From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261324AbVFMUaO (ORCPT ); Mon, 13 Jun 2005 16:30:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261317AbVFMU1g (ORCPT ); Mon, 13 Jun 2005 16:27:36 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:46253 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S261322AbVFMUYu (ORCPT ); Mon, 13 Jun 2005 16:24:50 -0400 Date: Mon, 13 Jun 2005 22:25:56 +0200 From: Jens Axboe To: Alan Cox Cc: Nick Piggin , Ondrej Zary , Grant Coady , Linux Kernel Mailing List Subject: Re: Odd IDE performance drop 2.4 vs 2.6? Message-ID: <20050613202555.GB27774@suse.de> References: <42AD6362.1000109@rainbow-software.org> <1118669975.13260.23.camel@localhost.localdomain> <42AD92F2.7080108@yahoo.com.au> <1118675343.13773.1.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1118675343.13773.1.camel@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 13 2005, Alan Cox wrote: > On Llu, 2005-06-13 at 15:06, Nick Piggin wrote: > > > Make sure you have pre-empt disabled and the antcipatory I/O scheduler > > > disabled. > > > > > I don't think that those could explain it. > > Try it and see. The anticipatory I/O scheduler does horrible things to > my IDE streaming performance numbers and to swap performance. It tries > to merge I/O by delaying it which is deeply ungood when it comes to IDE > streaming even if its good for general I/O. Well, AS should only intentionally delay when it has competing threads fighting for the disk. For a single threaded io case like hdparm, it should never idle the drive. It never delays to increase merge rate, or anything like that - only to increase spatial locality on the drive for two or more processes accessing it simultanously. -- Jens Axboe