check_prempt_wakeup_fair is checking whether the current task has to be
preempted by the newly wake-up task. To avoid multiple swaps the logic
is decided as if the wake-up task is the best task then only preempt the
current task.
In CFS time, getting the best task was as simple as piking the left-most
node. But in EEVDF non-fast path, the entire tree has to be traversed in
a worst case scenario.
So, IMHO let's first check the newly wake-up task is eligible before
searching for the best task.
Signed-off-by: Balakumaran Kannan <[email protected]>
---
Changes in v2:
- Fixed the commit message with proper name and Signed-off-by
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 533547e3c90a..8d810d6a2cb7 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8334,7 +8334,7 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
/*
* XXX pick_eevdf(cfs_rq) != se ?
*/
- if (pick_eevdf(cfs_rq) == pse)
+ if (entity_eligible(cfs_rq, pse) && (pick_eevdf(cfs_rq) == pse))
goto preempt;
return;
--
2.33.8