Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933385AbdCWKda (ORCPT ); Thu, 23 Mar 2017 06:33:30 -0400 Received: from LGEAMRELO12.lge.com ([156.147.23.52]:55457 "EHLO lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932757AbdCWKdW (ORCPT ); Thu, 23 Mar 2017 06:33:22 -0400 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 165.244.249.26 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com From: Byungchul Park To: , CC: , , , Subject: [PATCH 1/8] sched/deadline: Make find_later_rq() choose a closer cpu in topology Date: Thu, 23 Mar 2017 19:32:36 +0900 Message-ID: <1490265163-29981-2-git-send-email-byungchul.park@lge.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1490265163-29981-1-git-send-email-byungchul.park@lge.com> References: <1490265163-29981-1-git-send-email-byungchul.park@lge.com> X-MIMETrack: Itemize by SMTP Server on LGEKRMHUB06/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2017/03/23 19:33:18, Serialize by Router on LGEKRMHUB06/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2017/03/23 19:33:18, Serialize complete at 2017/03/23 19:33:18 MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3277 Lines: 105 When cpudl_find() returns any among free_cpus, the cpu might not be closer than others, considering sched domain. For example: this_cpu: 15 free_cpus: 0, 1,..., 14 (== later_mask) best_cpu: 0 topology: 0 --+ +--+ 1 --+ | +-- ... --+ 2 --+ | | +--+ | 3 --+ | ... ... 12 --+ | +--+ | 13 --+ | | +-- ... -+ 14 --+ | +--+ 15 --+ In this case, it would be best to select 14 since it's a free cpu and closest to 15(this_cpu). However, currently the code select 0(best_cpu) even though that's just any among free_cpus. Fix it. Signed-off-by: Byungchul Park --- kernel/sched/deadline.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index a2ce590..49c93b9 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1324,7 +1324,7 @@ static int find_later_rq(struct task_struct *task) struct sched_domain *sd; struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl); int this_cpu = smp_processor_id(); - int best_cpu, cpu = task_cpu(task); + int cpu = task_cpu(task); /* Make sure the mask is initialized first */ if (unlikely(!later_mask)) @@ -1337,17 +1337,14 @@ static int find_later_rq(struct task_struct *task) * We have to consider system topology and task affinity * first, then we can look for a suitable cpu. */ - best_cpu = cpudl_find(&task_rq(task)->rd->cpudl, - task, later_mask); - if (best_cpu == -1) + if (cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask) == -1) return -1; /* - * If we are here, some target has been found, - * the most suitable of which is cached in best_cpu. - * This is, among the runqueues where the current tasks - * have later deadlines than the task's one, the rq - * with the latest possible one. + * If we are here, some targets have been found, including + * the most suitable which is, among the runqueues where the + * current tasks have later deadlines than the task's one, the + * rq with the latest possible one. * * Now we check how well this matches with task's * affinity and system topology. @@ -1367,6 +1364,7 @@ static int find_later_rq(struct task_struct *task) rcu_read_lock(); for_each_domain(cpu, sd) { if (sd->flags & SD_WAKE_AFFINE) { + int closest_cpu; /* * If possible, preempting this_cpu is @@ -1378,14 +1376,17 @@ static int find_later_rq(struct task_struct *task) return this_cpu; } + closest_cpu = cpumask_first_and(later_mask, + sched_domain_span(sd)); /* - * Last chance: if best_cpu is valid and is - * in the mask, that becomes our choice. + * Last chance: if a cpu being in both later_mask + * and current sd span is valid, that becomes our + * choice. Of course, the latest possible cpu is + * already under consideration through later_mask. */ - if (best_cpu < nr_cpu_ids && - cpumask_test_cpu(best_cpu, sched_domain_span(sd))) { + if (closest_cpu < nr_cpu_ids) { rcu_read_unlock(); - return best_cpu; + return closest_cpu; } } } -- 1.9.1