From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754477AbZBRGoY (ORCPT ); Wed, 18 Feb 2009 01:44:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752775AbZBRGoP (ORCPT ); Wed, 18 Feb 2009 01:44:15 -0500 Received: from terminus.zytor.com ([198.137.202.10]:47078 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752336AbZBRGoO (ORCPT ); Wed, 18 Feb 2009 01:44:14 -0500 Message-ID: <499BAD54.3050108@zytor.com> Date: Tue, 17 Feb 2009 22:40:20 -0800 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Rusty Russell CC: Tejun Heo , Ingo Molnar , Thomas Gleixner , x86@kernel.org, Linux Kernel Mailing List , Jeremy Fitzhardinge , cpw@sgi.com Subject: Re: #tj-percpu has been rebased References: <49833350.1020809@kernel.org> <200902170952.21063.rusty@rustcorp.com.au> <4999F693.5000105@zytor.com> <200902181455.11572.rusty@rustcorp.com.au> In-Reply-To: <200902181455.11572.rusty@rustcorp.com.au> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Rusty Russell wrote: >>> >> num_possible_cpus() can be very large though, so in many cases the >> likelihood of finding that many pages approach zero. Furthermore, >> num_possible_cpus() may be quite a bit larger than the actual number of >> CPUs in the system. > > Sure, so we end up at vmalloc. No worse, but simpler and much better if we > *can* do it. > If the likelihood is near zero, then you're wasting opportunities to do it better. If we have compact per-cpu virtual areas then we can use large pages if we know we'll have large percpu areas. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.