Re: [announce] CFS-devel, performance improvements

Peter Zijlstra
2007-09-13T19:09:24Z

On Thu, 2007-09-13 at 14:28 -0400, Kyle Moffett wrote:

> with the exception of one patch that's missing a changelog entry.

Ah, that would have been one of mine.

---
From: Peter Zijlstra <a.p.zijlstra@chello.nl>

Handle vruntime overflow by centering the key space around min_vruntime.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/sched_fair.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index a306f05..b8e2a0d 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -116,11 +116,18 @@ set_leftmost(struct cfs_rq *cfs_rq, struct rb_node *leftmost)
cfs_rq->rb_leftmost = leftmost;
if (leftmost) {
se = rb_entry(leftmost, struct sched_entity, run_node);
- cfs_rq->min_vruntime = max(se->vruntime,
- cfs_rq->min_vruntime);
+ if ((se->vruntime > cfs_rq->min_vruntime) ||
+ (cfs_rq->min_vruntime > (1ULL << 61) &&
+ se->vruntime < (1ULL << 50)))
+ cfs_rq->min_vruntime = se->vruntime;
}
}

+s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ return se->fair_key - cfs_rq->min_vruntime;
+}
+
/*
* Enqueue an entity into the rb-tree:
*/
@@ -130,7 +137,7 @@ __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
struct rb_node *parent = NULL;
struct sched_entity *entry;
- s64 key = se->fair_key;
+ s64 key = entity_key(cfs_rq, se);
int leftmost = 1;

/*
@@ -143,7 +150,7 @@ __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
* We dont care about collisions. Nodes with
* the same key stay together.
*/
- if (key - entry->fair_key < 0) {
+ if (key < entity_key(cfs_rq, entry)) {
link = &parent->rb_left;
} else {
link = &parent->rb_right;