sched: affine sync wakeups

make sync wakeups affine for cache-cold tasks: if a cache-cold task
is woken up by a sync wakeup then use the opportunity to migrate it
straight away. (the two tasks are 'related' because they communicate)

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 1 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 5a91fe0b5de6..7fd343462597 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1521,6 +1521,12 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
                         unsigned long tl = this_load;
                         unsigned long tl_per_task;
 
+                        /*
+                         * Attract cache-cold tasks on sync wakeups:
+                         */
+                        if (sync && !task_hot(p, rq->clock, this_sd))
+                                goto out_set_cpu;
+
                         schedstat_inc(p, se.nr_wakeups_affine_attempts);
                         tl_per_task = cpu_avg_load_per_task(this_cpu);
 
@@ -1598,7 +1604,7 @@ out_activate:
          * the waker guarantees that the freshly woken up task is going
          * to be considered on this CPU.)
          */
-        if (!sync || cpu != this_cpu)
+        if (!sync || rq->curr == rq->idle)
                 check_preempt_curr(rq, p);
         success = 1;