[PATCH] sched/eevdf: Toggle eligibility through sched_feat

[Youssef Esmat]

Interactive workloads see performance gains by disabling eligibility
checks (EEVDF->EVDF). Disabling the checks reduces the number of
context switches and delays less important work (higher deadlines/nice
values) in favor of more important work (lower deadlines/nice values).

That said, that can add large latencies for some work loads and as the
default is eligibility on, but allowing it to be turned off when
beneficial.

Signed-off-by: Youssef Esmat <youssefesmat@xxxxxxxxxxxx>
Link: https://lore.kernel.org/lkml/CA+q576MS0-MV1Oy-eecvmYpvNT3tqxD8syzrpxQ-Zk310hvRbw@xxxxxxxxxxxxxx/
---
 kernel/sched/fair.c     | 3 +++
 kernel/sched/features.h | 1 +
 2 files changed, 4 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a751e552f253..16106da5a354 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -728,6 +728,9 @@ int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se)
 	s64 avg = cfs_rq->avg_vruntime;
 	long load = cfs_rq->avg_load;
 
+	if (!sched_feat(ENFORCE_ELIGIBILITY))
+		return 1;
+
 	if (curr && curr->on_rq) {
 		unsigned long weight = scale_load_down(curr->load.weight);
 
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index f770168230ae..84e38a0045b7 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -7,6 +7,7 @@
 SCHED_FEAT(PLACE_LAG, true)
 SCHED_FEAT(PLACE_DEADLINE_INITIAL, true)
 SCHED_FEAT(RUN_TO_PARITY, true)
+SCHED_FEAT(ENFORCE_ELIGIBILITY, true)
 
 /*
  * Prefer to schedule the task we woke last (assuming it failed
-- 
2.42.0.655.g421f12c284-goog