From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756249Ab0KSSZJ (ORCPT ); Fri, 19 Nov 2010 13:25:09 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:40265 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756042Ab0KSSZI (ORCPT ); Fri, 19 Nov 2010 13:25:08 -0500 MIME-Version: 1.0 In-Reply-To: <20101119173817.GE24450@random.random> References: <20101118111349.GG8135@csn.ul.ie> <20101119173817.GE24450@random.random> From: Linus Torvalds Date: Fri, 19 Nov 2010 09:54:27 -0800 Message-ID: Subject: Re: [PATCH 02 of 66] mm, migration: Fix race between shift_arg_pages and rmap_walk by guaranteeing rmap_walk finds PTEs created within the temporary stack To: Andrea Arcangeli Cc: Mel Gorman , linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Hugh Dickins , Rik van Riel , Dave Hansen , Benjamin Herrenschmidt , Ingo Molnar , Mike Travis , KAMEZAWA Hiroyuki , Christoph Lameter , Chris Wright , bpicco@redhat.com, KOSAKI Motohiro , Balbir Singh , "Michael S. Tsirkin" , Peter Zijlstra , Johannes Weiner , Daisuke Nishimura , Chris Mason , Borislav Petkov Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 19, 2010 at 9:38 AM, Andrea Arcangeli wrote: > > We decided the kmalloc was ok, but Linus didn't like this approach. I > kept it in my tree because I didn't want to remember when/if to add the > special check in the accurate rmap walks. I find it simpler if all > rmap walks are accurate by default. Why isn't the existing cheap solution sufficient? My opinion is still that we shouldn't add the expense to the common case, and it's the uncommon case (migration) that should just handle it. Linus From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 8FFC76B0085 for ; Fri, 19 Nov 2010 13:00:46 -0500 (EST) Received: from mail-gx0-f169.google.com (mail-gx0-f169.google.com [209.85.161.169]) (authenticated bits=0) by smtp1.linux-foundation.org (8.14.2/8.14.2/Debian-2build1) with ESMTP id oAJHxsjC029719 (version=TLSv1/SSLv3 cipher=RC4-MD5 bits=128 verify=FAIL) for ; Fri, 19 Nov 2010 09:59:55 -0800 Received: by gxk7 with SMTP id 7so3146100gxk.14 for ; Fri, 19 Nov 2010 09:59:49 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20101119173817.GE24450@random.random> References: <20101118111349.GG8135@csn.ul.ie> <20101119173817.GE24450@random.random> From: Linus Torvalds Date: Fri, 19 Nov 2010 09:54:27 -0800 Message-ID: Subject: Re: [PATCH 02 of 66] mm, migration: Fix race between shift_arg_pages and rmap_walk by guaranteeing rmap_walk finds PTEs created within the temporary stack Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: Mel Gorman , linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Hugh Dickins , Rik van Riel , Dave Hansen , Benjamin Herrenschmidt , Ingo Molnar , Mike Travis , KAMEZAWA Hiroyuki , Christoph Lameter , Chris Wright , bpicco@redhat.com, KOSAKI Motohiro , Balbir Singh , "Michael S. Tsirkin" , Peter Zijlstra , Johannes Weiner , Daisuke Nishimura , Chris Mason , Borislav Petkov List-ID: On Fri, Nov 19, 2010 at 9:38 AM, Andrea Arcangeli wrote: > > We decided the kmalloc was ok, but Linus didn't like this approach. I > kept it in my tree because I didn't want to remember when/if to add the > special check in the accurate rmap walks. I find it simpler if all > rmap walks are accurate by default. Why isn't the existing cheap solution sufficient? My opinion is still that we shouldn't add the expense to the common case, and it's the uncommon case (migration) that should just handle it. Linus -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org