Since we moved wakeup preemption back to virtual time, it makes sense to move
the buddy stuff back as well. The purpose of the buddy scheduling is to allow
a quickly scheduling pair of tasks to run away from the group as far as a
regular busy task would be allowed under wakeup preemption.

This has the advantage that the pair can ping-pong for a while, enjoying
cache-hotness. Without buddy scheduling other tasks would interleave destroying
the cache.

Also, it saves a word in cfs_rq.

Signed-off-by: Peter Zijlstra
---
kernel/sched.c | 1 -
kernel/sched_fair.c | 12 +++++-------
2 files changed, 5 insertions(+), 8 deletions(-)

Index: linux-2.6/kernel/sched.c
================================================== =================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -385,7 +385,6 @@ struct cfs_rq {

u64 exec_clock;
u64 min_vruntime;
- u64 pair_start;

struct rb_root tasks_timeline;
struct rb_node *rb_leftmost;
Index: linux-2.6/kernel/sched_fair.c
================================================== =================
--- linux-2.6.orig/kernel/sched_fair.c
+++ linux-2.6/kernel/sched_fair.c
@@ -790,16 +790,14 @@ set_next_entity(struct cfs_rq *cfs_rq, s
se->prev_sum_exec_runtime = se->sum_exec_runtime;
}

+static int
+wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
+
static struct sched_entity *
pick_next(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
- struct rq *rq = rq_of(cfs_rq);
- u64 pair_slice = rq->clock - cfs_rq->pair_start;
-
- if (!cfs_rq->next || pair_slice > sysctl_sched_min_granularity) {
- cfs_rq->pair_start = rq->clock;
+ if (!cfs_rq->next || wakeup_preempt_entity(cfs_rq->next, se) == 1)
return se;
- }

return cfs_rq->next;
}

--

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/