From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263317AbTJQGqs (ORCPT ); Fri, 17 Oct 2003 02:46:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263319AbTJQGqs (ORCPT ); Fri, 17 Oct 2003 02:46:48 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:26296 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S263317AbTJQGqr (ORCPT ); Fri, 17 Oct 2003 02:46:47 -0400 Date: Fri, 17 Oct 2003 08:46:45 +0200 From: Jens Axboe To: "Mudama, Eric" Cc: Greg Stark , Linux Kernel Subject: Re: [PATCH] ide write barrier support Message-ID: <20031017064645.GX1128@suse.de> References: <785F348679A4D5119A0C009027DE33C105CDB2C5@mcoexc04.mlm.maxtor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <785F348679A4D5119A0C009027DE33C105CDB2C5@mcoexc04.mlm.maxtor.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 16 2003, Mudama, Eric wrote: > > On Tue, Oct 14 2003, Greg Stark wrote: > > Jens Axboe writes: > > > There's also the case of files opened with O_SYNC. Would inserting a > > > write barrier after every write to such a file destroy performance? > > > > If it's mainly sequential io, then no it won't destroy performance. It > > will be lower than without the cache flush of course. > > If you flush a cache after every command in a sequential write, yes, you'll > destroy performance. How much you destroy it is a function of command size > relative to track size, and the RPM of the drive. Yes you are right, my logic was a bit backwards. But you don't have to issue a flush after every write, thankfully. But lets still not forget that performance means nothing if integrity isn't guarenteed. -- Jens Axboe