Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261581AbVDDGjy (ORCPT ); Mon, 4 Apr 2005 02:39:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261568AbVDDGjZ (ORCPT ); Mon, 4 Apr 2005 02:39:25 -0400 Received: from mx1.elte.hu ([157.181.1.137]:10924 "EHLO mx1.elte.hu") by vger.kernel.org with ESMTP id S261561AbVDDGjU (ORCPT ); Mon, 4 Apr 2005 02:39:20 -0400 Date: Mon, 4 Apr 2005 08:39:10 +0200 From: Ingo Molnar To: "Chen, Kenneth W" Cc: Paul Jackson , torvalds@osdl.org, nickpiggin@yahoo.com.au, akpm@osdl.org, linux-kernel@vger.kernel.org Subject: Re: [patch] sched: auto-tune migration costs [was: Re: Industry db benchmark result on recent 2.6 kernels] Message-ID: <20050404063910.GA23094@elte.hu> References: <20050403142959.GB22798@elte.hu> <200504040131.j341Vlg31981@unix-os.sc.intel.com> <20050404062414.GA22664@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050404062414.GA22664@elte.hu> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1412 Lines: 32 * Ingo Molnar wrote: > > a numa scheduler domain at the top level and cache_hot_time will be > > set to 0 in that case on smp box. Though this will be a mutt point > > with recent patch from Suresh Siddha for removing the extra bogus > > scheduler domains. > > http://marc.theaimsgroup.com/?t=111240208000001&r=1&w=2 > > at first sight the dummy domain should not be a problem, [...] at second sight, maybe it could be a problem after all. It's safe is load_balance(), where task_hot() should never happen to be called for the dummy domain. (because the dummy domain has only one CPU group on such boxes) But if the dummy domain has SD_WAKE_AFFINE set then it's being considered for passive migration, and a value of 0 means 'can always migrate', and in situations where other domains signalled 'task is too hot', this domain may still override the decision (incorrectly). So the safe value for dummy domains would a cacheflush time of 'infinity' - to make sure migration decisions are only done via other domains. I've changed this in my tree - migration_cost[] is now initialized to -1LL, which should solve this problem. Ingo - 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/