Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755500AbaKEPtF (ORCPT ); Wed, 5 Nov 2014 10:49:05 -0500 Received: from mail-pd0-f174.google.com ([209.85.192.174]:42231 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755183AbaKEPtC (ORCPT ); Wed, 5 Nov 2014 10:49:02 -0500 From: "pang.xunlei" To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Steven Rostedt , Juri Lelli , "pang.xunlei" Subject: [PATCH v3 4/7] sched/deadline: Fix several problems with cpudl_find() Date: Wed, 5 Nov 2014 23:48:23 +0800 Message-Id: <1415202506-7800-4-git-send-email-pang.xunlei@linaro.org> X-Mailer: git-send-email 2.0.4 In-Reply-To: <1415202506-7800-1-git-send-email-pang.xunlei@linaro.org> References: <1415202506-7800-1-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() has some problems: 1)in check_preempt_equal_dl(), called with NULL later_mask, thus cpudl_find() doesn't check cpudl.free_cpus at all. 2)Also, the whole system isn't always overloaded with many DL tasks in which cases all the cpu may have a DL task running, so it may return the best cpu, because we only return the first maximum deadline cpu(is there a need to iterate the same deadline value to find more different cpus if possible?). So it may be reasonable to change the return value of cpudl_find() to a bool type, because it isn't always the best cpu actually which can be better determined in find_later_rq() via sched_domain topology. 3)in the "else if" branch, uses cpus_allowed to test again. This patch syncs the logic in a former patch by "Juri Lelli", then problem 1) will be solved naturally, and modifies cpudl_find() and all its call sites to address these problems. The former patch by "Juri Lelli" is: "sched/deadline: Fix inter- exclusive cpusets migrations" Signed-off-by: pang.xunlei --- kernel/sched/cpudeadline.c | 29 ++++++++++++++--------------- kernel/sched/cpudeadline.h | 2 +- kernel/sched/deadline.c | 45 ++++++++++++++++++++++++++------------------- 3 files changed, 41 insertions(+), 35 deletions(-) diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c index 539ca3c..72a3da3 100644 --- a/kernel/sched/cpudeadline.c +++ b/kernel/sched/cpudeadline.c @@ -97,30 +97,29 @@ static inline int cpudl_maximum(struct cpudl *cp) * cpudl_find - find the best (later-dl) CPU in the system * @cp: the cpudl max-heap context * @p: the task - * @later_mask: a mask to fill in with the selected CPUs (or NULL) + * @later_mask: a mask used to filter cpus, also used to fill + * in with the selected CPUs if set_flag is set. Not NULL. + * @set_flag: a flag to determine if should set the later_mask. * - * Returns: int - best CPU (heap maximum if suitable) + * Returns: (int)bool - CPUs were found */ int cpudl_find(struct cpudl *cp, struct task_struct *p, - struct cpumask *later_mask) + struct cpumask *later_mask, int set_flag) { - int best_cpu = -1; + struct cpumask tmp_mask; const struct sched_dl_entity *dl_se = &p->dl; - if (later_mask && cpumask_and(later_mask, later_mask, cp->free_cpus)) { - best_cpu = cpumask_any(later_mask); - goto out; - } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) && + + if (cpumask_and(&tmp_mask, later_mask, cp->free_cpus)) { + if (set_flag) + cpumask_copy(later_mask, &tmp_mask); + return 1; + } else if (cpumask_and(later_mask, later_mask, cpumask_of(cpudl_maximum(cp))) && dl_time_before(dl_se->deadline, cp->elements[0].dl)) { - best_cpu = cpudl_maximum(cp); - if (later_mask) - cpumask_set_cpu(best_cpu, later_mask); + return 1; } -out: - WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); - - return best_cpu; + return 0; } /* diff --git a/kernel/sched/cpudeadline.h b/kernel/sched/cpudeadline.h index 538c979..0c9636e 100644 --- a/kernel/sched/cpudeadline.h +++ b/kernel/sched/cpudeadline.h @@ -21,7 +21,7 @@ struct cpudl { #ifdef CONFIG_SMP int cpudl_find(struct cpudl *cp, struct task_struct *p, - struct cpumask *later_mask); + struct cpumask *later_mask, int set_flag); void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid); int cpudl_init(struct cpudl *cp); void cpudl_cleanup(struct cpudl *cp); diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 256e577..42edfcd 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -946,23 +946,34 @@ out: return cpu; } +static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl); + static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p) { + struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl); + /* * Current can't be migrated, useless to reschedule, * let's hope p can move out. */ - if (rq->curr->nr_cpus_allowed == 1 || - cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1) + if (rq->curr->nr_cpus_allowed == 1) + return; + + cpumask_and(later_mask, rq->rd->span, cpu_active_mask); + cpumask_and(later_mask, later_mask, &rq->curr->cpus_allowed); + if (!cpudl_find(&rq->rd->cpudl, rq->curr, later_mask, 0)) return; /* * p is migratable, so let's not schedule it and * see if it is pushed or pulled somewhere else. */ - if (p->nr_cpus_allowed != 1 && - cpudl_find(&rq->rd->cpudl, p, NULL) != -1) - return; + if (p->nr_cpus_allowed != 1) { + cpumask_and(later_mask, rq->rd->span, cpu_active_mask); + cpumask_and(later_mask, later_mask, &p->cpus_allowed); + if (cpudl_find(&rq->rd->cpudl, p, later_mask, 0)) + return; + } resched_curr(rq); } @@ -1148,14 +1159,12 @@ next_node: return NULL; } -static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl); - 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)) @@ -1168,14 +1177,14 @@ 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. */ - cpumask_copy(later_mask, task_rq(task)->rd->span); - cpumask_and(later_mask, later_mask, cpu_active_mask); + cpumask_and(later_mask, task_rq(task)->rd->span, cpu_active_mask); cpumask_and(later_mask, later_mask, &task->cpus_allowed); - 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 (cpumask_weight(later_mask) == 1) + return cpumask_any(later_mask); + /* * If we are here, some target has been found, * the most suitable of which is cached in best_cpu. @@ -1200,6 +1209,7 @@ static int find_later_rq(struct task_struct *task) rcu_read_lock(); for_each_domain(cpu, sd) { + int best_cpu; if (sd->flags & SD_WAKE_AFFINE) { /* @@ -1212,12 +1222,9 @@ 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/