Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932711Ab3G3Jf1 (ORCPT ); Tue, 30 Jul 2013 05:35:27 -0400 Received: from merlin.infradead.org ([205.233.59.134]:41788 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758438Ab3G3JfZ (ORCPT ); Tue, 30 Jul 2013 05:35:25 -0400 Date: Tue, 30 Jul 2013 11:35:19 +0200 From: Peter Zijlstra To: Ethan Zhao Cc: Thomas Gleixner , Ingo Molnar , LKML , johlstei@codeaurora.org, Yinghai Lu , Jin Feng Subject: Re: [PATCH V3]hrtimer: Fix a performance regression by disable reprogramming in remove_hrtimer Message-ID: <20130730093519.GP3008@twins.programming.kicks-ass.net> References: <1374955447-5051-1-git-send-email-ethan.kernel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1287 Lines: 33 On Tue, Jul 30, 2013 at 05:12:49PM +0800, Ethan Zhao wrote: > On Mon, Jul 29, 2013 at 6:18 PM, Thomas Gleixner wrote: > > The test case does not involve anything hrtimer related. Do you have > > CONFIG_SCHED_HRTICK enabled? > > > > Yes. it is default configured in stable release. > CONFIG_SCHED_HRTICK=y Should still be disabled by default even if supported: # grep HRTICK kernel/sched/features.h SCHED_FEAT(HRTICK, false) > > First of all we want to know, which particular hrtimer is causing that > > issue. If it is the hrtick one, then I really have to ask why you want > > to use it at all in such a high performance scenario. > > > > Any advice about the HZ in high performance scenario ? hrtimer tick > Is not fit for high performance ? Hence why its disabled, programming the timer hardware is too expensive. But since you didn't even know that I suspect you aren't in fact using it. It would be good if you could do what Thomas suggested and look at which timer is actually active during your workload. -- 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/