From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Wed, 16 Jul 2008 14:57:59 -0700 (PDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.168.29]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m6GLvstZ017541 for ; Wed, 16 Jul 2008 14:57:55 -0700 Received: from elf.torek.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 2B1852FB719 for ; Wed, 16 Jul 2008 14:59:01 -0700 (PDT) Received: from elf.torek.net (mail.torek.net [67.40.109.61]) by cuda.sgi.com with ESMTP id uev6Ddo3eSMI71mL for ; Wed, 16 Jul 2008 14:59:01 -0700 (PDT) Message-Id: <200807162158.m6GLwtE00281@elf.torek.net> From: Chris Torek Subject: Re: question about xfs_fsync on linux In-Reply-To: Your message of "Tue, 15 Jul 2008 12:48:30 +1000." <20080715024830.GZ29319@disturbed> Date: Wed, 16 Jul 2008 15:58:55 -0600 Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Dave Chinner Cc: xfs@oss.sgi.com >Well, you are pretty much on your own, then. Really, we cannot help >diagnose problems on old kernels with a random set of backported >patches in them. Definitely understood. I just wanted to ask that original question, really. I had assumed that the file system itself had to start any dirty-page writes, having missed the top level filemap_fdatawrite() call. We finally got a test case and did a bunch of analysis, and it turns out that the DB software is missing an fsync() call. Of course XFS won't fsync the file if you don't *ask* it to! As long as I am sending mail, there is something else I am curious about though. While this is not XFS specific, I wonder if there is any desire to have different background write frequencies on different file systems. By default, mm/page-writeback.c will start writebacks after a 30-second delay. One can tune this to any other number (via /proc/sys/vm/dirty_{expire,writeback}_centisecs), but this affects the entire system. It might be useful to be able to tune this per-FS instead. (On the other hand, perhaps if one really wants one's data journaled, one should just use a data-journaling file system....) Chris