From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753844AbXDDNzf (ORCPT ); Wed, 4 Apr 2007 09:55:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753840AbXDDNzf (ORCPT ); Wed, 4 Apr 2007 09:55:35 -0400 Received: from noname.neutralserver.com ([70.84.186.210]:45613 "EHLO noname.neutralserver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753844AbXDDNze (ORCPT ); Wed, 4 Apr 2007 09:55:34 -0400 Date: Wed, 4 Apr 2007 16:55:32 +0300 From: Dan Aloni To: Andrea Arcangeli Cc: Nick Piggin , Hugh Dickins , Andrew Morton , Linus Torvalds , Linux Memory Management List , tee@sgi.com, holt@sgi.com, Linux Kernel Mailing List Subject: Re: [rfc] no ZERO_PAGE? Message-ID: <20070404135530.GA29026@localdomain> References: <20070329075805.GA6852@wotan.suse.de> <20070330024048.GG19407@wotan.suse.de> <20070404033726.GE18507@wotan.suse.de> <20070404102407.GA529@wotan.suse.de> <20070404122701.GB19587@v2.random> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070404122701.GB19587@v2.random> User-Agent: Mutt/1.5.13 (2006-08-11) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - noname.neutralserver.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [0 0] / [47 12] X-AntiAbuse: Sender Address Domain - monatomic.org X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 04, 2007 at 02:27:01PM +0200, Andrea Arcangeli wrote: > On Wed, Apr 04, 2007 at 12:24:07PM +0200, Nick Piggin wrote: > > But for a potential mainline merge, maybe starting with a CONFIG > > option is a good idea -- defaulting to off, and we could start by > > turning it on just in -rc kernels for a few releases, to get a bit > > more confidence? > > The only reason to do that is if there are many stupid apps pretending > to get meaningful information from pages that cannot contain any > information. The zero page in the anon page fault has been there > forever so... There might be a lot of applications like that, and I'm not sure that _all_ of them can be considered 'stupid' as you say. How about applications that perform mmap() and R/W random-access on large *sparse* files? (e.g. a scientific app that uses a large sparse file as a big database look-up table). As I see it, these apps would need to keep track of what's sparse and what's not... -- Dan Aloni XIV LTD, http://www.xivstorage.com da-x (at) monatomic.org, dan (at) xiv.co.il