Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754290AbdGNNVU (ORCPT ); Fri, 14 Jul 2017 09:21:20 -0400 Received: from mail-yw0-f195.google.com ([209.85.161.195]:35401 "EHLO mail-yw0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754230AbdGNNVS (ORCPT ); Fri, 14 Jul 2017 09:21:18 -0400 From: Josef Bacik To: mingo@redhat.com, peterz@infradead.org, linux-kernel@vger.kernel.org, umgwanakikbuti@gmail.com, tj@kernel.org, kernel-team@fb.com Cc: Josef Bacik Subject: [PATCH 7/7] sched/fair: don't wake affine recently load balanced tasks Date: Fri, 14 Jul 2017 13:21:04 +0000 Message-Id: <1500038464-8742-8-git-send-email-josef@toxicpanda.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1500038464-8742-1-git-send-email-josef@toxicpanda.com> References: <1500038464-8742-1-git-send-email-josef@toxicpanda.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1963 Lines: 58 From: Josef Bacik The wake affinity logic will move tasks between two cpu's that appear to be loaded equally at the current time, with a slight bias towards cache locality. However on a heavily loaded system the load balancer has a better insight into what needs to be moved around, so instead keep track of the last time a task was migrated by the load balancer. If it was recent, opt to let the process stay on it's current CPU (or an idle sibling). Signed-off-by: Josef Bacik --- include/linux/sched.h | 1 + kernel/sched/fair.c | 11 +++++++++++ 2 files changed, 12 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index 1a0eadd..d872780 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -528,6 +528,7 @@ struct task_struct { unsigned long wakee_flip_decay_ts; struct task_struct *last_wakee; + unsigned long last_balance_ts; int wake_cpu; #endif int on_rq; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 034d5df..6a98a38 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5604,6 +5604,16 @@ static int wake_wide(struct task_struct *p) unsigned int slave = p->wakee_flips; int factor = this_cpu_read(sd_llc_size); + /* + * If we've balanced this task recently we don't want to undo all of + * that hard work by the load balancer and move it to the current cpu. + * Constantly overriding the load balancers decisions is going to make + * it question its purpose in life and give it anxiety and self worth + * issues, and nobody wants that. + */ + if (time_before(jiffies, p->last_balance_ts + HZ)) + return 1; + if (master < slave) swap(master, slave); if (slave < factor || master < slave * factor) @@ -7097,6 +7107,7 @@ static int detach_tasks(struct lb_env *env) goto next; detach_task(p, env); + p->last_balance_ts = jiffies; list_add(&p->se.group_node, &env->tasks); detached++; -- 2.9.3