linux-kernel - Re: [patch] perf timechart: Add a power-only mode

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Message-ID: <20090924155108.38777ef5@infradead.org>
Date:	Thu, 24 Sep 2009 15:51:08 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, peterz@...radead.org
Subject: Re: [patch] perf timechart: Add a power-only mode

On Thu, 24 Sep 2009 15:47:01 +0200
Eric Dumazet <eric.dumazet@...il.com> wrote:

> > -	for (cpu = 0; cpu < numcpus; cpu++) {
> > +	for (cpu = 0; cpu <= numcpus; cpu++) {
> 
> hmm, why test is now "cpu <= numcpus" ?

at this point numcpus is the highest number cpu...
and the graph would miss the "closing" frequency.


> > fopen("/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies",
> > "r");
> 
> if this cpu is offline

1) taking cpu 0 offline is stupid ;-)
(really, don't do that, there's only bad things to come from it)
2) if that file does not exist the fallback is graceful, we just use
the highest frequency we saw in the trace instead.

> 
>  /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies:
> No such file or directory

-- 
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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