Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267356AbUIATIn (ORCPT ); Wed, 1 Sep 2004 15:08:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267415AbUIATIn (ORCPT ); Wed, 1 Sep 2004 15:08:43 -0400 Received: from viper.oldcity.dca.net ([216.158.38.4]:26082 "HELO viper.oldcity.dca.net") by vger.kernel.org with SMTP id S267356AbUIATIh (ORCPT ); Wed, 1 Sep 2004 15:08:37 -0400 Subject: Re: [PATCH] Configure IDE probe delays From: Lee Revell To: Alan Cox Cc: Mark Lord , bzolnier@milosz.na.pl, Greg Stark , Denis Vlasenko , Todd Poynor , Linux Kernel Mailing List , tim.bird@am.sony.com, dsingleton@mvista.com In-Reply-To: <1094051215.2777.15.camel@localhost.localdomain> References: <20040730191100.GA22201@slurryseal.ddns.mvista.com> <200408272005.08407.bzolnier@elka.pw.edu.pl> <1093630121.837.39.camel@krustophenia.net> <200408272059.51779.bzolnier@elka.pw.edu.pl> <4135CC9E.5060905@rtr.ca> <1094051215.2777.15.camel@localhost.localdomain> Content-Type: text/plain Message-Id: <1094065718.1970.39.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Wed, 01 Sep 2004 15:08:39 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1279 Lines: 30 On Wed, 2004-09-01 at 11:06, Alan Cox wrote: > On Mer, 2004-09-01 at 14:20, Mark Lord wrote: > > LBA48 is only needed when (1) the sector count is greater than 256, > > and/or (2) the ending sector number >= (1<<28). > > I've played with this a bit and in the -ac IDE code it can drop back > to LBA28 for devices that are small enough not to need LBA48 when the > controller only supports PIO for LBA48 modes (eg some ALi) as 2.4-ac > did. > > > I regularly include this optimisation in the drivers I have been > > working on since LBA48 first appeared. > > It isn't always a win. You get cut down to 256 sectors per I/O which for > some workloads has a cost and you need to factor that into the command > issue choice as well as the last sector number being accessed. > I have never been able to measure a decrease in disk throughput in any disk benchmark with 256 sectors per I/O vs. 1024. This is a modestly powered desktop with a single drive though. What kinds of workloads would you expect to be affected by this? Lee - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/