From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262600AbVHDQay (ORCPT ); Thu, 4 Aug 2005 12:30:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262598AbVHDQax (ORCPT ); Thu, 4 Aug 2005 12:30:53 -0400 Received: from fmr21.intel.com ([143.183.121.13]:15034 "EHLO scsfmr001.sc.intel.com") by vger.kernel.org with ESMTP id S262600AbVHDQ3g (ORCPT ); Thu, 4 Aug 2005 12:29:36 -0400 Date: Thu, 4 Aug 2005 09:28:41 -0700 From: Ashok Raj To: Andi Kleen Cc: Ashok Raj , Andrew Morton , zwane@arm.linux.org.uk, linux-kernel@vger.kernel.org Subject: Re: [patch 3/8] x86_64:Dont call enforce_max_cpus when hotplug is enabled Message-ID: <20050804092841.A15274@unix-os.sc.intel.com> References: <20050801202017.043754000@araj-em64t> <20050801203011.178499000@araj-em64t> <20050804104110.GB97893@muc.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <20050804104110.GB97893@muc.de>; from ak@muc.de on Thu, Aug 04, 2005 at 12:41:10PM +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 04, 2005 at 12:41:10PM +0200, Andi Kleen wrote: > On Mon, Aug 01, 2005 at 01:20:20PM -0700, Ashok Raj wrote: > > No need to enforce_max_cpus when hotplug code is enabled. This > > nukes out cpu_present_map and cpu_possible_map making it impossible to add > > new cpus in the system. > > Hmm - i think there was some reason for this early zeroing, > but I cannot remember it right now. > > It might be related to some checks later that check max possible cpus. > > So it would be still good to have some way to limit max possible cpus. > Maybe with a new option? The only useful thing with enfore_max() is that cpu_possible_map is trimmed so some resource allocations that use for_each_cpu() for upfront allocation wont allocate resources. Currently i see max_cpus only limiting boot-time start, none trim cpu_possible which is done in only x86_64. max_cpu is still honored, just that for initial boot. I would think maybe remove enforce_max_cpus() altogether like other archs instead of adding one more just for x86_64. Maybe we should add only if there is a need, instead of adding and finding no-one using it and finally removing it very soon. > > -Andi -- Cheers, Ashok Raj - Open Source Technology Center