From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756550AbXKIUYt (ORCPT ); Fri, 9 Nov 2007 15:24:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751537AbXKIUYk (ORCPT ); Fri, 9 Nov 2007 15:24:40 -0500 Received: from madara.hpl.hp.com ([192.6.19.124]:63263 "EHLO madara.hpl.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751523AbXKIUYj (ORCPT ); Fri, 9 Nov 2007 15:24:39 -0500 Date: Fri, 9 Nov 2007 12:17:11 -0800 From: Stephane Eranian To: Thomas Gleixner Cc: Peter Zijlstra , perfmon2-devel@lists.sourceforge.net, perfmon@napali.hpl.hp.com, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, Ingo Molnar Subject: Re: conflict between tickless and perfmon2 Message-ID: <20071109201711.GA20390@frankl.hpl.hp.com> Reply-To: eranian@hpl.hp.com References: <20071109104438.GB18909@frankl.hpl.hp.com> <1194605991.6289.162.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i Organisation: HP Labs Palo Alto Address: HP Labs, 1U-17, 1501 Page Mill road, Palo Alto, CA 94304, USA. E-mail: eranian@hpl.hp.com X-HPL-MailScanner: Found to be clean X-HPL-MailScanner-From: eranian@hpl.hp.com Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Thomas, On Fri, Nov 09, 2007 at 07:40:31PM +0100, Thomas Gleixner wrote: > > > > It looks like a solution would be to change the implementation of > > > timeout-based switching to use HR timers instead. Similar to what is > > > done for ITIMER_REAL and ITIMER_VIRTUAL. > > Using a hrtimer is perfrectly fine, I'd say it's preferred over hooks in > some code which has absoluty no guarantee of being executed periodically > or even executed at all. OTOH it seems rather stupid to measure stuff > while the system is idle and doing nothing. > I'll start looking into this soon. To answer your point about idle, this is not because the core is idle that counters do not capture events related to buses or caches for instance. -- -Stephane