linux-kernel - perf_events: issue with scaling information

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Message-ID: <7c86c4470910080712v730a4c7fxbd71d97b605a1f6e@mail.gmail.com>
Date:	Thu, 8 Oct 2009 16:12:33 +0200
From:	stephane eranian <eranian@...glemail.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	perfmon2-devel <perfmon2-devel@...ts.sourceforge.net>
Subject: perf_events: issue with scaling information

Hi,

With libpfm4, I have developed a set of examples which are using
perf_events to demonstrate typical counting and sampling scenarios.

In two of the sampling program, it appears time_enabled, time_running
included in the samples are incorrect.

The program notify_self.c uses IOC_REFRESH to get a notification for
each sample. The first sample comes out with time_running = time_enabled =0,
subsequent samples return non-zero information. I suspect something is
wrong initially because of IOC_REFRESH. This is using an event group.

The program task_smpl.c is sampling another process. Although the scaling
information is requested, all samples come out with time_running =
time_enabled=0.
The rest of the sample is correct, so it's not like I am not correctly
reading the
sample. The program is using an event group.

I suspect both issues may be related.

You can obtain the test programs (which are open-source!), by cloning
the GIT tree
at:
         git://perfmon2.git.sourceforge.net/gitroot/perfmon2/libpfm4

Thanks.
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