From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757264AbaIIPA5 (ORCPT ); Tue, 9 Sep 2014 11:00:57 -0400 Received: from terminus.zytor.com ([198.137.202.10]:41081 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757172AbaIIOyB (ORCPT ); Tue, 9 Sep 2014 10:54:01 -0400 Date: Tue, 9 Sep 2014 07:52:38 -0700 From: tip-bot for Jason Low Message-ID: Cc: linux-kernel@vger.kernel.org, bsegall@google.com, hpa@zytor.com, mingo@kernel.org, torvalds@linux-foundation.org, pjt@google.com, peterz@infradead.org, tim.c.chen@linux.intel.com, yuyang.du@intel.com, jason.low2@hp.com, Waiman.Long@hp.com, chegu_vinod@hp.com, tglx@linutronix.de, scott.norton@hp.com, aswin@hp.com Reply-To: mingo@kernel.org, hpa@zytor.com, bsegall@google.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, pjt@google.com, yuyang.du@intel.com, tim.c.chen@linux.intel.com, jason.low2@hp.com, Waiman.Long@hp.com, chegu_vinod@hp.com, tglx@linutronix.de, scott.norton@hp.com, aswin@hp.com In-Reply-To: <1409643684.19197.15.camel@j-VirtualBox> References: <1409643684.19197.15.camel@j-VirtualBox> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched: Reduce contention in update_cfs_rq_blocked_load() Git-Commit-ID: 8236d907ab3411ad452280faa8b26c1347327380 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: 8236d907ab3411ad452280faa8b26c1347327380 Gitweb: http://git.kernel.org/tip/8236d907ab3411ad452280faa8b26c1347327380 Author: Jason Low AuthorDate: Tue, 2 Sep 2014 00:41:24 -0700 Committer: Ingo Molnar CommitDate: Tue, 9 Sep 2014 06:47:29 +0200 sched: Reduce contention in update_cfs_rq_blocked_load() When running workloads on 2+ socket systems, based on perf profiles, the update_cfs_rq_blocked_load() function often shows up as taking up a noticeable % of run time. Much of the contention is in __update_cfs_rq_tg_load_contrib() when we update the tg load contribution stats. However, it turns out that in many cases, they don't need to be updated and "tg_contrib" is 0. This patch adds a check in __update_cfs_rq_tg_load_contrib() to skip updating tg load contribution stats when nothing needs to be updated. This reduces the cacheline contention that would be unnecessary. Reviewed-by: Ben Segall Reviewed-by: Waiman Long Signed-off-by: Jason Low Signed-off-by: Peter Zijlstra Cc: Paul Turner Cc: jason.low2@hp.com Cc: Yuyang Du Cc: Aswin Chandramouleeswaran Cc: Chegu Vinod Cc: Scott J Norton Cc: Tim Chen Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1409643684.19197.15.camel@j-VirtualBox Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 50d2025..be9e97b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2382,6 +2382,9 @@ static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq, tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg; tg_contrib -= cfs_rq->tg_load_contrib; + if (!tg_contrib) + return; + if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) { atomic_long_add(tg_contrib, &tg->load_avg); cfs_rq->tg_load_contrib += tg_contrib;