Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757600AbYGJR0S (ORCPT ); Thu, 10 Jul 2008 13:26:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751639AbYGJR0A (ORCPT ); Thu, 10 Jul 2008 13:26:00 -0400 Received: from gw.goop.org ([64.81.55.164]:34057 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751511AbYGJRZ6 (ORCPT ); Thu, 10 Jul 2008 13:25:58 -0400 Message-ID: <48764619.9040708@goop.org> Date: Thu, 10 Jul 2008 10:25:45 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Christoph Lameter CC: Mike Travis , "Eric W. Biederman" , "H. Peter Anvin" , Arjan van de Ven , Ingo Molnar , Andrew Morton , Jack Steiner , linux-kernel@vger.kernel.org, Rusty Russell Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses References: <20080709165129.292635000@polaris-admin.engr.sgi.com> <20080709200757.GD14009@elte.hu> <48751B57.8030605@goop.org> <20080709133958.612635f0@infradead.org> <4875231F.1020506@zytor.com> <487524A0.6020304@goop.org> <487529AE.3060505@zytor.com> <48753A71.2030006@zytor.com> <48763732.7020805@sgi.com> <487641D6.5060206@goop.org> <48764307.20905@linux-foundation.org> In-Reply-To: <48764307.20905@linux-foundation.org> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 974 Lines: 26 Christoph Lameter wrote: > Jeremy Fitzhardinge wrote: > > >> You want to virtually map the percpu area? How and when would it get >> extended? >> > > It would get extended when cpu_alloc() is called and the allocator finds that there is no per cpu memory available. > Which, I take it, allocates percpu memory. It would have the same caveats as vmalloc memory, with respect to accessing it during fault handlers and nmi handlers, I take it. How would cpu_alloc() actually get used? It doesn't make much sense for general code, since we don't have the notion of a percpu pointer to memory (vs a pointer to percpu memory). Is the intended use for allocating percpu memory in modules? What other uses? J -- 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/