Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757879AbZFVPgW (ORCPT ); Mon, 22 Jun 2009 11:36:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753011AbZFVPgN (ORCPT ); Mon, 22 Jun 2009 11:36:13 -0400 Received: from mtagate4.de.ibm.com ([195.212.29.153]:43234 "EHLO mtagate4.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751811AbZFVPgM (ORCPT ); Mon, 22 Jun 2009 11:36:12 -0400 Date: Mon, 22 Jun 2009 17:36:11 +0200 From: Martin Schwidefsky To: Ingo Molnar 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: <20090622173611.3b583c95@skybase> In-Reply-To: <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> <20090622152937.GA17512@elte.hu> Organization: IBM Corporation X-Mailer: Claws Mail 3.7.1 (GTK+ 2.16.2; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2367 Lines: 68 On Mon, 22 Jun 2009 17:29:37 +0200 Ingo Molnar wrote: > > * 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 :) It would remove some oddball code :-) > > [...] 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. Well, for my part I won't miss it. But to be able to remove the profile_tick() calls from the architectures I either have to rip out the old profiler now, or adapt it to use hrtimer as well. > A sysctl sounds like the most obvious way to set the sample period - > and it can default to 1/Hz. Agreed. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- 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/