Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759518AbYGRRAe (ORCPT ); Fri, 18 Jul 2008 13:00:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756625AbYGRRA0 (ORCPT ); Fri, 18 Jul 2008 13:00:26 -0400 Received: from smtp.ctxuk.citrix.com ([62.200.22.115]:17810 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755574AbYGRRAZ convert rfc822-to-8bit (ORCPT ); Fri, 18 Jul 2008 13:00:25 -0400 X-IronPort-AV: E=Sophos;i="4.31,211,1215388800"; d="scan'208";a="1081280" X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Subject: RE: Large increase in context switch rate Date: Fri, 18 Jul 2008 18:00:22 +0100 Message-ID: <0E902970173AF84089673FA54B7FE78A32906F@lonpexch01.citrite.net> In-Reply-To: <87mykgrxtv.fsf@basil.nowhere.org> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: Large increase in context switch rate Thread-Index: AcjoVk2UzhJQbSOATO+0B6xgaZORqQAn/czA References: <487E43D9.7080703@goop.org> <1216286250.5232.67.camel@twins><487F5F15.4050208@goop.org><0E902970173AF84089673FA54B7FE78A32906B@lonpexch01.citrite.net><487F6913.2000602@goop.org><0E902970173AF84089673FA54B7FE78A32906C@lonpexch01.citrite.net><487F6F1F.2030808@goop.org> <87mykgrxtv.fsf@basil.nowhere.org> From: "Alex Nixon (Intern)" To: "Andi Kleen" , "Jeremy Fitzhardinge" Cc: "Peter Zijlstra" , "Ingo Molnar" , "Linux Kernel Mailing List" , "Ian Campbell" X-OriginalArrivalTime: 18 Jul 2008 17:00:23.0538 (UTC) FILETIME=[C4BD8520:01C8E8F7] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1468 Lines: 45 > -----Original Message----- > From: Andi Kleen [mailto:andi@firstfloor.org] > Sent: 17 July 2008 22:43 > To: Jeremy Fitzhardinge > Cc: Alex Nixon (Intern); Peter Zijlstra; Ingo Molnar; Linux Kernel Mailing > List; Ian Campbell > Subject: Re: Large increase in context switch rate > > Jeremy Fitzhardinge writes: > > > > OK, but that still doesn't account for the relatively large increase > > from 2.6.18 -> 2.6.26. You're using HZ=100 in both cases, I presume. > > > > The other variable is NOHZ and highres timers. You could try turning > > those off in 2.6.26. Also, CONFIG_PREEMPT could well make a > > difference. 2.6.18-xen doesn't support CONFIG_PREEMPT at all, but > > pvops(-xen) does. > > If it's that easily reproducible you could just bisect it? > > -Andi I've bisected the majority of the increase down to some time between 2.6.18 and 2.6.19 - kernbench results are: Kernel version Elapsed User System Context Switches V2.6.18 232 427 28 32713 V2.6.19 232 429 28 52812 NOHZ and highres timers are disabled wherever available, HZ=100, and CONFIG_PREEMPT_VOLUNTARY=y Will continue further on Monday. - Alex -- 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/