From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750832Ab0GaEB1 (ORCPT ); Sat, 31 Jul 2010 00:01:27 -0400 Received: from mailout-de.gmx.net ([213.165.64.22]:60752 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with SMTP id S1750709Ab0GaEB0 (ORCPT ); Sat, 31 Jul 2010 00:01:26 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX193cZRdAwZ3MZpT73Vo1ZaXmkJ2R0KzMH2dCM68Nm s4dwAYT76ZMx1J Subject: Re: Regression (bisected): Lots of wakeups when using battery From: Mike Galbraith To: Jaime Velasco Juan Cc: a.p.zijlstra@hello.nl, linux-kernel@vger.kernel.org, Thomas Gleixner In-Reply-To: <20100730214523.GA5571@pogo> References: <20100730214523.GA5571@pogo> Content-Type: text/plain Date: Sat, 31 Jul 2010 06:01:42 +0200 Message-Id: <1280548902.9686.51.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1.1 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (corrects cc) On Fri, 2010-07-30 at 22:45 +0100, Jaime Velasco Juan wrote: > Hi, testing 2.6.35-rc5 I noticed that when my laptop is on battery, > there are bursts of wakeups (they seem random, but usually happens once > each 5 sec. or so; they cause some audible noise). If the laptop is plugged > it behaves well. In single user mode, there are usually 2 wakeups/sec with > the system idle, but on battery an with the bug, it goes to more than 100 w/s. > > Bisection points to: > > commit 3310d4d38fbc514e7b18bd3b1eea8effdd63b5aa > Author: Peter Zijlstra > Date: Thu Jun 17 18:02:37 2010 +0200 > > nohz: Fix nohz ratelimit > > Chris Wedgwood reports that 39c0cbe (sched: Rate-limit nohz) causes a > serial console regression, unresponsiveness, and indeed it does. The > reason is that the nohz code is skipped even when the tick was already > stopped before the nohz_ratelimit(cpu) condition changed. > > Move the nohz_ratelimit() check to the other conditions which prevent > long idle sleeps. > > Reverting said commit seems to fix the issue. And if you revert that, using a serial console becomes.. unpleasant. The whole ratelimit nohz thing has been dropped for now. It's a nice little optimization for high frequency switchers on an underutilized box, but has caused more irritation than it's worth. -Mike