like cpu_relax() will that generate a
difference in run-cycles vs cycles?


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