From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: RE: [PATCH] Allocate vmcs pages when system booting Date: Fri, 15 Jan 2010 10:31:39 +0000 Message-ID: References: <4B5043B8020000780002A2E9@vpn.id2.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4B5043B8020000780002A2E9@vpn.id2.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jan Beulich , Yunhong Jiang Cc: "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On 15/01/2010 09:30, "Jan Beulich" wrote: >>>> "Jiang, Yunhong" 15.01.10 10:06 >>> >> b) Can we still turn to the original patch, i.e. pre-allocate all VMCS pages >> for all possible CPU? > > I'm generally opposed to pre-allocations, at least as long as all CPUs are > considered 'possible'. Building with a relatively high nr_cpus= setting > and then running on a relatively small system results in (close to) > unacceptable overhead. > > In fact it's really not clear to me why cpu_possible_map must be set to > CPU_MASK_ALL - if Linux has ways to avoid this, Xen should have too. Does Linux manage a good reliable job of cutting down cpu_possible_map? That would save cpu_possible_map in my eyes, if we could do that. Otherwise it is indeed pretty useless now. Either way, I'd like cpu hotplug notifier chains in the 4.1 development window. -- Keir