From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751516Ab2LLG3B (ORCPT ); Wed, 12 Dec 2012 01:29:01 -0500 Received: from mga02.intel.com ([134.134.136.20]:29575 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750864Ab2LLG3A (ORCPT ); Wed, 12 Dec 2012 01:29:00 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,264,1355126400"; d="scan'208";a="232639913" Message-ID: <50C823A4.109@intel.com> Date: Wed, 12 Dec 2012 14:26:44 +0800 From: Alex Shi User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120912 Thunderbird/15.0.1 MIME-Version: 1.0 To: Preeti U Murthy 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> <50C80ADF.8050504@linux.vnet.ibm.com> In-Reply-To: <50C80ADF.8050504@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/12/2012 12:41 PM, Preeti U Murthy wrote: > 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); scale_load_down is do nothing. > > 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. No, only non task entity goes to update_group_entity_contrib. not task entity. >> +} >> + >> /* >> * 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 >