Re: [PATCH v5 6/7] sched/deadline: Deferrable dl server

[Daniel Bristot de Oliveira <bristot@kernel.org>]

> The code is not doing what I intended because I thought it was doing overload
> control on the replenishment, but it is not (my bad).
> 

I am still testing but... it is missing something like this (famous last words).

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 1092ca8892e0..6e2d21c47a04 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -842,6 +842,8 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
  * runtime, or it just underestimated it during sched_setattr().
  */
 static int start_dl_timer(struct sched_dl_entity *dl_se);
+static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t);
+
 static void replenish_dl_entity(struct sched_dl_entity *dl_se)
 {
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
@@ -852,9 +854,18 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
 	/*
 	 * This could be the case for a !-dl task that is boosted.
 	 * Just go with full inherited parameters.
+	 *
+	 * Or, it could be the case of a zerolax reservation that
+	 * was not able to consume its runtime in background and
+	 * reached this point with current u > U.
+	 *
+	 * In both cases, set a new period.
 	 */
-	if (dl_se->dl_deadline == 0)
-		replenish_dl_new_period(dl_se, rq);
+	if (dl_se->dl_deadline == 0 ||
+		(dl_se->dl_zerolax_armed && dl_entity_overflow(dl_se, rq_clock(rq)))) {
+			dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
+			dl_se->runtime = pi_of(dl_se)->dl_runtime;
+	}

 	if (dl_se->dl_yielded && dl_se->runtime > 0)
 		dl_se->runtime = 0;