sched: sync wakeups vs avg_overlap

While looking at the code I wondered why we always do:

  sync && avg_overlap < migration_cost

Which is a bit odd, since the overlap test was meant to detect sync wakeups
so using it to specialize sync wakeups doesn't make much sense.

Hence change the code to do:

  sync || avg_overlap < migration_cost

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 10 insertions, 8 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index fcbe850a5a90..18fd17172eb6 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1103,6 +1103,11 @@ wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
         if (!(this_sd->flags & SD_WAKE_AFFINE) || !sched_feat(AFFINE_WAKEUPS))
                 return 0;
 
+        if (!sync && sched_feat(SYNC_WAKEUPS) &&
+            curr->se.avg_overlap < sysctl_sched_migration_cost &&
+            p->se.avg_overlap < sysctl_sched_migration_cost)
+                sync = 1;
+
         /*
          * If sync wakeup then subtract the (maximum possible)
          * effect of the currently running task from the load
@@ -1127,11 +1132,8 @@ wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
          * a reasonable amount of time then attract this newly
          * woken task:
          */
-        if (sync && balanced) {
-                if (curr->se.avg_overlap < sysctl_sched_migration_cost &&
-                    p->se.avg_overlap < sysctl_sched_migration_cost)
-                        return 1;
-        }
+        if (sync && balanced)
+                return 1;
 
         schedstat_inc(p, se.nr_wakeups_affine_attempts);
         tl_per_task = cpu_avg_load_per_task(this_cpu);
@@ -1268,9 +1270,9 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
         if (!sched_feat(WAKEUP_PREEMPT))
                 return;
 
-        if (sched_feat(WAKEUP_OVERLAP) && sync &&
-                        se->avg_overlap < sysctl_sched_migration_cost &&
-                        pse->avg_overlap < sysctl_sched_migration_cost) {
+        if (sched_feat(WAKEUP_OVERLAP) && (sync ||
+                        (se->avg_overlap < sysctl_sched_migration_cost &&
+                         pse->avg_overlap < sysctl_sched_migration_cost))) {
                 resched_task(curr);
                 return;
         }