Re: [PATCH -v8a 3/7] sched: use a buddy to implement yield_task_fair

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

On Tue, 2011-02-01 at 09:51 -0500, Rik van Riel wrote:
> -static void yield_task_fair(struct rq *rq)
> -{
> -       struct task_struct *curr = rq->curr;
> -       struct cfs_rq *cfs_rq = task_cfs_rq(curr);
> -       struct sched_entity *rightmost, *se = &curr->se;
> -
> -       /*
> -        * Are we the only task in the tree?
> -        */
> -       if (unlikely(rq->nr_running == 1))
> -               return;
> -
> -       clear_buddies(cfs_rq, se);
> -
> -       if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
> -               update_rq_clock(rq);
> -               /*
> -                * Update run-time statistics of the 'current'.
> -                */
> -               update_curr(cfs_rq);
> -
> -               return;
> -       }
> -       /*
> -        * Find the rightmost entry in the rbtree:
> -        */
> -       rightmost = __pick_last_entity(cfs_rq);
> -       /*
> -        * Already in the rightmost position?
> -        */
> -       if (unlikely(!rightmost || entity_before(rightmost, se)))
> -               return;
> -
> -       /*
> -        * Minimally necessary key value to be last in the tree:
> -        * Upon rescheduling, sched_class::put_prev_task() will place
> -        * 'current' within the tree based on its new key value.
> -        */
> -       se->vruntime = rightmost->vruntime + 1;
> -} 


This also wants the below bit in order to build without warnings for
SCHED_DEBUG=n:


---
Index: linux-2.6/kernel/sched_fair.c
===================================================================
--- linux-2.6.orig/kernel/sched_fair.c
+++ linux-2.6/kernel/sched_fair.c
@@ -431,6 +431,7 @@ static struct sched_entity *__pick_next_
 	return rb_entry(next, struct sched_entity, run_node);
 }
 
+#ifdef CONFIG_SCHED_DEBUG
 static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
 {
 	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
@@ -445,7 +446,6 @@ static struct sched_entity *__pick_last_
  * Scheduling class statistics methods:
  */
 
-#ifdef CONFIG_SCHED_DEBUG
 int sched_proc_update_handler(struct ctl_table *table, int write,
 		void __user *buffer, size_t *lenp,
 		loff_t *ppos)