From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933057AbdBHIwl (ORCPT ); Wed, 8 Feb 2017 03:52:41 -0500 Received: from mail-lf0-f68.google.com ([209.85.215.68]:33025 "EHLO mail-lf0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753478AbdBHIvd (ORCPT ); Wed, 8 Feb 2017 03:51:33 -0500 From: Uladzislau Rezki To: Ingo Molnar Cc: LKML , Peter Zijlstra , Uladzislau 2 Rezki Subject: [RFC,v2 3/3] sched: ignore task_h_load for CPU_NEWLY_IDLE Date: Wed, 8 Feb 2017 09:43:29 +0100 Message-Id: <1486543409-11493-3-git-send-email-urezki@gmail.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1486543409-11493-1-git-send-email-urezki@gmail.com> References: <1486543409-11493-1-git-send-email-urezki@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Uladzislau 2 Rezki A load balancer calculates imbalance factor for particular shed domain and tries to steal up the prescribed amount of weighted load. However, a small imbalance factor would sometimes prevent us from stealing any tasks at all. When a CPU is newly idle, it should steal first task which passes a migration criteria. Signed-off-by: Uladzislau 2 Rezki --- kernel/sched/fair.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 232ef3c..29e0d7f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6802,6 +6802,14 @@ static int detach_tasks(struct lb_env *env) if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1) break; + /* + * Another CPU can place tasks, since we do not hold dst_rq lock + * while doing balancing. If newly idle CPU already got something, + * give up to reduce latency. + */ + if (env->idle == CPU_NEWLY_IDLE && env->dst_rq->nr_running > 0) + break; + p = list_first_entry(tasks, struct task_struct, se.group_node); env->loop++; @@ -6824,8 +6832,9 @@ static int detach_tasks(struct lb_env *env) if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) goto next; - if ((load / 2) > env->imbalance) - goto next; + if (env->idle != CPU_NEWLY_IDLE) + if ((load / 2) > env->imbalance) + goto next; detach_task(p, env); list_add(&p->se.group_node, &env->tasks); -- 2.1.4