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 01:31:06 +0200 Message-ID: <20090630233106.GB28830@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> <4A4A9DC6.6020003@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx3.mail.elte.hu ([157.181.1.138]:49655 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754974AbZF3XbS (ORCPT ); Tue, 30 Jun 2009 19:31:18 -0400 Content-Disposition: inline In-Reply-To: <4A4A9DC6.6020003@kernel.org> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Tejun Heo Cc: Christoph Lameter , Andrew Morton , linux-kernel@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, andi@firstfloor.org, hpa@zytor.com, tglx@linutronix.de * Tejun Heo wrote: > Hello, Christoph. > > Christoph Lameter wrote: > > I looked at allocating for online cpus only a couple of years > > back but at that per cpu state was kept for offlined cpus in per > > cpu areas. There are numerous assumptions in per cpu handling > > all over the kernel that a percpu area is always available. > > The plan is to allocate and keep percpu areas for cpus which have > ever been up. There'll be no taking down of percpu areas. > Conversion from possible to has_ever_been_up should be much easier > than possible -> online. State keeping will work fine too. That sounds like a very sane plan. Ingo