From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arjan van de Ven Subject: Re: [patch 0/3] [Announcement] Performance Counters for Linux Date: Fri, 5 Dec 2008 07:00:42 -0800 Message-ID: <20081205070042.0b8a3ef5@infradead.org> References: <1228461385.18899.13.camel@twins> <18744.57057.243817.407691@cargo.ozlabs.ibm.com> <1228464216.18899.18.camel@twins> <20081205.000716.40104924.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from casper.infradead.org ([85.118.1.10]:52273 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752523AbYLEO7h (ORCPT ); Fri, 5 Dec 2008 09:59:37 -0500 In-Reply-To: <20081205.000716.40104924.davem@davemloft.net> Sender: linux-arch-owner@vger.kernel.org List-ID: To: David Miller Cc: a.p.zijlstra@chello.nl, paulus@samba.org, mingo@elte.hu, tglx@linutronix.de, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, akpm@linux-foundation.org, eranian@googlemail.com, dada1@cosmosbay.com, robert.richter@amd.com, hpa@zytor.com, rostedt@goodmis.org On Fri, 05 Dec 2008 00:07:16 -0800 (PST) David Miller 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