From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262491AbTLOCyY (ORCPT ); Sun, 14 Dec 2003 21:54:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263019AbTLOCyY (ORCPT ); Sun, 14 Dec 2003 21:54:24 -0500 Received: from mail-04.iinet.net.au ([203.59.3.36]:35769 "HELO mail.iinet.net.au") by vger.kernel.org with SMTP id S262491AbTLOCyX (ORCPT ); Sun, 14 Dec 2003 21:54:23 -0500 Message-ID: <3FDD205A.6040807@cyberone.com.au> Date: Mon, 15 Dec 2003 13:45:46 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030827 Debian/1.4-3 X-Accept-Language: en MIME-Version: 1.0 To: Guillaume Foliard CC: linux-kernel@vger.kernel.org, george anzinger Subject: Re: Scheduler degradation since 2.5.66 References: <200312142048.51579.guifo@wanadoo.fr> In-Reply-To: <200312142048.51579.guifo@wanadoo.fr> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Guillaume Foliard wrote: >Hello, > >I have been playing with kernel 2.5/2.6 for around 6 months now. I was quite >pleased with 2.5.65 to see that the soft real-time behaviour was much better >than 2.4.x. Since then I tried most of the 2.5/2.6 versions. But recently >someone warned me about some degradations with 2.6.0-test6. To show the >degradation since 2.5.66 I have run a simple test program on most of the >versions. This simple program is measuring the time it takes to a process to >be woken up after a call to nanosleep. >As the results are plots, please visit this small website for more >information : http://perso.wanadoo.fr/kayakgabon/linux >I'm ready to perform more tests or provide more information if necessary. > This isn't a problem with the scheduler, its a problem with sys_nanosleep. jiffies_to_timespec( {1000000us} ) returns 2 jiffies, and nanosleep adds an extra one and asks to sleep for that long (ie. 3ms). The more erratic timings could be due to interactivity changes as you say, but you probably aren't running without RT priority