From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265487AbTFMSwl (ORCPT ); Fri, 13 Jun 2003 14:52:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265489AbTFMSwl (ORCPT ); Fri, 13 Jun 2003 14:52:41 -0400 Received: from e5.ny.us.ibm.com ([32.97.182.105]:58752 "EHLO e5.ny.us.ibm.com") by vger.kernel.org with ESMTP id S265487AbTFMSwk (ORCPT ); Fri, 13 Jun 2003 14:52:40 -0400 Date: Fri, 13 Jun 2003 12:02:10 -0700 From: Patrick Mansfield To: Steven Dake Cc: Patrick Mochel , Oliver Neukum , linux-kernel@vger.kernel.org Subject: Re: [PATCH] udev enhancements to use kernel event queue Message-ID: <20030613120210.A23314@beaverton.ibm.com> References: <3EEA0577.8050200@mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <3EEA0577.8050200@mvista.com>; from sdake@mvista.com on Fri, Jun 13, 2003 at 10:10:15AM -0700 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 13, 2003 at 10:10:15AM -0700, Steven Dake wrote: > I propose the following test: > Create 3 partitions on all 50 disks. Create system to boot kernel.org > 2.5.70 with initramdisk. Try greg's original udev without kernel aptch, > try modified udev with kernel patch, time each system's startup time. > > Do you agree with the test methodology? If so, then we can proceed with > gathering real data. I've seen a large variance on detect/probe/scan for fibre disks depending on whether the feral or qlogic drive is used. This is with switch attached fibre storage. The qlogic takes more time to probe, but has shorter timeouts when trying to detect disabled or disconnected ports. On my system (where I have a few unconnected fibre cards), the insmod of the qlogic and feral seem to be about equal (I haven't timed the actual differences, I normally don't build a kernel or modules with both feral and qlogic available, they are both available only outside of the mainline kernel). If I removed or connected the unconnected cards, the feral driver would be faster. You could probably improve boot time (or modprobe time) more by speeding up the qlogic driver or using the feral driver rather than trying to speed up the hotplug/whatever. Note that scsi_debug driver has a default IO response time of 1 tick (scsi_debug_delay), you can set it to zero, but then it has to wakeup the softirqd to complete the IO. So you you either rely on a timeout to complete an IO, or a wakeup of the ksoftirqd. I was trying to measure IO latencies at one point using scsi_debug, but I seemed to end up measuring context switch times instead. -- Patrick Mansfield