From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755567AbcFQNQ6 (ORCPT ); Fri, 17 Jun 2016 09:16:58 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:59403 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752668AbcFQNQ4 (ORCPT ); Fri, 17 Jun 2016 09:16:56 -0400 X-IBM-Helo: d01dlp02.pok.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org;linux-pm@vger.kernel.org Date: Fri, 17 Jun 2016 06:16:51 -0700 From: "Paul E. McKenney" To: "Rafael J. Wysocki" Cc: Jisheng Zhang , Peter Zijlstra , "Rafael J. Wysocki" , Viresh Kumar , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List Subject: Re: regression caused by 08f511fd41c3 ("cpufreq: Reduce cpufreq_update_util() overhead a bit") Reply-To: paulmck@linux.vnet.ibm.com References: <20160617163023.5bb374f8@xhacker> <20160617164054.6339c5d4@xhacker> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16061713-0040-0000-0000-00000097BB98 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16061713-0041-0000-0000-000004719DE7 Message-Id: <20160617131651.GU3923@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-06-17_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1606170156 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 17, 2016 at 03:09:36PM +0200, Rafael J. Wysocki wrote: > On Fri, Jun 17, 2016 at 10:40 AM, Jisheng Zhang wrote: > > Dear all, > > > > On Fri, 17 Jun 2016 16:30:23 +0800 Jisheng Zhang wrote: > > > >> Dear all, > >> > >> I found one regression: In an idle system, wakeups/s (reported by powertop) > >> is increased a lot, e.g on a intel snb 4 core platform, the wakeup event > >> number is increased from 8 wakeups/s to 24 wakeup/s. bisect points to > >> this commit. I could send detailed bisect log if it's wanted. > >> > > > > more information maybe useful: after the commit, the top two wakeup source > > are > > > > Process [rcu_sched] > > > > Timer tick_sched_timer > > And what was there before the commit? > > Granted, I'm not seeing this on my systems. > > Paul, Peter, any ideas about what may be going on here? Looks to me like this commit moved some code from synchronize_rcu() to synchronize_sched(). Assuming that this is a CONFIG_PREEMPT=y system, might there have been a decrease in the wakeups from the rcu_preempt kthread? Thanx, Paul