Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756414AbZFVP34 (ORCPT ); Mon, 22 Jun 2009 11:29:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751982AbZFVP3s (ORCPT ); Mon, 22 Jun 2009 11:29:48 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:43563 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751811AbZFVP3r (ORCPT ); Mon, 22 Jun 2009 11:29:47 -0400 Date: Mon, 22 Jun 2009 17:29:37 +0200 From: Ingo Molnar To: Martin Schwidefsky Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, Rob van der Heij , Heiko Carstens , john stultz , Andi Kleen , Peter Zijlstra Subject: Re: [patch 0/2] NOHZ vs. profile/oprofile v2 Message-ID: <20090622152937.GA17512@elte.hu> References: <20090603152223.083010123@de.ibm.com> <20090622162631.4b4dcee4@skybase> <20090622144110.GA9771@elte.hu> <20090622165936.0bb776e1@skybase> <20090622150553.GA14363@elte.hu> <20090622171834.0df64aea@skybase> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090622171834.0df64aea@skybase> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1897 Lines: 52 * Martin Schwidefsky wrote: > On Mon, 22 Jun 2009 17:05:53 +0200 > Ingo Molnar wrote: > > > > > * Martin Schwidefsky wrote: > > > > > On Mon, 22 Jun 2009 16:41:10 +0200 > > > Ingo Molnar wrote: > > > > > > > Hm, this is rather ugly. Why not use hrtimers like 'perf' does when > > > > it fallback-samples based on the timer tick? > > > > > > > > That method has three advantages: > > > > > > > > - no weird hookery needed > > > > - resolution can go far beyond HZ > > > > - it is evidently dynticks-safe > > > > > > Hmm, if we replace the HZ based oprofile tick with an hrtimer we > > > should add an interface to configure the sample interval as well, > > > no? Otherwise we just replace one timer event (HZ) with another > > > (hrtimer). > > > > Even if the hrtimer is set with a 1/HZ period it's a better > > solution, as it's dynticks safe without invasive changes. > > Ok, but the patch will be quite big. All the profile_tick() calls > from the architecture files will have to be removed. [...] Hey, that's a bonus :) > [...] And if we really want to keep things separate there will be > two sets of per-cpu hrtimer, one for the old style profiler and > one for oprofile. Any preference for the user space interface to > set the sample rate? A sysctl? I dont think we want to keep things separate. Regarding old-style profiler, does anyone still use it? There's now a superior in-tree replacement for it, so we could phase it out. A sysctl sounds like the most obvious way to set the sample period - and it can default to 1/Hz. Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/