From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934695Ab3BTGUI (ORCPT ); Wed, 20 Feb 2013 01:20:08 -0500 Received: from mga03.intel.com ([143.182.124.21]:45993 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934638Ab3BTGUH (ORCPT ); Wed, 20 Feb 2013 01:20:07 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,699,1355126400"; d="scan'208";a="259159818" Message-ID: <51246B1A.8040100@intel.com> Date: Wed, 20 Feb 2013 14:20:10 +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: Alex Shi CC: torvalds@linux-foundation.org, mingo@redhat.com, peterz@infradead.org, tglx@linutronix.de, akpm@linux-foundation.org, arjan@linux.intel.com, bp@alien8.de, pjt@google.com, namhyung@kernel.org, efault@gmx.de, vincent.guittot@linaro.org, gregkh@linuxfoundation.org, preeti@linux.vnet.ibm.com, viresh.kumar@linaro.org, linux-kernel@vger.kernel.org, morten.rasmussen@arm.com Subject: Re: [patch v5 02/15] sched: set initial load avg of new forked task References: <1361164062-20111-1-git-send-email-alex.shi@intel.com> <1361164062-20111-3-git-send-email-alex.shi@intel.com> In-Reply-To: <1361164062-20111-3-git-send-email-alex.shi@intel.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 02/18/2013 01:07 PM, Alex Shi wrote: > New task has no runnable sum at its first runnable time, so its > runnable load is zero. That makes burst forking balancing just select > few idle cpus to assign tasks if we engage runnable load in balancing. > > Set initial load avg of new forked task as its load weight to resolve > this issue. > patch answering PJT's update here. that merged the 1st and 2nd patches into one. other patches in serial don't need to change. ========= >>From 89b56f2e5a323a0cb91c98be15c94d34e8904098 Mon Sep 17 00:00:00 2001 From: Alex Shi Date: Mon, 3 Dec 2012 17:30:39 +0800 Subject: [PATCH 01/14] sched: set initial value of runnable avg for new forked task We need initialize the se.avg.{decay_count, load_avg_contrib} for a new forked task. Otherwise random values of above variables cause mess when do new task enqueue: enqueue_task_fair enqueue_entity enqueue_entity_load_avg and make forking balancing imbalance since incorrect load_avg_contrib. set avg.decay_count = 0, and avg.load_avg_contrib = se->load.weight to resolve such issues. Signed-off-by: Alex Shi --- kernel/sched/core.c | 3 +++ kernel/sched/fair.c | 4 ++++ 2 files changed, 7 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 26058d0..1452e14 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1559,6 +1559,7 @@ static void __sched_fork(struct task_struct *p) #if defined(CONFIG_SMP) && defined(CONFIG_FAIR_GROUP_SCHED) p->se.avg.runnable_avg_period = 0; p->se.avg.runnable_avg_sum = 0; + p->se.avg.decay_count = 0; #endif #ifdef CONFIG_SCHEDSTATS memset(&p->se.statistics, 0, sizeof(p->se.statistics)); @@ -1646,6 +1647,8 @@ void sched_fork(struct task_struct *p) p->sched_reset_on_fork = 0; } + p->se.avg.load_avg_contrib = p->se.load.weight; + if (!rt_prio(p->prio)) p->sched_class = &fair_sched_class; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 81fa536..cae5134 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1509,6 +1509,10 @@ static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq, * We track migrations using entity decay_count <= 0, on a wake-up * migration we use a negative decay count to track the remote decays * accumulated while sleeping. + * + * When enqueue a new forked task, the se->avg.decay_count == 0, so + * we bypass update_entity_load_avg(), use avg.load_avg_contrib initial + * value: se->load.weight. */ if (unlikely(se->avg.decay_count <= 0)) { se->avg.last_runnable_update = rq_of(cfs_rq)->clock_task; -- 1.7.12