From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754540AbaEHKpk (ORCPT ); Thu, 8 May 2014 06:45:40 -0400 Received: from terminus.zytor.com ([198.137.202.10]:33322 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753324AbaEHKpg (ORCPT ); Thu, 8 May 2014 06:45:36 -0400 Date: Thu, 8 May 2014 03:44:33 -0700 From: tip-bot for Jason Low Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, jason.low2@hp.com, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, tglx@linutronix.de, jason.low2@hp.com In-Reply-To: <1398303035-18255-4-git-send-email-jason.low2@hp.com> References: <1398303035-18255-4-git-send-email-jason.low2@hp.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/fair: Stop searching for tasks in newidle balance if there are runnable tasks Git-Commit-ID: 39a4d9ca77a31503c6317e49742341d0859d5cb2 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 39a4d9ca77a31503c6317e49742341d0859d5cb2 Gitweb: http://git.kernel.org/tip/39a4d9ca77a31503c6317e49742341d0859d5cb2 Author: Jason Low AuthorDate: Wed, 23 Apr 2014 18:30:35 -0700 Committer: Ingo Molnar CommitDate: Wed, 7 May 2014 13:33:53 +0200 sched/fair: Stop searching for tasks in newidle balance if there are runnable tasks It was found that when running some workloads (such as AIM7) on large systems with many cores, CPUs do not remain idle for long. Thus, tasks can wake/get enqueued while doing idle balancing. In this patch, while traversing the domains in idle balance, in addition to checking for pulled_task, we add an extra check for this_rq->nr_running for determining if we should stop searching for tasks to pull. If there are runnable tasks on this rq, then we will stop traversing the domains. This reduces the chance that idle balance delays a task from running. This patch resulted in approximately a 6% performance improvement when running a Java Server workload on an 8 socket machine. Signed-off-by: Jason Low Signed-off-by: Peter Zijlstra Cc: Linus Torvalds Cc: daniel.lezcano@linaro.org Cc: alex.shi@linaro.org Cc: preeti@linux.vnet.ibm.com Cc: efault@gmx.de Cc: vincent.guittot@linaro.org Cc: morten.rasmussen@arm.com Cc: aswin@hp.com Cc: chegu_vinod@hp.com Link: http://lkml.kernel.org/r/1398303035-18255-4-git-send-email-jason.low2@hp.com Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 051903f..28ccf50 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6713,7 +6713,6 @@ static int idle_balance(struct rq *this_rq) if (sd->flags & SD_BALANCE_NEWIDLE) { t0 = sched_clock_cpu(this_cpu); - /* If we've pulled tasks over stop searching: */ pulled_task = load_balance(this_cpu, this_rq, sd, CPU_NEWLY_IDLE, &continue_balancing); @@ -6728,7 +6727,12 @@ static int idle_balance(struct rq *this_rq) interval = msecs_to_jiffies(sd->balance_interval); if (time_after(next_balance, sd->last_balance + interval)) next_balance = sd->last_balance + interval; - if (pulled_task) + + /* + * Stop searching for tasks to pull if there are + * now runnable tasks on this rq. + */ + if (pulled_task || this_rq->nr_running > 0) break; } rcu_read_unlock();