From: Thara Gopinath Date: Fri, 23 Jun 2017 14:37:05 +0000 (-0400) Subject: Per Sched domain over utilization X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=d5cd121ea0d58479ed4dff36a41bce1ea9bb59ad;p=platform%2Fkernel%2Flinux-exynos.git Per Sched domain over utilization The current implementation of overutilization, aborts energy aware scheduling if any cpu in the system is over-utilized. This patch introduces over utilization flag per sched domain level instead of a single flag system wide. Load balancing is done at the sched domain where any of the cpu is over utilized. If energy aware scheduling is enabled and no cpu in a sched domain is overuttilized, load balancing is skipped for that sched domain and energy aware scheduling continues at that level. The implementation takes advantage of the shared sched_domain structure that is common across all the sched domains at a level. The new flag introduced is placed in this structure so that all the sched domains the same level share the flag. In case of an overutilized cpu, the flag gets set at level1 sched_domain. The flag at the parent sched_domain level gets set in either of the two following scenarios. 1. There is a misfit task in one of the cpu's in this sched_domain. 2. The total utilization of the domain is greater than the domain capacity The flag is cleared if no cpu in a sched domain is overutilized. This implementation still can have corner scenarios with respect to misfit tasks. For example consider a sched group with n cpus and n+1 70%utilized tasks. Ideally this is a case for load balance to happen in a parent sched domain. But neither the total group utilization is high enough for the load balance to be triggered in the parent domain nor there is a cpu with a single overutilized task so that aload balance is triggered in a parent domain. But again this could be a purely academic sceanrio, as during task wake up these tasks will be placed more appropriately. Signed-off-by: Thara Gopinath Signed-off-by: Lukasz Luba --- diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h index 4b5f3c3cbb36..e0161c3da0da 100644 --- a/include/linux/sched/topology.h +++ b/include/linux/sched/topology.h @@ -89,6 +89,8 @@ struct sched_domain_shared { atomic_t ref; atomic_t nr_busy_cpus; int has_idle_cores; + + bool overutilized; }; struct sched_domain { diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fdfb2e51c815..d56d33dd94b5 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5155,6 +5155,21 @@ static inline void hrtick_update(struct rq *rq) static bool cpu_overutilized(int cpu); +static bool sd_overutilized(struct sched_domain *sd) +{ + return sd->shared->overutilized; +} + +static void set_sd_overutilized(struct sched_domain *sd) +{ + sd->shared->overutilized = true; +} + +static void clear_sd_overutilized(struct sched_domain *sd) +{ + sd->shared->overutilized = false; +} + /* * The enqueue_task method is called before nr_running is * increased. Here we update the fair scheduling stats and @@ -5164,6 +5179,7 @@ static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) { struct cfs_rq *cfs_rq; + struct sched_domain *sd; struct sched_entity *se = &p->se; int task_new = !(flags & ENQUEUE_WAKEUP); @@ -5207,9 +5223,12 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) if (!se) { add_nr_running(rq, 1); - if (!task_new && !rq->rd->overutilized && + rcu_read_lock(); + sd = rcu_dereference(rq->sd); + if (!task_new && sd && !sd_overutilized(sd) && cpu_overutilized(rq->cpu)) - rq->rd->overutilized = true; + set_sd_overutilized(sd); + rcu_read_unlock(); } hrtick_update(rq); } @@ -6564,8 +6583,6 @@ static int select_energy_cpu_brute(struct task_struct *p, int prev_cpu) unsigned long max_spare = 0; struct sched_domain *sd; - rcu_read_lock(); - sd = rcu_dereference(per_cpu(sd_ea, prev_cpu)); if (!sd) @@ -6603,8 +6620,6 @@ static int select_energy_cpu_brute(struct task_struct *p, int prev_cpu) } unlock: - rcu_read_unlock(); - if (energy_cpu == prev_cpu && !cpu_overutilized(prev_cpu)) return prev_cpu; @@ -6638,10 +6653,15 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f && cpumask_test_cpu(cpu, &p->cpus_allowed); } - if (energy_aware() && !(cpu_rq(prev_cpu)->rd->overutilized)) - return select_energy_cpu_brute(p, prev_cpu); - rcu_read_lock(); + sd = rcu_dereference(cpu_rq(prev_cpu)->sd); + if (energy_aware() && sd && !sd_overutilized(sd)) { + new_cpu = select_energy_cpu_brute(p, prev_cpu); + goto unlock; + } + + sd = NULL; + for_each_domain(cpu, tmp) { if (!(tmp->flags & SD_LOAD_BALANCE)) break; @@ -6688,6 +6708,8 @@ pick_cpu: } else { new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag); } + +unlock: rcu_read_unlock(); #ifdef CONFIG_NO_HZ_COMMON @@ -7816,6 +7838,7 @@ struct sd_lb_stats { unsigned long total_running; unsigned long total_load; /* Total load of all groups in sd */ unsigned long total_capacity; /* Total capacity of all groups in sd */ + unsigned long total_util; /* Total util of all groups in sd */ unsigned long avg_load; /* Average load across all groups in sd */ struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */ @@ -7836,6 +7859,7 @@ static inline void init_sd_lb_stats(struct sd_lb_stats *sds) .total_running = 0UL, .total_load = 0UL, .total_capacity = 0UL, + .total_util = 0UL, .busiest_stat = { .avg_load = 0UL, .sum_nr_running = 0, @@ -8131,7 +8155,7 @@ group_type group_classify(struct sched_group *group, static inline void update_sg_lb_stats(struct lb_env *env, struct sched_group *group, int load_idx, int local_group, struct sg_lb_stats *sgs, - bool *overload, bool *overutilized) + bool *overload, bool *overutilized, bool *misfit_task) { unsigned long load; int i, nr_running; @@ -8170,8 +8194,12 @@ static inline void update_sg_lb_stats(struct lb_env *env, !sgs->group_misfit_task && rq->misfit_task) sgs->group_misfit_task = capacity_of(i); - if (cpu_overutilized(i)) + if (cpu_overutilized(i)) { *overutilized = true; + + if (rq->misfit_task) + *misfit_task = true; + } } /* Adjust by relative CPU capacity of the group */ @@ -8328,7 +8356,7 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd struct sg_lb_stats *local = &sds->local_stat; struct sg_lb_stats tmp_sgs; int load_idx, prefer_sibling = 0; - bool overload = false, overutilized = false; + bool overload = false, overutilized = false, misfit_task = false; if (child && child->flags & SD_PREFER_SIBLING) prefer_sibling = 1; @@ -8373,7 +8401,8 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd } update_sg_lb_stats(env, sg, load_idx, local_group, sgs, - &overload, &overutilized); + &overload, &overutilized, + &misfit_task); if (local_group) goto next_group; @@ -8405,6 +8434,7 @@ next_group: sds->total_running += sgs->sum_nr_running; sds->total_load += sgs->group_load; sds->total_capacity += sgs->group_capacity; + sds->total_util += sgs->group_util; sg = sg->next; } while (sg != env->sd->groups); @@ -8418,14 +8448,46 @@ next_group: /* update overload indicator if we are at root domain */ if (env->dst_rq->rd->overload != overload) env->dst_rq->rd->overload = overload; + } - /* Update over-utilization (tipping point, U >= 0) indicator */ - if (env->dst_rq->rd->overutilized != overutilized) - env->dst_rq->rd->overutilized = overutilized; - } else { - if (!env->dst_rq->rd->overutilized && overutilized) - env->dst_rq->rd->overutilized = true; + if (overutilized) + set_sd_overutilized(env->sd); + else + clear_sd_overutilized(env->sd); + + /* + * If there is a misfit task in one cpu in this sched_domain + * it is likely that the imbalance cannot be sorted out among + * the cpu's in this sched_domain. In this case set the + * overutilized flag at the parent sched_domain. + */ + if (misfit_task) { + struct sched_domain *sd = env->sd->parent; + + /* + * In case of a misfit task, load balance at the parent + * sched domain level will make sense only if the the cpus + * have a different capacity. If cpus at a domain level have + * the same capacity, the misfit task cannot be well + * accomodated in any of the cpus and there in no point in + * trying a load balance at this level + */ + while (sd) { + if (sd->flags & SD_ASYM_CPUCAPACITY) { + set_sd_overutilized(sd); + break; + } + sd = sd->parent; + } } + + /* + * If the domain util is greater that domain capacity, load balancing + * needs to be done at the next sched domain level as well. + */ + if (lb_sd_parent(env->sd) && + sds->total_capacity * 1024 < sds->total_util * capacity_margin) + set_sd_overutilized(env->sd->parent); } /** @@ -8652,7 +8714,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env) */ update_sd_lb_stats(env, &sds); - if (energy_aware() && !env->dst_rq->rd->overutilized) + if (energy_aware() && !sd_overutilized(env->sd)) goto out_balanced; local = &sds.local_stat; @@ -9581,6 +9643,9 @@ static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle) } max_cost += sd->max_newidle_lb_cost; + if (energy_aware() && !sd_overutilized(sd)) + continue; + if (!(sd->flags & SD_LOAD_BALANCE)) continue; @@ -9910,6 +9975,7 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) { struct cfs_rq *cfs_rq; struct sched_entity *se = &curr->se; + struct sched_domain *sd; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); @@ -9921,8 +9987,11 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) rq->misfit_task = !task_fits_capacity(curr, capacity_of(rq->cpu)); - if (!rq->rd->overutilized && cpu_overutilized(task_cpu(curr))) - rq->rd->overutilized = true; + rcu_read_lock(); + sd = rcu_dereference(rq->sd); + if (sd && !sd_overutilized(sd) && cpu_overutilized(task_cpu(curr))) + set_sd_overutilized(sd); + rcu_read_unlock(); } /* diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 549cbda7bff9..0dab02acac26 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -627,9 +627,6 @@ struct root_domain { /* Indicate more than one runnable task for any CPU */ bool overload; - /* Indicate one or more cpus over-utilized (tipping point) */ - bool overutilized; - /* * The bit corresponding to a CPU gets set here if such CPU has more * than one runnable -deadline task (as it is below for RT tasks). diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index ce82adec1daf..d19d513c0403 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -1279,15 +1279,11 @@ sd_init(struct sched_domain_topology_level *tl, sd->idle_idx = 1; } - /* - * For all levels sharing cache; connect a sched_domain_shared - * instance. - */ - if (sd->flags & SD_SHARE_PKG_RESOURCES) { - sd->shared = *per_cpu_ptr(sdd->sds, sd_id); - atomic_inc(&sd->shared->ref); + sd->shared = *per_cpu_ptr(sdd->sds, sd_id); + atomic_inc(&sd->shared->ref); + + if (sd->flags & SD_SHARE_PKG_RESOURCES) atomic_set(&sd->shared->nr_busy_cpus, sd_weight); - } sd->private = sdd;