Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757825AbaKTR3G (ORCPT ); Thu, 20 Nov 2014 12:29:06 -0500 Received: from mail-pa0-f50.google.com ([209.85.220.50]:56223 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751911AbaKTR3C (ORCPT ); Thu, 20 Nov 2014 12:29:02 -0500 From: "pang.xunlei" To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Steven Rostedt , Juri Lelli , "pang.xunlei" Subject: [PATCH v3 3/3] sched/deadline: Change the return meaning of cpudl_find() Date: Fri, 21 Nov 2014 01:28:05 +0800 Message-Id: <1416504485-8180-3-git-send-email-pang.xunlei@linaro.org> X-Mailer: git-send-email 2.0.4 In-Reply-To: <1416504485-8180-1-git-send-email-pang.xunlei@linaro.org> References: <1416504485-8180-1-git-send-email-pang.xunlei@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org cpudl_find() is not a good place to select the best cpu, so leave this role to its call site, currently it is find_later_rq() where we can do the election of the best cpu according to sd topology. This patch tackles cpudl_find() using a trick with its return value: - define macros for the return values of cpudl_find(): then, with return value >=0, means it returns the only available cpu. - In the leg of "if", it can just return CPUDL_FIND_CPUMASK, as we want to select the best_cpu in find_later_rq(). In the leg of "else if", just returns cpudl_maximum(cp), apparently there is no need to set the later_mask, since we will definitely select this cpu as the best_cpu in find_later_rq() . - Convert all its call sites to reflect this return meaning change. Sync find_later_rq()'s processing logic of best cpu election to that of RT find_lowest_rq(). Additionally, this patch avoids the extra cpumask_set_cpu() operation in cpudl_find() as well. Signed-off-by: pang.xunlei --- kernel/sched/cpudeadline.c | 16 +++++++--------- kernel/sched/cpudeadline.h | 3 +++ kernel/sched/deadline.c | 17 ++++++++--------- 3 files changed, 18 insertions(+), 18 deletions(-) diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c index c01b3aa..f17e6af 100644 --- a/kernel/sched/cpudeadline.c +++ b/kernel/sched/cpudeadline.c @@ -99,28 +99,26 @@ static inline int cpudl_maximum(struct cpudl *cp) * @p: the task * @later_mask: a mask to fill in with the selected CPUs (not NULL) * - * Returns: int - best CPU (heap maximum if suitable) + * Returns: int + * CPUDL_FIND_NONE: no available cpus; + * CPUDL_FIND_CPUMASK: available cpus in later_mask + * >=0: the only one available 0-based cpu */ int cpudl_find(struct cpudl *cp, struct task_struct *p, struct cpumask *later_mask) { - int best_cpu = -1; const struct sched_dl_entity *dl_se = &p->dl; cpumask_and(later_mask, cpu_active_mask, &p->cpus_allowed); if (cpumask_and(later_mask, later_mask, cp->free_cpus)) { - best_cpu = cpumask_any(later_mask); - goto out; + return CPUDL_FIND_CPUMASK; } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) && dl_time_before(dl_se->deadline, cp->elements[0].dl)) { - best_cpu = cpudl_maximum(cp); - cpumask_set_cpu(best_cpu, later_mask); + return cpudl_maximum(cp); } -out: - WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); - return best_cpu; + return CPUDL_FIND_NONE; } /* diff --git a/kernel/sched/cpudeadline.h b/kernel/sched/cpudeadline.h index 4a10a65..235f2b9 100755 --- a/kernel/sched/cpudeadline.h +++ b/kernel/sched/cpudeadline.h @@ -3,6 +3,9 @@ #include +#define CPUDL_FIND_NONE -2 /* no available cpus */ +#define CPUDL_FIND_CPUMASK -1 /* available cpus in later_mask */ + #define IDX_INVALID -1 struct cpudl_item { diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 03bb3f0..bb37506 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -980,7 +980,7 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p) * let's hope p can move out. */ if (rq->curr->nr_cpus_allowed == 1 || - cpudl_find(&rq->rd->cpudl, rq->curr, later_mask) == -1) + cpudl_find(&rq->rd->cpudl, rq->curr, later_mask) == CPUDL_FIND_NONE) return; /* @@ -988,7 +988,7 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p) * see if it is pushed or pulled somewhere else. */ if (p->nr_cpus_allowed != 1 && - cpudl_find(&rq->rd->cpudl, p, later_mask) != -1) + cpudl_find(&rq->rd->cpudl, p, later_mask) != CPUDL_FIND_NONE) return; resched_curr(rq); @@ -1195,8 +1195,10 @@ static int find_later_rq(struct task_struct *task) */ best_cpu = cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask); - if (best_cpu == -1) + if (best_cpu == CPUDL_FIND_NONE) return -1; + if (best_cpu != CPUDL_FIND_CPUMASK) + return best_cpu; /* * If we are here, some target has been found, @@ -1234,12 +1236,9 @@ static int find_later_rq(struct task_struct *task) return this_cpu; } - /* - * Last chance: if best_cpu is valid and is - * in the mask, that becomes our choice. - */ - if (best_cpu < nr_cpu_ids && - cpumask_test_cpu(best_cpu, sched_domain_span(sd))) { + best_cpu = cpumask_first_and(later_mask, + sched_domain_span(sd)); + if (best_cpu < nr_cpu_ids) { rcu_read_unlock(); return best_cpu; } -- 2.1.0 -- 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/