From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265898AbUGTOSo (ORCPT ); Tue, 20 Jul 2004 10:18:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265900AbUGTOSo (ORCPT ); Tue, 20 Jul 2004 10:18:44 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:8892 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S265898AbUGTOSl (ORCPT ); Tue, 20 Jul 2004 10:18:41 -0400 Date: Tue, 20 Jul 2004 10:19:05 -0200 From: Jens Axboe To: Ingo Molnar Cc: Lee Revell , Andrew Morton , linux-audio-dev@music.columbia.edu, arjanv@redhat.com, linux-kernel Subject: Re: [linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch Message-ID: <20040720121905.GG1651@suse.de> References: <1089673014.10777.42.camel@mindpipe> <20040712163141.31ef1ad6.akpm@osdl.org> <1089677823.10777.64.camel@mindpipe> <20040712174639.38c7cf48.akpm@osdl.org> <1089687168.10777.126.camel@mindpipe> <20040712205917.47d1d58b.akpm@osdl.org> <1089705440.20381.14.camel@mindpipe> <20040719104837.GA9459@elte.hu> <1090301906.22521.16.camel@mindpipe> <20040720061227.GC27118@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040720061227.GC27118@elte.hu> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 20 2004, Ingo Molnar wrote: > > How much I/O do you allow to be in flight at once? It seems like by > > decreasing the maximum size of I/O that you handle in one interrupt > > you could improve this quite a bit. Disk throughput is good enough, > > anyone in the real world who would feel a 10% hit would just throw > > hardware at the problem. > > i'm not sure whether this particular value (max # of sg-entries per IO > op) is runtime tunable. Jens? Might make sense to enable elvtune-alike > tunability of this value. elvtune is long dead :-) it's not tweakable right now, but if you wish to experiment you just need to add a line to ide-disk.c:idedisk_setup() - pseudo patch: + blk_queue_max_sectors(drive->queue, 32); + printk("%s: max request size: %dKiB\n", drive->name, drive->queue->max_sectors / 2); /* Extract geometry if we did not already have one for the drive */ above will limit max request to 16kb, experiment as you see fit. -- Jens Axboe