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Subject[PATCH] Prevent immediate process rescheduling
Date
Prevent the scheduler from immediately rescheduling a process
that just yielded if there is another process available.

Originally suggested by Mike Galbraith (efault@gmx.de).

Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>
---
kernel/sched_fair.c | 16 +++++++++++++++-
1 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 652e8bd..4fad08f 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -353,11 +353,25 @@ static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
{
struct rb_node *left = cfs_rq->rb_leftmost;
+ struct sched_entity *se, *curr;

if (!left)
return NULL;

- return rb_entry(left, struct sched_entity, run_node);
+ se = rb_entry(left, struct sched_entity, run_node);
+ curr = &current->se;
+
+ /*
+ * Don't select the entity who just tried to schedule away
+ * if there's another entity available.
+ */
+ if (unlikely(se == curr && cfs_rq->nr_running > 1)) {
+ struct rb_node *next_node = rb_next(&curr->run_node);
+ if (next_node)
+ se = rb_entry(next_node, struct sched_entity, run_node);
+ }
+
+ return se;
}

static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
--
1.6.0.2


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