Return-path: Received: from mail.gmx.net ([213.165.64.20]:52346 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S932435AbZJHOzn (ORCPT ); Thu, 8 Oct 2009 10:55:43 -0400 Subject: Re: [.32-rc3] scheduler: iwlagn consistently high in "waiting for CPU" From: Mike Galbraith To: Arjan van de Ven Cc: Frans Pop , Linux Kernel Mailing List , Ingo Molnar , Peter Zijlstra , linux-wireless@vger.kernel.org In-Reply-To: <1255011186.7294.1.camel@marge.simson.net> References: <200910051500.55875.elendil@planet.nl> <200910061749.02805.elendil@planet.nl> <200910071910.53907.elendil@planet.nl> <200910072034.57511.elendil@planet.nl> <1254974743.7797.21.camel@marge.simson.net> <20091008064041.67219b13@infradead.org> <1255011186.7294.1.camel@marge.simson.net> Content-Type: text/plain Date: Thu, 08 Oct 2009 16:54:54 +0200 Message-Id: <1255013694.7309.7.camel@marge.simson.net> Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Thu, 2009-10-08 at 16:13 +0200, Mike Galbraith wrote: > On Thu, 2009-10-08 at 06:40 -0700, Arjan van de Ven wrote: > > On Thu, 08 Oct 2009 06:05:43 +0200 > > Mike Galbraith wrote: > > > > OK, I see latencytop spikes here on an idle box too, to the tune of up > > > to a _second_. Booting with nohz=off seems to have cured it. > > > > interesting.. > > > > > > by chance, does this patch fix it ? > > I haven't seen incredible yet, but with idle box, have seen > 200ms, so > would say no. But this dinky hunk of my patchlet does indeed still fix it right up. Index: linux-2.6/kernel/sched_fair.c =================================================================== --- linux-2.6.orig/kernel/sched_fair.c +++ linux-2.6/kernel/sched_fair.c @@ -495,8 +495,10 @@ static void update_curr(struct cfs_rq *c u64 now = rq_of(cfs_rq)->clock; unsigned long delta_exec; - if (unlikely(!curr)) + if (unlikely(!curr)) { + update_rq_clock(rq_of(cfs_rq)); return; + } /* * Get the amount of time the current task was running We have a clock problem with NO_HZ coming out of idle, so we may well have real latency issues at the same time, not bogons. -Mike