Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753727AbYJBIM5 (ORCPT ); Thu, 2 Oct 2008 04:12:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752792AbYJBIMn (ORCPT ); Thu, 2 Oct 2008 04:12:43 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:36665 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752729AbYJBIMl (ORCPT ); Thu, 2 Oct 2008 04:12:41 -0400 Date: Thu, 2 Oct 2008 10:12:31 +0200 From: Ingo Molnar To: Chuck Ebbert Cc: linux-kernel@vger.kernel.org, Arjan van de Ven , "H. Peter Anvin" , Thomas Gleixner Subject: Re: [patch x86/core] x86: allow number of additional hotplug CPUs to be set at compile time Message-ID: <20081002081231.GC17695@elte.hu> References: <20081001191945.4182d0be@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081001191945.4182d0be@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1725 Lines: 43 * Chuck Ebbert wrote: > From: Chuck Ebbert > > x86: allow number of additional hotplug CPUs to be set at compile time > > The default number of additional CPU IDs for hotplugging is determined > by asking ACPI or mptables how many "disabled" CPUs there are in the > system, but many systems get this wrong so that e.g. a uniprocessor > machine gets an extra CPU allocated and never switches to single CPU > mode. > > And sometimes CPU hotplugging is enabled only for suspend/hibernate > anyway, so the additional CPU IDs are not wanted. Allow the number to > be set to zero at compile time. > > Also, force the number of extra CPUs to zero if hotplugging is > disabled which allows removing some conditional code. > > Tested on uniprocessor x86_64 that ACPI claims has a disabled > processor, with CPU hotplugging configured. > > ("After" has the number of additional CPUs set to 0) > Before: NR_CPUS: 512, nr_cpu_ids: 2, nr_node_ids 1 > After: NR_CPUS: 512, nr_cpu_ids: 1, nr_node_ids 1 > > Signed-off-by: Chuck Ebbert hm, wouldnt this option kill 'real' hot-plug CPUs (how rare they might be) which are properly enumerated in the BIOS tables? i dont mind having a facility to disable real CPU hotplug, but the CONFIG_HOTPLUG_DEFAULT_ADDITIONAL_CPUS does not spell that out clearly IMO. Something like CONFIG_HOTPLUG_RESTRICT_TO_BOOTUP_CPUS=y would be more appropriately named i think? 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/