[RFC PATCH 4/6] sched/dl: Improve capacity-aware wakeup

[Luca Abeni]

From: luca abeni <luca.abeni@xxxxxxxxxxxxxxx>

Instead of considering the "static CPU bandwidth" allocated to
a SCHED_DEADLINE task (ratio between its maximum runtime and
reservation period), try to use the remaining runtime and time
to scheduling deadline.

Signed-off-by: luca abeni <luca.abeni@xxxxxxxxxxxxxxx>
---
 kernel/sched/cpudeadline.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index d21f7905b9c1..111dd9ac837b 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -114,8 +114,13 @@ static inline int dl_task_fit(const struct sched_dl_entity *dl_se,
 			      int cpu, u64 *c)
 {
 	u64 cap = (arch_scale_cpu_capacity(NULL, cpu) * arch_scale_freq_capacity(cpu)) >> SCHED_CAPACITY_SHIFT;
-	s64 rel_deadline = dl_se->dl_deadline;
-	u64 rem_runtime  = dl_se->dl_runtime;
+	s64 rel_deadline = dl_se->deadline - sched_clock_cpu(smp_processor_id());
+	u64 rem_runtime  = dl_se->runtime;
+
+	if ((rel_deadline < 0) || (rel_deadline * dl_se->dl_runtime < dl_se->dl_deadline * rem_runtime)) {
+		rel_deadline = dl_se->dl_deadline;
+		rem_runtime  = dl_se->dl_runtime;
+	}
 
 	if (c)
 		*c = cap;
-- 
2.20.1