From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760334Ab0I1AaW (ORCPT ); Mon, 27 Sep 2010 20:30:22 -0400 Received: from smtp-out.google.com ([74.125.121.35]:63252 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760181Ab0I1AaV (ORCPT ); Mon, 27 Sep 2010 20:30:21 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=wJaQD4LF49rlKOCC9i92P7zvaVOzMc0z4u6GOwSb/nDHaKvkrBe7R+YMEbknxwB4J RSxQGZl2AIXPvvEI8DELA== From: Nikhil Rao To: Ingo Molnar , Peter Zijlstra , Mike Galbraith Cc: Venkatesh Pallipadi , linux-kernel@vger.kernel.org, Nikhil Rao Subject: [PATCH 1/3] sched: set group_imb only a task can be pulled from the busiest cpu Date: Mon, 27 Sep 2010 17:29:56 -0700 Message-Id: <1285633798-26886-2-git-send-email-ncrao@google.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1285633798-26886-1-git-send-email-ncrao@google.com> References: <1285633798-26886-1-git-send-email-ncrao@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When cycling through sched groups to determine the busiest group, set group_imb only if the busiest cpu has more than 1 runnable task. This patch fixes the case where two cpus in a group have one runnable task each, but there is a large weight differential between these two tasks. The load balancer is unable to migrate any task from this group, and hence do not consider this group to be imbalanced. Signed-off-by: Nikhil Rao --- kernel/sched_fair.c | 10 +++++++--- 1 files changed, 7 insertions(+), 3 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index a171138..de8a6a0 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -2378,7 +2378,7 @@ static inline void update_sg_lb_stats(struct sched_domain *sd, int local_group, const struct cpumask *cpus, int *balance, struct sg_lb_stats *sgs) { - unsigned long load, max_cpu_load, min_cpu_load; + unsigned long load, max_cpu_load, min_cpu_load, max_nr_running; int i; unsigned int balance_cpu = -1, first_idle_cpu = 0; unsigned long avg_load_per_task = 0; @@ -2389,6 +2389,7 @@ static inline void update_sg_lb_stats(struct sched_domain *sd, /* Tally up the load of all CPUs in the group */ max_cpu_load = 0; min_cpu_load = ~0UL; + max_nr_running = 0; for_each_cpu_and(i, sched_group_cpus(group), cpus) { struct rq *rq = cpu_rq(i); @@ -2406,8 +2407,10 @@ static inline void update_sg_lb_stats(struct sched_domain *sd, load = target_load(i, load_idx); } else { load = source_load(i, load_idx); - if (load > max_cpu_load) + if (load > max_cpu_load) { max_cpu_load = load; + max_nr_running = rq->nr_running; + } if (min_cpu_load > load) min_cpu_load = load; } @@ -2447,7 +2450,8 @@ static inline void update_sg_lb_stats(struct sched_domain *sd, if (sgs->sum_nr_running) avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running; - if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task) + if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task && + max_nr_running > 1) sgs->group_imb = 1; sgs->group_capacity = -- 1.7.1