From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751906AbbASEwh (ORCPT ); Sun, 18 Jan 2015 23:52:37 -0500 Received: from mail-qa0-f46.google.com ([209.85.216.46]:51894 "EHLO mail-qa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751128AbbASEv6 (ORCPT ); Sun, 18 Jan 2015 23:51:58 -0500 From: Xunlei Pang To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Juri Lelli , Xunlei Pang Subject: [PATCH 5/5] sched/rt: Optimize find_lowest_rq() to select a cache hot cpu Date: Mon, 19 Jan 2015 04:49:40 +0000 Message-Id: <1421642980-10045-5-git-send-email-pang.xunlei@linaro.org> X-Mailer: git-send-email 2.2.1 In-Reply-To: <1421642980-10045-1-git-send-email-pang.xunlei@linaro.org> References: <1421642980-10045-1-git-send-email-pang.xunlei@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In find_lowest_rq(), if we can't find a wake_affine cpu from sched_domain, then we can actually determine a cache hot cpu instead of simply calling "cpumask_any(lowest_mask)" which always returns the first cpu in the mask. So, we can determine the cache hot cpu during the interation of sched_domain() in passing. Signed-off-by: Xunlei Pang --- kernel/sched/rt.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index d28cfa4..e6a42e6 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1535,6 +1535,7 @@ static int find_lowest_rq(struct task_struct *task) struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask); int this_cpu = smp_processor_id(); int cpu = task_cpu(task); + int cachehot_cpu = nr_cpu_ids; /* Make sure the mask is initialized first */ if (unlikely(!lowest_mask)) @@ -1566,8 +1567,12 @@ static int find_lowest_rq(struct task_struct *task) rcu_read_lock(); for_each_domain(cpu, sd) { + if (cachehot_cpu >= nr_cpu_ids) + cachehot_cpu = cpumask_first_and(lowest_mask, + sched_domain_span(sd)); + if (sd->flags & SD_WAKE_AFFINE) { - int best_cpu; + int wakeaffine_cpu; /* * "this_cpu" is cheaper to preempt than a @@ -1579,16 +1584,20 @@ static int find_lowest_rq(struct task_struct *task) return this_cpu; } - best_cpu = cpumask_first_and(lowest_mask, + wakeaffine_cpu = cpumask_first_and(lowest_mask, sched_domain_span(sd)); - if (best_cpu < nr_cpu_ids) { + if (wakeaffine_cpu < nr_cpu_ids) { rcu_read_unlock(); - return best_cpu; + return wakeaffine_cpu; } } } rcu_read_unlock(); + /* most likely cache-hot */ + if (cachehot_cpu < nr_cpu_ids) + return cachehot_cpu; + /* * And finally, if there were no matches within the domains * just give the caller *something* to work with from the compatible -- 1.9.1