From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760653AbZEGKum (ORCPT ); Thu, 7 May 2009 06:50:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752667AbZEGKuc (ORCPT ); Thu, 7 May 2009 06:50:32 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:60524 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752474AbZEGKub (ORCPT ); Thu, 7 May 2009 06:50:31 -0400 Date: Thu, 7 May 2009 12:50:07 +0200 From: Ingo Molnar To: KOSAKI Motohiro Cc: LKML , Bharata B Rao , Balaji Rao , Dhaval Giani , KAMEZAWA Hiroyuki , Peter Zijlstra , Balbir Singh , Martin Schwidefsky Subject: Re: [PATCH v3] cpuacct: VIRT_CPU_ACCOUNTING don't prevent percpu cputime count Message-ID: <20090507105007.GA28398@elte.hu> References: <20090507185831.9D24.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090507185831.9D24.A69D9226@jp.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * KOSAKI Motohiro wrote: > > Changelog: > since v2 > - revert using percpu_counter_sum() > > since v1 > - use percpu_counter_sum() instead percpu_counter_read() > > > ------------------------------------- > Subject: [PATCH v3] cpuacct: VIRT_CPU_ACCOUNTING don't prevent percpu cputime count > > cpuacct_update_stats() is called at every tick updating. and it use percpu_counter > for avoiding performance degression. > > For archs which define VIRT_CPU_ACCOUNTING, every tick would result > in >1000 units of cputime updates and since this is much much greater > than percpu_batch_counter, we end up taking spinlock on every tick. > > This patch change batch rule. now, any cpu can store "percpu_counter_bach * jiffies" > cputime in per-cpu cache. > it mean this patch don't have behavior change if VIRT_CPU_ACCOUNTING=n. > > Cc: Bharata B Rao > Cc: Balaji Rao > Cc: Dhaval Giani > Cc: KAMEZAWA Hiroyuki > Cc: Peter Zijlstra > Cc: Balbir Singh > Cc: Ingo Molnar > Cc: Martin Schwidefsky > Signed-off-by: KOSAKI Motohiro > --- > kernel/sched.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > Index: b/kernel/sched.c > =================================================================== > --- a/kernel/sched.c 2009-04-30 11:37:47.000000000 +0900 > +++ b/kernel/sched.c 2009-05-07 16:34:00.000000000 +0900 > @@ -10221,6 +10221,7 @@ struct cpuacct { > }; > > struct cgroup_subsys cpuacct_subsys; > +static s32 cpuacct_batch; should be __read_mostly i guess. > > /* return cpu accounting group corresponding to this container */ > static inline struct cpuacct *cgroup_ca(struct cgroup *cgrp) > @@ -10250,6 +10251,9 @@ static struct cgroup_subsys_state *cpuac > if (!ca->cpuusage) > goto out_free_ca; > > + if (!cpuacct_batch) > + cpuacct_batch = jiffies_to_cputime(percpu_counter_batch); So this is a once per boot condition? Why not initialize it in sched_init() or so? (instead of incuring this ugly check all the time) Ingo