From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754537Ab2LLElr (ORCPT ); Tue, 11 Dec 2012 23:41:47 -0500 Received: from e28smtp02.in.ibm.com ([122.248.162.2]:59818 "EHLO e28smtp02.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754127Ab2LLElq (ORCPT ); Tue, 11 Dec 2012 23:41:46 -0500 Message-ID: <50C80ADF.8050504@linux.vnet.ibm.com> Date: Wed, 12 Dec 2012 10:11:03 +0530 From: Preeti U Murthy User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 MIME-Version: 1.0 To: Alex Shi CC: rob@landley.net, mingo@redhat.com, peterz@infradead.org, gregkh@linuxfoundation.org, andre.przywara@amd.com, rjw@sisk.pl, paul.gortmaker@windriver.com, akpm@linux-foundation.org, paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, pjt@google.com, vincent.guittot@linaro.org Subject: Re: [PATCH 08/18] sched: consider runnable load average in move_tasks References: <1355127754-8444-1-git-send-email-alex.shi@intel.com> <1355127754-8444-9-git-send-email-alex.shi@intel.com> In-Reply-To: <1355127754-8444-9-git-send-email-alex.shi@intel.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12121204-5816-0000-0000-000005CD8E01 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Alex, On 12/10/2012 01:52 PM, Alex Shi wrote: > Except using runnable load average in background, move_tasks is also > the key functions in load balance. We need consider the runnable load > average in it in order to the apple to apple load comparison. > > Signed-off-by: Alex Shi > --- > kernel/sched/fair.c | 11 ++++++++++- > 1 files changed, 10 insertions(+), 1 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 6d893a6..bbb069c 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -3741,6 +3741,15 @@ static unsigned long task_h_load(struct task_struct *p); > > static const unsigned int sched_nr_migrate_break = 32; > > +static unsigned long task_h_load_avg(struct task_struct *p) > +{ > + u32 period = p->se.avg.runnable_avg_period; > + if (!period) > + return 0; > + > + return task_h_load(p) * p->se.avg.runnable_avg_sum / period; ^^^^^^^^^^^^ This might result in an overflow,considering you are multiplying two 32 bit integers.Below is how this is handled in __update_task_entity_contrib in kernel/sched/fair.c u32 contrib; /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */ contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight); contrib /= (se->avg.runnable_avg_period + 1); se->avg.load_avg_contrib = scale_load(contrib); Also why can't p->se.load_avg_contrib be used directly? as a return value for task_h_load_avg? since this is already updated in update_task_entity_contrib and update_group_entity_contrib. > +} > + > /* > * move_tasks tries to move up to imbalance weighted load from busiest to > * this_rq, as part of a balancing operation within domain "sd". > @@ -3776,7 +3785,7 @@ static int move_tasks(struct lb_env *env) > if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu)) > goto next; > > - load = task_h_load(p); > + load = task_h_load_avg(p); > > if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) > goto next; > Regards Preeti U Murthy