Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751660AbdHRIWI (ORCPT ); Fri, 18 Aug 2017 04:22:08 -0400 Received: from LGEAMRELO13.lge.com ([156.147.23.53]:55789 "EHLO lgeamrelo13.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750810AbdHRIWF (ORCPT ); Fri, 18 Aug 2017 04:22:05 -0400 X-Original-SENDERIP: 156.147.1.125 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: peterz@infradead.org, mingo@kernel.org Cc: joel.opensrc@gmail.com, linux-kernel@vger.kernel.org, juri.lelli@gmail.com, rostedt@goodmis.org, kernel-team@lge.com Subject: [PATCH v8 2/2] sched/rt: Add support for SD_PREFER_SIBLING on find_lowest_rq() Date: Fri, 18 Aug 2017 17:21:59 +0900 Message-Id: <1503044519-2804-3-git-send-email-byungchul.park@lge.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1503044519-2804-1-git-send-email-byungchul.park@lge.com> References: <1503044519-2804-1-git-send-email-byungchul.park@lge.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2766 Lines: 97 It would be better to try to check other siblings first if SD_PREFER_SIBLING is flaged when pushing tasks - migration. Signed-off-by: Byungchul Park --- kernel/sched/rt.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 53 insertions(+), 3 deletions(-) diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 979b734..b6d8ba9 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1618,12 +1618,35 @@ static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu) static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask); +/* + * Find the first cpu in: mask & sd & ~prefer + */ +static int find_cpu(const struct cpumask *mask, + const struct sched_domain *sd, + const struct sched_domain *prefer) +{ + const struct cpumask *sds = sched_domain_span(sd); + const struct cpumask *ps = prefer ? sched_domain_span(prefer) : NULL; + int cpu; + + for_each_cpu(cpu, mask) { + if (!cpumask_test_cpu(cpu, sds)) + continue; + if (ps && cpumask_test_cpu(cpu, ps)) + continue; + break; + } + + return cpu; +} + static int find_lowest_rq(struct task_struct *task) { - struct sched_domain *sd; + struct sched_domain *sd, *prefer = NULL; struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask); int this_cpu = smp_processor_id(); int cpu = task_cpu(task); + int fallback_cpu = -1; /* Make sure the mask is initialized first */ if (unlikely(!lowest_mask)) @@ -1668,9 +1691,29 @@ static int find_lowest_rq(struct task_struct *task) return this_cpu; } - best_cpu = cpumask_first_and(lowest_mask, - sched_domain_span(sd)); + best_cpu = find_cpu(lowest_mask, sd, prefer); + if (best_cpu < nr_cpu_ids) { + /* + * If current domain is SD_PREFER_SIBLING + * flaged, we have to try to check other + * siblings first. + */ + if (sd->flags & SD_PREFER_SIBLING) { + prefer = sd; + + /* + * fallback_cpu should be one + * in the closest domain among + * SD_PREFER_SIBLING domains, + * in case that more than one + * SD_PREFER_SIBLING domains + * exist in the hierachy. + */ + if (fallback_cpu == -1) + fallback_cpu = best_cpu; + continue; + } rcu_read_unlock(); return best_cpu; } @@ -1679,6 +1722,13 @@ static int find_lowest_rq(struct task_struct *task) rcu_read_unlock(); /* + * If fallback_cpu is valid, all our guesses failed *except* for + * SD_PREFER_SIBLING domain. Now, we can return the fallback cpu. + */ + if (fallback_cpu != -1) + return fallback_cpu; + + /* * And finally, if there were no matches within the domains * just give the caller *something* to work with from the compatible * locations. -- 1.9.1