Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753796AbYJUL3X (ORCPT ); Tue, 21 Oct 2008 07:29:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752703AbYJUL3Q (ORCPT ); Tue, 21 Oct 2008 07:29:16 -0400 Received: from mu-out-0910.google.com ([209.85.134.191]:61257 "EHLO mu-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752667AbYJUL3P (ORCPT ); Tue, 21 Oct 2008 07:29:15 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=PBbOAiVgakriZ6NqAwHrSA9ZQMmqPmMr6a7tXWizx/g7iSBtDsM5Byiuih0UMpe47A pVdyWiBpBi5R7IyMWjPBApvj1BpEMzK+0maWNlkblrivsga33esTfNIYP3t4HEHMMRqJ jN2daucd3BRdtNsdo4HqpSuH96SI6NImY5OtQ= Message-ID: Date: Tue, 21 Oct 2008 13:29:12 +0200 From: "Zdenek Kabelac" To: "Chris Snook" Subject: Re: Scheduler on C2D CPU and latest 2.6.27 kernel Cc: "Linux Kernel Mailing List" , "Ingo Molnar" , "Peter Zijlstra" In-Reply-To: <48FDB7E7.4090007@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <48FDB7E7.4090007@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2030 Lines: 66 2008/10/21 Chris Snook : > Zdenek Kabelac wrote: >> >> Hi >> >> Recently I'm noticing bad behavior of the CPU scheduler on my T61 (2GB, >> C2D) >> >> It looks like Linux concentrates all running tasks on one CPU and the >> second cpu is sleeping. >> >> With recent changes to DRI - glxgears went up to 840FPS but also takes >> 100% (with Xorg) and when I run 'while :; do true; done' loop in >> parallel frame rate drops to 300FPS. >> >> But as I have C2D CPU I would expect that there should be no such >> dramatic slowdown. >> >> Xosview shows that only one CPU is fully loaded. >> >> Here are my .config scheduler options: >> >> CONFIG_HAVE_UNSTABLE_SCHED_CLOCK=y >> # CONFIG_GROUP_SCHED is not set >> CONFIG_IOSCHED_NOOP=y >> CONFIG_IOSCHED_AS=y >> CONFIG_IOSCHED_DEADLINE=y >> CONFIG_IOSCHED_CFQ=y >> CONFIG_DEFAULT_IOSCHED="cfq" >> CONFIG_SCHED_SMT=y >> # CONFIG_SCHED_MC is not set I've also tested SMT=n MC=y - with same result >> CONFIG_SCHED_HRTICK=y >> # CONFIG_NET_SCHED is not set >> CONFIG_USB_EHCI_TT_NEWSCHED=y >> CONFIG_SCHED_DEBUG=y >> CONFIG_SCHEDSTATS=y >> CONFIG_SCHED_TRACER=y >> >> >> Am I missing something? > > You're running a loop that does nothing except create new tasks that have no > scheduling history, and then disappear before the scheduler can migrate > them. > > Try running 'openssl speed' to chew up CPU. I promise you the scheduler > will behave very nicely. Well - sorry you really shouldn't promise things you cannot guarantee. It's obviously showing exactly same problem on my box. And I should add that with 2.6.27-rc8 I do not experience this behavior. Gears are showning 80% speed - but consumes only 25% and bash loop or openssl speed task do not influence its speed. (as expected with 2CPU machine) Zdenek. -- 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/