linux-kernel - Re: [patch 0/3] [Announcement] Performance Counters for Linux

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Message-ID: <20081205070042.0b8a3ef5@infradead.org>
Date:	Fri, 5 Dec 2008 07:00:42 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	David Miller <davem@...emloft.net>
Cc:	a.p.zijlstra@...llo.nl, paulus@...ba.org, mingo@...e.hu,
	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org, akpm@...ux-foundation.org,
	eranian@...glemail.com, dada1@...mosbay.com,
	robert.richter@....com, hpa@...or.com, rostedt@...dmis.org
Subject: Re: [patch 0/3] [Announcement] Performance Counters for Linux

On Fri, 05 Dec 2008 00:07:16 -0800 (PST)
David Miller <davem@...emloft.net> wrote:

> These things aren't measuring time, or even just cycles, they
> are measuring things like L2 cache misses, cpu cycles, and
> other similar kinds of events.
> 
> So these counters are going to measure all of the damn crap
> assosciated with doing the read() call as well as the real work
> the task does.

as you said before, not if you do the read() from a thread that's
exempt from the profiling.

-- 
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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