From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754502Ab0DAInU (ORCPT ); Thu, 1 Apr 2010 04:43:20 -0400 Received: from metis.ext.pengutronix.de ([92.198.50.35]:40138 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754331Ab0DAInN (ORCPT ); Thu, 1 Apr 2010 04:43:13 -0400 Date: Thu, 1 Apr 2010 10:43:11 +0200 From: Michael Grzeschik To: Mike Galbraith Cc: linux-kernel@vger.kernel.org, rsc@pengutronix.de Subject: Re: Issues with Patch: "sched: Improve latencies and throughput" Message-ID: <20100401084311.GL10342@pengutronix.de> References: <20100331223106.GJ10342@pengutronix.de> <1270100986.6707.156.camel@marge.simson.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1270100986.6707.156.camel@marge.simson.net> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 10:25:29 up 11 days, 21:15, 30 users, load average: 0.95, 0.77, 0.95 User-Agent: Mutt/1.5.18 (2008-05-17) X-SA-Exim-Connect-IP: 2001:6f8:1178:2:215:17ff:fe12:23b0 X-SA-Exim-Mail-From: mgr@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 01, 2010 at 07:49:46AM +0200, Mike Galbraith wrote: > On Thu, 2010-04-01 at 00:31 +0200, Michael Grzeschik wrote: > > We are using an arm mx31 embedded cpu with the v2.6.34 Kernelrelease and > > realized some issues with the scheduling behaviour the patch "sched: > > Improve latencies and throughput" [1] by Mike Galbraith introduced to > > the kernel. > > > > When we used the alsa utility aplay to pipe some audio through an > > usbaudio device and put some scheduling overhead on the device, the > > amount of underruns, due to the not fast enough refilled ring buffer, > > was noticable increased with that patch [1] applied. Until we reverse > > applied the patch the amount of underruns was appreciable lower. > > Testcase? What we did was: # Copy some audiofile to /dev/shm $ cp audiofile.wav /dev/shm # Play that file with aplay in background $ aplay /dev/shm/auduifile.wav & # Put some scheduling load on the system $ hackbench 6 We did use this on an MX31 from Freescale running with about 500 MHz and the generic usbaudio driver to play the audio throgh an C-Media USB audiodongle. Expected results with that patch: underrun!!! (at least 323.946 ms long) < -- aplay underrun!!! (at least 59.477 ms long) < -- " underrun!!! (at least 194.873 ms long) < -- " Time: 7.048 < -- hackbench Time: 6.841 < -- " underrun!!! (at least 115.456 ms long) < -- aplay underrun!!! (at least 37.849 ms long) < -- " underrun!!! (at least 588.637 ms long) < -- " Time: 7.23 < -- hackbench results without the patch: Time: 3.728 < -- hackbench underrun!!! (at least 58.557 ms long) < -- aplay Time: 3.771 < -- hackbench underrun!!! (at least 97.538 ms long) < -- aplay Time: 3.732 < -- hackbench Time: 3.630 < -- .... Time: 3.636 Time: 3.643 Thanks, mgr -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |