[tip: sched/core] sched/eevdf: Fixup PELT vs DELAYED_DEQUEUE

tip-bot2 for Peter Zijlstra
2024-08-18T06:23:09Z

The following commit has been merged into the sched/core branch of tip:

Commit-ID: fc1892becd5672f52329a75c73117b60ac7841b7
Gitweb: https://git.kernel.org/tip/fc1892becd5672f52329a75c73117b60ac7841b7
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 26 Apr 2024 13:00:50 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Sat, 17 Aug 2024 11:06:45 +02:00

sched/eevdf: Fixup PELT vs DELAYED_DEQUEUE

Note that tasks that are kept on the runqueue to burn off negative
lag, are not in fact runnable anymore, they'll get dequeued the moment
they get picked.

As such, don't count this time towards runnable.

Thanks to Valentin for spotting I had this backwards initially.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105030.514088302@infradead.org
---
kernel/sched/fair.c | 2 ++
kernel/sched/sched.h | 6 ++++++
2 files changed, 8 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1a59339..0eb1bbf 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5402,6 +5402,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
!entity_eligible(cfs_rq, se)) {
if (cfs_rq->next == se)
cfs_rq->next = NULL;
+ update_load_avg(cfs_rq, se, 0);
se->sched_delayed = 1;
return false;
}
@@ -6841,6 +6842,7 @@ requeue_delayed_entity(struct sched_entity *se)
}
}

+ update_load_avg(cfs_rq, se, 0);
se->sched_delayed = 0;
}

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 263b4de..2f5d658 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -820,6 +820,9 @@ static inline void se_update_runnable(struct sched_entity *se)

static inline long se_runnable(struct sched_entity *se)
{
+ if (se->sched_delayed)
+ return false;
+
if (entity_is_task(se))
return !!se->on_rq;
else
@@ -834,6 +837,9 @@ static inline void se_update_runnable(struct sched_entity *se) { }

static inline long se_runnable(struct sched_entity *se)
{
+ if (se->sched_delayed)
+ return false;
+
return !!se->on_rq;
}