Return-path: Received: from casper.infradead.org ([85.118.1.10]:36637 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932208AbZJHPJi (ORCPT ); Thu, 8 Oct 2009 11:09:38 -0400 Date: Thu, 8 Oct 2009 08:09:36 -0700 From: Arjan van de Ven To: Frans Pop Cc: Mike Galbraith , 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: <20091008080936.5f3b0e1b@infradead.org> In-Reply-To: <200910081655.37485.elendil@planet.nl> References: <200910051500.55875.elendil@planet.nl> <1254974743.7797.21.camel@marge.simson.net> <20091008064041.67219b13@infradead.org> <200910081655.37485.elendil@planet.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-wireless-owner@vger.kernel.org List-ID: On Thu, 8 Oct 2009 16:55:36 +0200 Frans Pop wrote: > > It turns out that on x86, these two 'opportunistic' timers only > > get checked when another "real" timer happens. > > These opportunistic timers have the objective to save power by > > hitchhiking on other wakeups, as to avoid CPU wakeups by themselves > > as much as possible. > > This patch makes quite a difference for me. iwlagn and phy0 now > consistently show at ~10 ms or lower.\ most excellent > I do still get occasional high latencies, but those are for things > like "[rpc_wait_bit_killable]" or "Writing a page to disk", where I > guess you'd expect them. Those high latencies are mostly only listed > for "Global" and don't translate to individual processes. and they're very different types of latencies, caused by disk and such. > The ~10 ms I still get for iwlagn and phy0 (and sometimes higher (~30 > ms) for others like Xorg and artsd) is still "Scheduler: waiting for > cpu'. If it is actually due to (un)interuptable sleep, isn't that a > misleading label? I directly associated that with scheduler latency. it's actually the time between wakeup and running, as measured by scheduler statistics -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org