linux-kernel - Re: perf timechart segfault

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Date:	Sun, 24 Oct 2010 10:03:56 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Sitsofe Wheeler <sitsofe@...oo.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: perf timechart segfault

On Sun, 24 Oct 2010 17:23:02 +0100
Sitsofe Wheeler <sitsofe@...oo.com> wrote:

> Hi,
> 
> I've run into a couple of issues using perf timechart:
> 
> 1. (On 2.6.36) If I issue
>    echo 0 > /proc/sys/kernel/perf_event_paranoid
>    as root before running
>    perf timechart record echo
>    as a normal user the following is printed:
> 
>    Fatal: Permission error - are you root?
>   	 Consider tweaking /proc/sys/kernel/perf_event_paranoid.
> 
>    Shouldn't it just say it needs root permissions for a timechart
>    record?

timechart needs root perms since it gets very global data.

> 
> 2. (On -tip) Running
>    perf timechart record echo
>    outputs
>    invalid or unsupported event: 'power:power_start'
>    Run 'perf list' for a list of valid events

tip broke ABI :-(
That's one for Ingo to deal with for now.

> 
> 3. (On 2.6.36) I can't seem to convince timechart to ever capture more
>    than 34000 samples. When trying to record using
>    perf timechart record -fga sleep 10
>    and then creating a graph using perf timechart, it only ever
> outputs a few seconds worth.

does this happen even without the "fga" ?
I've used timechart to capture a minute of data before
(but... you need a rather quiet system for that to be useful.... you
otherwise get an impossibly big SVG file)


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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