sched: improve affine wakeups

[mirror_ubuntu-zesty-kernel.git] / kernel / sched_fair.c

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index b5a357396b491d6326d507e1d814ebf535f05efe..87c9d3a2aafa405757e4776f4319e7ca7a346f31 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -556,6 +556,21 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
        account_entity_enqueue(cfs_rq, se);
 }
 
+static void update_avg(u64 *avg, u64 sample)
+{
+       s64 diff = sample - *avg;
+       *avg += diff >> 3;
+}
+
+static void update_avg_stats(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+       if (!se->last_wakeup)
+               return;
+
+       update_avg(&se->avg_overlap, se->sum_exec_runtime - se->last_wakeup);
+       se->last_wakeup = 0;
+}
+
 static void
 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
 {
@@ -566,6 +581,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
 
        update_stats_dequeue(cfs_rq, se);
        if (sleep) {
+               update_avg_stats(cfs_rq, se);
 #ifdef CONFIG_SCHEDSTATS
                if (entity_is_task(se)) {
                        struct task_struct *tsk = task_of(se);
@@ -981,12 +997,15 @@ static inline int wake_idle(int cpu, struct task_struct *p)
 
 #ifdef CONFIG_SMP
 
+static const struct sched_class fair_sched_class;
+
 static int
-wake_affine(struct rq *rq, struct sched_domain *this_sd, struct task_struct *p,
-           int prev_cpu, int this_cpu, int sync, int idx,
-           unsigned long load, unsigned long this_load,
+wake_affine(struct rq *rq, struct sched_domain *this_sd, struct rq *this_rq,
+           struct task_struct *p, int prev_cpu, int this_cpu, int sync,
+           int idx, unsigned long load, unsigned long this_load,
            unsigned int imbalance)
 {
+       struct task_struct *curr = this_rq->curr;
        unsigned long tl = this_load;
        unsigned long tl_per_task;
 
@@ -994,10 +1013,15 @@ wake_affine(struct rq *rq, struct sched_domain *this_sd, struct task_struct *p,
                return 0;
 
        /*
-        * Attract cache-cold tasks on sync wakeups:
+        * If the currently running task will sleep within
+        * a reasonable amount of time then attract this newly
+        * woken task:
         */
-       if (sync && !task_hot(p, rq->clock, this_sd))
-               return 1;
+       if (sync && curr->sched_class == &fair_sched_class) {
+               if (curr->se.avg_overlap < sysctl_sched_migration_cost &&
+                               p->se.avg_overlap < sysctl_sched_migration_cost)
+                       return 1;
+       }
 
        schedstat_inc(p, se.nr_wakeups_affine_attempts);
        tl_per_task = cpu_avg_load_per_task(this_cpu);
@@ -1030,18 +1054,16 @@ static int select_task_rq_fair(struct task_struct *p, int sync)
        struct sched_domain *sd, *this_sd = NULL;
        int prev_cpu, this_cpu, new_cpu;
        unsigned long load, this_load;
+       struct rq *rq, *this_rq;
        unsigned int imbalance;
-       struct rq *rq;
        int idx;
 
        prev_cpu        = task_cpu(p);
        rq              = task_rq(p);
        this_cpu        = smp_processor_id();
+       this_rq         = cpu_rq(this_cpu);
        new_cpu         = prev_cpu;
 
-       if (prev_cpu == this_cpu)
-               goto out;
-
        /*
         * 'this_sd' is the first domain that both
         * this_cpu and prev_cpu are present in:
@@ -1069,11 +1091,12 @@ static int select_task_rq_fair(struct task_struct *p, int sync)
        load = source_load(prev_cpu, idx);
        this_load = target_load(this_cpu, idx);
 
-       if (wake_affine(rq, this_sd, p, prev_cpu, this_cpu, sync, idx,
-                                    load, this_load, imbalance)) {
-               new_cpu = this_cpu;
+       if (wake_affine(rq, this_sd, this_rq, p, prev_cpu, this_cpu, sync, idx,
+                                    load, this_load, imbalance))
+               return this_cpu;
+
+       if (prev_cpu == this_cpu)
                goto out;
-       }
 
        /*
         * Start passive balancing when half the imbalance_pct
@@ -1083,8 +1106,7 @@ static int select_task_rq_fair(struct task_struct *p, int sync)
                if (imbalance*this_load <= 100*load) {
                        schedstat_inc(this_sd, ttwu_move_balance);
                        schedstat_inc(p, se.nr_wakeups_passive);
-                       new_cpu = this_cpu;
-                       goto out;
+                       return this_cpu;
                }
        }
 
@@ -1111,6 +1133,10 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
                return;
        }
 
+       se->last_wakeup = se->sum_exec_runtime;
+       if (unlikely(se == pse))
+               return;
+
        cfs_rq_of(pse)->next = pse;
 
        /*