Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932783Ab1BPB5C (ORCPT ); Tue, 15 Feb 2011 20:57:02 -0500 Received: from kroah.org ([198.145.64.141]:49247 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758579Ab1BPBvj (ORCPT ); Tue, 15 Feb 2011 20:51:39 -0500 X-Mailbox-Line: From gregkh@clark.kroah.org Tue Feb 15 17:47:03 2011 Message-Id: <20110216014703.742949985@clark.kroah.org> User-Agent: quilt/0.48-11.2 Date: Tue, 15 Feb 2011 17:46:01 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Nikhil Rao , Peter Zijlstra , Ingo Molnar , Mike Galbraith Subject: [095/115] sched: Set group_imb only a task can be pulled from the busiest cpu In-Reply-To: <20110216014741.GA24678@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2814 Lines: 77 2.6.32-longterm review patch. If anyone has any objections, please let us know. ------------------ Commit: 2582f0eba54066b5e98ff2b27ef0cfa833b59f54 upstream 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 Signed-off-by: Peter Zijlstra LKML-Reference: <1286996978-7007-3-git-send-email-ncrao@google.com> [ small code readability edits ] Signed-off-by: Ingo Molnar Signed-off-by: Mike Galbraith Acked-by: Peter Zijlstra Signed-off-by: Greg Kroah-Hartman --- kernel/sched.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3745,7 +3745,7 @@ static inline void update_sg_lb_stats(st 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; @@ -3759,6 +3759,7 @@ static inline void update_sg_lb_stats(st /* 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); @@ -3776,8 +3777,10 @@ static inline void update_sg_lb_stats(st 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; } @@ -3815,11 +3818,10 @@ static inline void update_sg_lb_stats(st 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 = - DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE); + sgs->group_capacity = DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE); } /** -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/