From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754180AbYG1NWR (ORCPT ); Mon, 28 Jul 2008 09:22:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750823AbYG1NWD (ORCPT ); Mon, 28 Jul 2008 09:22:03 -0400 Received: from ozlabs.org ([203.10.76.45]:39084 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750790AbYG1NWB (ORCPT ); Mon, 28 Jul 2008 09:22:01 -0400 From: Rusty Russell To: Ingo Molnar Subject: Re: [git pull] cpus4096 fixes Date: Mon, 28 Jul 2008 23:21:53 +1000 User-Agent: KMail/1.9.9 Cc: Linus Torvalds , linux-kernel@vger.kernel.org, Andrew Morton , Mike Travis References: <20080727190601.GA764@elte.hu> <200807281053.58267.rusty@rustcorp.com.au> <20080728081639.GA27708@elte.hu> In-Reply-To: <20080728081639.GA27708@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200807282321.53892.rusty@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 28 July 2008 18:16:39 Ingo Molnar wrote: > * Rusty Russell wrote: > > Mike: I now think the right long-term answer is Linus' dense cpumap > > idea + a convenience allocator for cpumasks. We sweep the kernel for > > all on-stack vars and replace them with one or the other. Thoughts? > > The dense cpumap for constant cpumasks is OK as it's clever, compact and > static. > > All-dynamic allocator for on-stack cpumasks ... is a less obvious > choice. Sorry, I was unclear. "long-term" == "more than 4096 CPUs", since I thought that was Mike's aim. If we only want to hack up 4k CPUS and stop, then I understand the current approach. If we want huge cpu numbers, I think cpumask_alloc/free gives the clearest code. So our approach is backwards: let's do that *then* put ugly hacks in if it's really too slow. Cheers, Rusty.