Return-path: Received: from casper.infradead.org ([85.118.1.10]:48954 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751437AbZJEOYk (ORCPT ); Mon, 5 Oct 2009 10:24:40 -0400 Date: Mon, 5 Oct 2009 07:24:28 -0700 From: Arjan van de Ven To: Frans Pop Cc: Linux Kernel Mailing List , Ingo Molnar , Peter Zijlstra , linux-wireless@vger.kernel.org Subject: Re: [.32-rc3] scheduler: iwlagn consistently high in "waiting for CPU" Message-ID: <20091005072428.16ce40e4@infradead.org> In-Reply-To: <200910051613.32631.elendil@planet.nl> References: <200910051500.55875.elendil@planet.nl> <200910051613.32631.elendil@planet.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-wireless-owner@vger.kernel.org List-ID: On Mon, 5 Oct 2009 16:13:31 +0200 Frans Pop wrote: > On Monday 05 October 2009, Frans Pop wrote: > > With .32-rc3 I'm getting occasional skips from amarok while playing > > music from an NFS share (3 today so far), something I've not had in > > a long time. > > > > The reason looks to be that latencytop consistently shows 'iwlagn' > > as the top affected process with "Scheduler: waiting for CPU". > > Values of 100-140 ms occur frequently, but I've also seen higher > > values (180, 207). I don't remember seeing iwlagn high in the list > > before, but I have not checked earlier kernels yet. > > > > Added to that 'phy0' also frequently shows high with values of > > 25-75 ms. > > > > The system is otherwise essentially idle. Other processes typically > > show a latency < 5 ms. > > If I give the system some work to do (like compiling a kernel), the > latencies on iwlagn and phy0 disappear (values < 5 ms). > Is this related to ondemand frequency scaling? shouldn't be.... but can you do a 5 second or so timechart recording of this? That will capture all scheduler delays as well as the P states etc.... (to do a timechart recording, first make sure debugfs is mounted, and then do in tools/perf ./perf timechart record sleep 5 then you can turn it into an SVG with ./perf timechart ) -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org