From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCHSET] percpu: generalize first chunk allocators and improve lpage NUMA support Date: Wed, 1 Jul 2009 00:31:38 +0200 Message-ID: <20090630223138.GH1241@elte.hu> References: <1245850216-31653-1-git-send-email-tj@kernel.org> <20090624165508.30b88343.akpm@linux-foundation.org> <20090629163937.94c8cedd.akpm@linux-foundation.org> <20090630191517.GB20567@elte.hu> <20090630213146.GA17492@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx3.mail.elte.hu ([157.181.1.138]:53224 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753717AbZF3Wbv (ORCPT ); Tue, 30 Jun 2009 18:31:51 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: Christoph Lameter Cc: Andrew Morton , tj@kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, andi@firstfloor.org, hpa@zytor.com, tglx@linutronix.de * Christoph Lameter wrote: > On Tue, 30 Jun 2009, Ingo Molnar wrote: > > > But what if not? What if the kernel can run on up to 4096 CPUs > > and runs on a big box. Why should a virtual machine have the > > illogical choice between either wasting a lot of RAM > > preallocating stuff, or limiting its own extendability. > > The kernel may be able to run on 4096 but the machines config > information that is available via ACPI knows how many processors > the machine we are booting on is able to add. I think we might be talking past each other. The usecase i'm talking about is to boot a generic, many-CPUs-capable kernel in a guest image. How would you allow that guest to stay on 2 virtual CPUs but still be able to hot-plug many other CPUs if the guest context rises above its original CPU utilization? Ingo