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sched: handle vruntime 64-bit overflow 

Handle vruntime overflow by centering the key space around min_vruntime.

( otherwise we could overflow 64-bit vruntime in a few days with SCHED_IDLE
 tasks - or in a few years with nice +19. )

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Peter Zijlstra 2007-10-15 17:00:05 +02:00 committed by Ingo Molnar
parent 94dfb5e75e
commit 9014623c0e
1 changed files with 11 additions and 4 deletions
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15
kernel/sched_fair.c
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@ -124,11 +124,18 @@ 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:
*/
@ -138,7 +145,7 @@ __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;
/*
@ -151,7 +158,7 @@ __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;