[PATCH 7/8] sched/eevdf: Compare min slice during wake_affine

[Vincent Guittot]

Add a new level in wake affine where we check on which CPU the task
would most probably run 1st between this and prev CPUs.

Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
---
 kernel/sched/fair.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a01a88dde811..452da94289fe 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8402,6 +8402,9 @@ static int wake_wide(struct task_struct *p)
  * wake_affine_idle() - only considers 'now', it check if the waking CPU is
  *			cache-affine and is (or	will be) idle.
  *
+ * wake_affine_slice() - only considers 'now', it check if the waking CPU can
+ *			 be preempted because using longer slice.
+ *
  * wake_affine_weight() - considers the weight to reflect the average
  *			  scheduling latency of the CPUs. This seems to work
  *			  for the overloaded case.
@@ -8437,6 +8440,20 @@ wake_affine_idle(int this_cpu, int prev_cpu, int sync)
 	return nr_cpumask_bits;
 }
 
+static int
+wake_affine_slice(struct task_struct *p, int this_cpu, int prev_cpu)
+{
+	struct sched_entity *se = &p->se;
+
+	if (se->slice < get_rq_min_slice(cpu_rq(prev_cpu)))
+		return prev_cpu;
+
+	if (se->slice < get_rq_min_slice(cpu_rq(this_cpu)))
+		return this_cpu;
+
+	return nr_cpumask_bits;
+}
+
 static int
 wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
 		   int this_cpu, int prev_cpu, int sync)
@@ -8488,6 +8505,9 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p,
 	if (sched_feat(WA_IDLE))
 		target = wake_affine_idle(this_cpu, prev_cpu, sync);
 
+	if (sched_feat(PREEMPT_SHORT) && target == nr_cpumask_bits)
+		target = wake_affine_slice(p, this_cpu, prev_cpu);
+
 	if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
 		target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
 
-- 
2.53.0