Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758285AbZF3Xgb (ORCPT ); Tue, 30 Jun 2009 19:36:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756994AbZF3XgR (ORCPT ); Tue, 30 Jun 2009 19:36:17 -0400 Received: from terminus.zytor.com ([198.137.202.10]:54320 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756459AbZF3XgQ (ORCPT ); Tue, 30 Jun 2009 19:36:16 -0400 Message-ID: <4A4AA0ED.2020304@zytor.com> Date: Tue, 30 Jun 2009 16:34:05 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Ingo Molnar CC: Tejun Heo , Christoph Lameter , Andrew Morton , linux-kernel@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, andi@firstfloor.org, tglx@linutronix.de Subject: Re: [PATCHSET] percpu: generalize first chunk allocators and improve lpage NUMA support 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> <20090630233106.GB28830@elte.hu> In-Reply-To: <20090630233106.GB28830@elte.hu> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1035 Lines: 30 Ingo Molnar wrote: > * 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 Yes, percpu area dynamic *de*-allocation would almost certainly be a nightmare. -hpa -- 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/