sched: revert recent sync wakeup changes
Peter Zijlstra [Wed, 11 Feb 2009 13:27:17 +0000 (14:27 +0100)]
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>

kernel/sched.c
kernel/sched_fair.c

index e1fc67d..f11c02b 100644 (file)
@@ -2266,16 +2266,6 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
        if (!sched_feat(SYNC_WAKEUPS))
                sync = 0;
 
-       if (!sync) {
-               if (current->se.avg_overlap < sysctl_sched_migration_cost &&
-                         p->se.avg_overlap < sysctl_sched_migration_cost)
-                       sync = 1;
-       } else {
-               if (current->se.avg_overlap >= sysctl_sched_migration_cost ||
-                         p->se.avg_overlap >= sysctl_sched_migration_cost)
-                       sync = 0;
-       }
-
 #ifdef CONFIG_SMP
        if (sched_feat(LB_WAKEUP_UPDATE)) {
                struct sched_domain *sd;
index a7e50ba..0566f2a 100644 (file)
@@ -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;
        }