Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752720AbYJaTIm (ORCPT ); Fri, 31 Oct 2008 15:08:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751373AbYJaTIe (ORCPT ); Fri, 31 Oct 2008 15:08:34 -0400 Received: from mx2.redhat.com ([66.187.237.31]:57185 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750842AbYJaTId (ORCPT ); Fri, 31 Oct 2008 15:08:33 -0400 Date: Fri, 31 Oct 2008 15:08:20 -0400 From: Dave Jones To: Suresh Siddha Cc: Peter Zijlstra , Linux Kernel , Ingo Molnar Subject: Re: sched domains oddness. Message-ID: <20081031190820.GA14435@redhat.com> Mail-Followup-To: Dave Jones , Suresh Siddha , Peter Zijlstra , Linux Kernel , Ingo Molnar References: <20081031162443.GA29885@redhat.com> <1225471911.7803.1596.camel@twins> <20081031170928.GB10468@linux-os.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081031170928.GB10468@linux-os.sc.intel.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2057 Lines: 50 On Fri, Oct 31, 2008 at 10:09:29AM -0700, Suresh Siddha wrote: > On Fri, Oct 31, 2008 at 09:51:51AM -0700, Peter Zijlstra wrote: > > On Fri, 2008-10-31 at 12:24 -0400, Dave Jones wrote: > > > The attached dmesg comes from my dual core laptop running 2.6.27 > > > What's up with all the sched domains transitions at the bottom? > > > This was just a boot up from power off, no suspend/resume or anything funky. > > > > > CPU0 attaching NULL sched-domain. > > > CPU1 attaching NULL sched-domain. > > > CPU0 attaching sched-domain: > > > domain 0: span 0-1 level MC > > > groups: 0 1 > > > domain 1: span 0-1 level NODE > > > groups: 0-1 > > > CPU1 attaching sched-domain: > > > domain 0: span 0-1 level MC > > > groups: 1 0 > > > domain 1: span 0-1 level NODE > > > groups: 0-1 > > > > 3x > > > > looks like someone is triggering rebuild_sched_domains(), is something > > poking cpusetfs files or flipping between sched_mc settings? > > I remember someone mentioning that some distro's started setting > sched_mc_power_savings to '1' by default during boot. On a dual-core > laptop, this will not give any advantage. > > I have to fix the code to not export this tunable, when we have only > socket in the system. > > Dave, Is your distro also setting this tunable blindly during boot :( So I found something (pm-utils) that seems to have mechanism for changing sched_mc Though it's not obvious to me how this is getting invoked. One question I have though is that to set this sensibly, it seems that userspace is going to have to have understanding of how the topology is layed out. Given the kernel already knows, perhaps not making that sysfs file present on systems where it doesn't make sense would be simpler ? Dave -- http://www.codemonkey.org.uk -- 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/