linux-kernel - Re: [tip:perf/urgent] perf_events: Fix time tracking for events with pid != -1 and cpu != -1

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Date:	Tue, 31 Aug 2010 09:10:59 +0800
From:	Lin Ming <lin@...g.vg>
To:	mingo@...hat.com, hpa@...or.com, eranian@...gle.com,
	linux-kernel@...r.kernel.org, a.p.zijlstra@...llo.nl,
	tglx@...utronix.de, eranian@...il.com, mingo@...e.hu
Cc:	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/urgent] perf_events: Fix time tracking for events with
 pid != -1 and cpu != -1

>
> perf_events: Fix time tracking for events with pid != -1 and cpu != -1

Hi,

I thought pid != -1 and cpu != -1 is not valid.

# perf top -p 23268 -C 1
WARNING: PID switch overriding CPU

In which case this could be valid?

Thanks,
Lin Ming

>
> Per-thread events with a cpu filter, i.e., cpu != -1, were not
> reporting correct timings when the thread never ran on the
> monitored cpu. The time enabled was reported as a negative
> value.
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