From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932079AbVHXUbU (ORCPT ); Wed, 24 Aug 2005 16:31:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932124AbVHXUbU (ORCPT ); Wed, 24 Aug 2005 16:31:20 -0400 Received: from omx2-ext.sgi.com ([192.48.171.19]:37030 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S932079AbVHXUbT (ORCPT ); Wed, 24 Aug 2005 16:31:19 -0400 Date: Wed, 24 Aug 2005 13:31:07 -0700 From: Paul Jackson To: Nick Piggin Cc: dino@in.ibm.com, paulus@samba.org, akpm@osdl.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, torvalds@osdl.org, mingo@elte.hu, hawkes@sgi.com Subject: Re: [PATCH 2.6.13-rc6] cpu_exclusive sched domains build fix Message-Id: <20050824133107.2ca733c3.pj@sgi.com> In-Reply-To: <430C617E.8080002@yahoo.com.au> References: <20050824111510.11478.49764.sendpatchset@jackhammer.engr.sgi.com> <20050824112640.GB5197@in.ibm.com> <20050824044648.66f7e25a.pj@sgi.com> <430C617E.8080002@yahoo.com.au> Organization: SGI X-Mailer: Sylpheed version 2.0.0beta5 (GTK+ 2.4.9; i686-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 X-Mailing-List: linux-kernel@vger.kernel.org Nick wrote: > I get the feeling that exclusive cpusets should just be > completely disabled for 2.6.13 No no - not disable exclusive cpusets - disable using them to try to define sched domains. That is, I hope you mean that Dinakar's patch that uses cpu_exclusive cpusets to define sched domains should be disabled for 2.6.13. For what they were worth (not a whole lot, granted), cpu_exclusive cpusets have been in the kernel since 2.6.12. They just didn't have any affect in the placement of sched domains. So long as they continue to do not a whole lot, I see more risk than gain in disabling them for 2.6.13. So long as the cpuset code stops making any calls to partition_sched_domains() whatsoever, then we should be back where we were in 2.6.12, so far as the scheduler is concerned - right? I hope that the following (untested, unbuilt) patch, that I suggested in my "Mon, 22 Aug 2005 13:38:23 -0700" message best meets you suggestion above ... and I quote: ========== The safest, mind numbingly simple thing to do that would avoid the oops that Hawkes reported is to simply not have the cpuset code call the code to setup a dynamic sched domain. This is choice (2) above, and could be done at the last hour with relative safety. Here is an untested patch that does (2): ===== Index: linux-2.6.13-cpuset-mempolicy-migrate/kernel/cpuset.c =================================================================== --- linux-2.6.13-cpuset-mempolicy-migrate.orig/kernel/cpuset.c +++ linux-2.6.13-cpuset-mempolicy-migrate/kernel/cpuset.c @@ -627,6 +627,15 @@ static int validate_change(const struct * Call with cpuset_sem held. May nest a call to the * lock_cpu_hotplug()/unlock_cpu_hotplug() pair. */ + +/* + * Hack to avoid 2.6.13 partial node dynamic sched domain bug. + * Disable letting 'cpu_exclusive' cpusets define dynamic sched + * domains, until the sched domain can handle partial nodes. + * Remove this ifdef hackery when sched domains fixed. + */ +#define DISABLE_EXCLUSIVE_CPU_DOMAINS 1 +#ifdef DISABLE_EXCLUSIVE_CPU_DOMAINS static void update_cpu_domains(struct cpuset *cur) { struct cpuset *c, *par = cur->parent; @@ -667,6 +676,11 @@ static void update_cpu_domains(struct cp partition_sched_domains(&pspan, &cspan); unlock_cpu_hotplug(); } +#else +static void update_cpu_domains(struct cpuset *cur) +{ +} +#endif static int update_cpumask(struct cpuset *cs, char *buf) { ===== -- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson 1.925.600.0401