diff options
| -rw-r--r-- | include/linux/sched/topology.h | 8 | ||||
| -rw-r--r-- | kernel/sched/fair.c | 126 | ||||
| -rw-r--r-- | kernel/sched/features.h | 1 |
3 files changed, 16 insertions, 119 deletions
diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h index d7b6dab..7d065ab 100644 --- a/include/linux/sched/topology.h +++ b/include/linux/sched/topology.h @@ -71,14 +71,6 @@ struct sched_domain_shared { atomic_t ref; atomic_t nr_busy_cpus; int has_idle_cores; - - /* - * Some variables from the most recent sd_lb_stats for this domain, - * used by wake_affine(). - */ - unsigned long nr_running; - unsigned long load; - unsigned long capacity; }; struct sched_domain { diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 70ba32e..28cabed 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5356,115 +5356,36 @@ static int wake_wide(struct task_struct *p) return 1; } -struct llc_stats { - unsigned long nr_running; - unsigned long load; - unsigned long capacity; - int has_capacity; -}; - -static bool get_llc_stats(struct llc_stats *stats, int cpu) -{ - struct sched_domain_shared *sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); - - if (!sds) - return false; - - stats->nr_running = READ_ONCE(sds->nr_running); - stats->load = READ_ONCE(sds->load); - stats->capacity = READ_ONCE(sds->capacity); - stats->has_capacity = stats->nr_running < per_cpu(sd_llc_size, cpu); - - return true; -} - /* - * Can a task be moved from prev_cpu to this_cpu without causing a load - * imbalance that would trigger the load balancer? + * The purpose of wake_affine() is to quickly determine on which CPU we can run + * soonest. For the purpose of speed we only consider the waking and previous + * CPU. * - * Since we're running on 'stale' values, we might in fact create an imbalance - * but recomputing these values is expensive, as that'd mean iteration 2 cache - * domains worth of CPUs. + * wake_affine_idle() - only considers 'now', it check if the waking CPU is (or + * will be) idle. */ + static bool -wake_affine_llc(struct sched_domain *sd, struct task_struct *p, - int this_cpu, int prev_cpu, int sync) +wake_affine_idle(struct sched_domain *sd, struct task_struct *p, + int this_cpu, int prev_cpu, int sync) { - struct llc_stats prev_stats, this_stats; - s64 this_eff_load, prev_eff_load; - unsigned long task_load; - - if (!get_llc_stats(&prev_stats, prev_cpu) || - !get_llc_stats(&this_stats, this_cpu)) - return false; - - /* - * If sync wakeup then subtract the (maximum possible) - * effect of the currently running task from the load - * of the current LLC. - */ - if (sync) { - unsigned long current_load = task_h_load(current); - - /* in this case load hits 0 and this LLC is considered 'idle' */ - if (current_load > this_stats.load) - return true; - - this_stats.load -= current_load; - } - - /* - * The has_capacity stuff is not SMT aware, but by trying to balance - * the nr_running on both ends we try and fill the domain at equal - * rates, thereby first consuming cores before siblings. - */ - - /* if the old cache has capacity, stay there */ - if (prev_stats.has_capacity && prev_stats.nr_running < this_stats.nr_running+1) - return false; - - /* if this cache has capacity, come here */ - if (this_stats.has_capacity && this_stats.nr_running+1 < prev_stats.nr_running) + if (idle_cpu(this_cpu)) return true; - /* - * Check to see if we can move the load without causing too much - * imbalance. - */ - task_load = task_h_load(p); - - this_eff_load = 100; - this_eff_load *= prev_stats.capacity; - - prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2; - prev_eff_load *= this_stats.capacity; - - this_eff_load *= this_stats.load + task_load; - prev_eff_load *= prev_stats.load - task_load; + if (sync && cpu_rq(this_cpu)->nr_running == 1) + return true; - return this_eff_load <= prev_eff_load; + return false; } static int wake_affine(struct sched_domain *sd, struct task_struct *p, int prev_cpu, int sync) { int this_cpu = smp_processor_id(); - bool affine; - - /* - * Default to no affine wakeups; wake_affine() should not effect a task - * placement the load-balancer feels inclined to undo. The conservative - * option is therefore to not move tasks when they wake up. - */ - affine = false; + bool affine = false; - /* - * If the wakeup is across cache domains, try to evaluate if movement - * makes sense, otherwise rely on select_idle_siblings() to do - * placement inside the cache domain. - */ - if (!cpus_share_cache(prev_cpu, this_cpu)) - affine = wake_affine_llc(sd, p, this_cpu, prev_cpu, sync); + if (sched_feat(WA_IDLE) && !affine) + affine = wake_affine_idle(sd, p, this_cpu, prev_cpu, sync); schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts); if (affine) { @@ -7600,7 +7521,6 @@ static inline enum fbq_type fbq_classify_rq(struct rq *rq) */ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds) { - struct sched_domain_shared *shared = env->sd->shared; struct sched_domain *child = env->sd->child; struct sched_group *sg = env->sd->groups; struct sg_lb_stats *local = &sds->local_stat; @@ -7672,22 +7592,6 @@ next_group: if (env->dst_rq->rd->overload != overload) env->dst_rq->rd->overload = overload; } - - if (!shared) - return; - - /* - * Since these are sums over groups they can contain some CPUs - * multiple times for the NUMA domains. - * - * Currently only wake_affine_llc() and find_busiest_group() - * uses these numbers, only the last is affected by this problem. - * - * XXX fix that. - */ - WRITE_ONCE(shared->nr_running, sds->total_running); - WRITE_ONCE(shared->load, sds->total_load); - WRITE_ONCE(shared->capacity, sds->total_capacity); } /** diff --git a/kernel/sched/features.h b/kernel/sched/features.h index d3fb155..0a519f8 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -81,3 +81,4 @@ SCHED_FEAT(RT_RUNTIME_SHARE, true) SCHED_FEAT(LB_MIN, false) SCHED_FEAT(ATTACH_AGE_LOAD, true) +SCHED_FEAT(WA_IDLE, true) |
