From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754135Ab1EWI3f (ORCPT ); Mon, 23 May 2011 04:29:35 -0400 Received: from swampdragon.chaosbits.net ([90.184.90.115]:19122 "EHLO swampdragon.chaosbits.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753197Ab1EWI3e (ORCPT ); Mon, 23 May 2011 04:29:34 -0400 Date: Mon, 23 May 2011 10:22:02 +0200 (CEST) From: Jesper Juhl To: "D. Jansen" cc: Valdis.Kletnieks@vt.edu, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, tytso@mit.edu Subject: Re: [rfc] Ignore Fsync Calls in Laptop_Mode In-Reply-To: Message-ID: References: <9534.1305905293@localhost> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="8323328-2085992460-1306138922=:3148" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323328-2085992460-1306138922=:3148 Content-Type: TEXT/PLAIN; charset=UTF-8 Content-Transfer-Encoding: 8BIT On Fri, 20 May 2011, D. Jansen wrote: > On Fri, May 20, 2011 at 5:28 PM, wrote: > > On Thu, 19 May 2011 15:34:46 +0200, Dennis Jansen said: > > > >> Testing: > >> I've been using this workaround on my netbook for over six months now. > >> It works as expected for me with all software in a Ubuntu 9.10 > >> environment and saves me at least 0.5 Watt or roughly 10 % battery > >> time - without destroying my hard disk. I have seen no negative side > >> effects. > > > > How much destructive testing did you do?  In the 6 months, how many times did > > the system crash (or had the battery pulled out, or whatever) while large > > amounts of data were still pending after apps thought they were fsync'ed? How > > much crash testing was done against apps that use fsync for ordering or > > correctness reasons? > > I don't see the point in verifying the obvious. Of course applications > that rely on fsync will lose data. > The real problem comes with ordering correctness, which could actually > _destroy previous data_ as well. > In my scenario (office applications, browsing) I have not hit such a problem. > > Does anyone know a Linux app that actually does rely on ordering > correctness? Is that one which is used on a laptop? In laptop mode? > (-> when on battery?) Because so far the discussion seems to be > running in circles around Alan's mailer daemon. I would just shut that > down on enabling laptop mode. Problem solved. But I don't run that on > my laptop, anyway, esp. in laptop mode. I wonder who would, too. > PostgreSQL's Write Ahead Log (WAL) would be one such example as far as I can see ( http://www.westnet.com/~gsmith/content/postgresql/TuningPGWAL.htm ). And yes, people run that on laptops while on battery (I know that for a fact since I do that myself). -- Jesper Juhl http://www.chaosbits.net/ Don't top-post http://www.catb.org/jargon/html/T/top-post.html Plain text mails only, please. --8323328-2085992460-1306138922=:3148--