The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: d68803506ffb4f72cbeaea94a3a745a6faf62bdd
Gitweb: https://git.kernel.org/tip/d68803506ffb4f72cbeaea94a3a745a6faf62bdd
Author: Mike Galbraith <efault@xxxxxx>
AuthorDate: Fri, 08 Nov 2024 01:24:35 +01:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 11 Nov 2024 11:49:44 +01:00
sched/fair: Dequeue sched_delayed tasks when waking to a busy CPU
Phil Auld (Redhat) reported an fio benchmark regression having been found
to have been caused by addition of the DELAY_DEQUEUE feature, suggested it
may be related to wakees losing the ability to migrate, and confirmed that
restoration of same indeed did restore previous performance.
(de-uglified-a-lot-by)
Fixes: 152e11f6df29 ("sched/fair: Implement delayed dequeue")
Reported-by: Phil Auld <pauld@xxxxxxxxxx>
Suggested-by: Phil Auld <pauld@xxxxxxxxxx>
Reviewed-by: Phil Auld <pauld@xxxxxxxxxx>
Tested-by: Jirka Hladky <jhladky@xxxxxxxxxx>
Signed-off-by: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/lkml/20241101124715.GA689589@pauld.westford.=
kernel/sched/core.c | 48 +++++++++++++++++++++++++++++-------------------
kernel/sched/sched.h | 5 +++++
2 files changed, 34 insertions(+), 19 deletions(-)
---
kernel/sched/core.c | 46 ++++++++++++++++++++++++++-----------------
kernel/sched/sched.h | 5 +++++-
2 files changed, 33 insertions(+), 18 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 719e0ed..b35752f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3734,28 +3734,38 @@ ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
*/
static int ttwu_runnable(struct task_struct *p, int wake_flags)
{
- struct rq_flags rf;
- struct rq *rq;
- int ret = 0;
+ CLASS(__task_rq_lock, rq_guard)(p);
+ struct rq *rq = rq_guard.rq;
- rq = __task_rq_lock(p, &rf);
- if (task_on_rq_queued(p)) {
- update_rq_clock(rq);
- if (p->se.sched_delayed)
- enqueue_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_DELAYED);
- if (!task_on_cpu(rq, p)) {
- /*
- * When on_rq && !on_cpu the task is preempted, see if
- * it should preempt the task that is current now.
- */
- wakeup_preempt(rq, p, wake_flags);
+ if (!task_on_rq_queued(p))
+ return 0;
+
+ update_rq_clock(rq);
+ if (p->se.sched_delayed) {
+ int queue_flags = ENQUEUE_DELAYED | ENQUEUE_NOCLOCK;
+
+ /*
+ * Since sched_delayed means we cannot be current anywhere,
+ * dequeue it here and have it fall through to the
+ * select_task_rq() case further along the ttwu() path.
+ */
+ if (rq->nr_running > 1 && p->nr_cpus_allowed > 1) {
+ dequeue_task(rq, p, DEQUEUE_SLEEP | queue_flags);
+ return 0;
}
- ttwu_do_wakeup(p);
- ret = 1;
+
+ enqueue_task(rq, p, queue_flags);
}
- __task_rq_unlock(rq, &rf);
+ if (!task_on_cpu(rq, p)) {
+ /*
+ * When on_rq && !on_cpu the task is preempted, see if
+ * it should preempt the task that is current now.
+ */
+ wakeup_preempt(rq, p, wake_flags);
+ }
+ ttwu_do_wakeup(p);
- return ret;
+ return 1;
}
#ifdef CONFIG_SMP
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 6c54a57..97f7936 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1779,6 +1779,11 @@ task_rq_unlock(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
}
+DEFINE_LOCK_GUARD_1(__task_rq_lock, struct task_struct,
+ _T->rq = __task_rq_lock(_T->lock, &_T->rf),
+ __task_rq_unlock(_T->rq, &_T->rf),
+ struct rq *rq; struct rq_flags rf)
+
DEFINE_LOCK_GUARD_1(task_rq_lock, struct task_struct,
_T->rq = task_rq_lock(_T->lock, &_T->rf),
task_rq_unlock(_T->rq, _T->lock, &_T->rf),
|