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. This patch adds a new cpudl_set_freecpu() to initialize cpudl.free_cpus when rq_attach_root(), and modifies cpudl_find() and all its call sites in order to address these problems. Signed-off-by: pang.xunlei <[email protected]> --- kernel/sched/core.c | 2 ++ kernel/sched/cpudeadline.c | 41 ++++++++++++++++++++++------------------- kernel/sched/cpudeadline.h | 1 + kernel/sched/deadline.c | 32 +++++++++++++++----------------- 4 files changed, 40 insertions(+), 36 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 240157c..17d5778 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5584,6 +5584,8 @@ static void rq_attach_root(struct rq *rq, struct root_domain *rd) rq->rd = rd; cpumask_set_cpu(rq->cpu, rd->span); + cpudl_set_freecpu(rq->cpu, &rd->cpudl); + if (cpumask_test_cpu(rq->cpu, cpu_active_mask)) set_rq_online(rq); diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c index 539ca3c..1dd446a 100644 --- a/kernel/sched/cpudeadline.c +++ b/kernel/sched/cpudeadline.c @@ -97,30 +97,25 @@ 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 to fill in with the selected CPUs (not NULL) * - * 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) { - int best_cpu = -1; 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) && - 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); + cpumask_and(later_mask, cpu_active_mask, &p->cpus_allowed); + if (cpumask_and(later_mask, later_mask, cp->free_cpus)) { + return 1; + } else if (cpumask_and(later_mask, cpumask_of(cpudl_maximum(cp)), + &p->cpus_allowed) && + dl_time_before(dl_se->deadline, cp->elements[0].dl)) { + return 1; } -out: - WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); - - return best_cpu; + return 0; } /* @@ -165,7 +160,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid) old_idx = parent(old_idx); } cpumask_set_cpu(cpu, cp->free_cpus); - cpudl_heapify(cp, old_idx); + cpudl_heapify(cp, old_idx); goto out; } @@ -186,6 +181,16 @@ out: } /* + * cpudl_set_freecpu - Set the cpudl.free_cpus + * @cpu: rd attached cpu + * @cp: the cpudl max-heap context + */ +void cpudl_set_freecpu(int cpu, struct cpudl *cp) +{ + cpumask_set_cpu(cpu, cp->free_cpus); +} + +/* * cpudl_init - initialize the cpudl structure * @cp: the cpudl max-heap context */ @@ -203,7 +208,7 @@ int cpudl_init(struct cpudl *cp) if (!cp->elements) return -ENOMEM; - if (!alloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) { + if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) { kfree(cp->elements); return -ENOMEM; } @@ -211,8 +216,6 @@ int cpudl_init(struct cpudl *cp) for_each_possible_cpu(i) cp->elements[i].idx = IDX_INVALID; - cpumask_setall(cp->free_cpus); - return 0; } diff --git a/kernel/sched/cpudeadline.h b/kernel/sched/cpudeadline.h index 020039b..71478fc 100644 --- a/kernel/sched/cpudeadline.h +++ b/kernel/sched/cpudeadline.h @@ -25,6 +25,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, 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); +void cpudl_set_freecpu(int cpu, struct cpudl *cp); #endif /* CONFIG_SMP */ #endif /* _LINUX_CPUDL_H */ diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 5285332..e0e8013 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -965,14 +965,18 @@ 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) + !cpudl_find(&rq->rd->cpudl, rq->curr, later_mask)) return; /* @@ -980,7 +984,7 @@ 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, NULL) != -1) + cpudl_find(&rq->rd->cpudl, p, later_mask)) return; resched_curr(rq); @@ -1167,14 +1171,12 @@ 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)) @@ -1187,14 +1189,12 @@ 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, 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)) 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. @@ -1219,6 +1219,7 @@ 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) { /* @@ -1231,12 +1232,9 @@ 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; } -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
