sched: revert recent sync wakeup changes

Intel reported a 10% regression (mysql+sysbench) on a 16-way machine
with these patches:

  1596e29: sched: symmetric sync vs avg_overlap
  d942fb6: sched: fix sync wakeups

Revert them.

Reported-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Bisected-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 2 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index a7e50ba185ac..0566f2a03c42 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1191,15 +1191,20 @@ wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
             int idx, unsigned long load, unsigned long this_load,
             unsigned int imbalance)
 {
+        struct task_struct *curr = this_rq->curr;
+        struct task_group *tg;
         unsigned long tl = this_load;
         unsigned long tl_per_task;
-        struct task_group *tg;
         unsigned long weight;
         int balanced;
 
         if (!(this_sd->flags & SD_WAKE_AFFINE) || !sched_feat(AFFINE_WAKEUPS))
                 return 0;
 
+        if (sync && (curr->se.avg_overlap > sysctl_sched_migration_cost ||
+                        p->se.avg_overlap > sysctl_sched_migration_cost))
+                sync = 0;
+
         /*
          * If sync wakeup then subtract the (maximum possible)
          * effect of the currently running task from the load
@@ -1426,7 +1431,9 @@ 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) {
+        if (sched_feat(WAKEUP_OVERLAP) && (sync ||
+                        (se->avg_overlap < sysctl_sched_migration_cost &&
+                         pse->avg_overlap < sysctl_sched_migration_cost))) {
                 resched_task(curr);
                 return;
         }