Hi Ingo,
The follow patch applies to sched-devel. I know the original function was
somehow trying to protect against dequeueing by pre-iterating. I am not sure
if I captured the intent properly in that regard. What I can say is that the
old algorithm would miss tasks, and that is now fixed. It may need further
adjustment if I missed the pre-iterating operation.
Hi Peter,
I was wrong earlier when I mentioned there might be a problem with
entity_is_task(). I think this was the root cause of what I was seeing.
Sorry for the red-herring.
Regards,
-Greg
-----------------------
sched: fix SCHED_OTHER balance iterator to include all tasks
The currently logic inadvertently skips the last task on the run-queue,
resulting in missed balance opportunities.
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: David Bahi <dbahi@novell.com>
CC: Ingo Molnar <mingo@elte.hu>
CC: Peter Zijlstra <peterz@infradead.org>
---
kernel/sched_fair.c | 19 +++++++------------
1 files changed, 7 insertions(+), 12 deletions(-)
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 87b7300..e8c289a 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1700,23 +1700,18 @@ __load_balance_iterator(struct cfs_rq *cfs_rq, struct list_head *next)
struct task_struct *p = NULL;
struct sched_entity *se;
- if (next == &cfs_rq->tasks)
- return NULL;
-
- /* Skip over entities that are not tasks */
- do {
+ while (next != &cfs_rq->tasks) {
se = list_entry(next, struct sched_entity, group_node);
next = next->next;
- } while (next != &cfs_rq->tasks && !entity_is_task(se));
- if (next == &cfs_rq->tasks)
- return NULL;
+ /* Skip over entities that are not tasks */
+ if (entity_is_task(se)) {
+ p = task_of(se);
+ break;
+ }
+ }
cfs_rq->balance_iterator = next;
-
- if (entity_is_task(se))
- p = task_of(se);
-
return p;
}
--
