[PATCH 17/17] [DEBUG] sched/eevdf: Debug / validation crud

[Peter Zijlstra <peterz@infradead.org>]

XXX do not merge

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/sched/fair.c     |   95 ++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/sched/features.h |    2 +
 2 files changed, 97 insertions(+)

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -793,6 +793,92 @@ static inline bool min_deadline_update(s
 RB_DECLARE_CALLBACKS(static, min_deadline_cb, struct sched_entity,
 		     run_node, min_deadline, min_deadline_update);
 
+#ifdef CONFIG_SCHED_DEBUG
+struct validate_data {
+	s64 va;
+	s64 avg_vruntime;
+	s64 avg_load;
+	s64 min_deadline;
+};
+
+static void __print_se(struct cfs_rq *cfs_rq, struct sched_entity *se, int level,
+		       struct validate_data *data)
+{
+	static const char indent[] = "                                           ";
+	unsigned long weight = scale_load_down(se->load.weight);
+	struct task_struct *p = NULL;
+
+	s64 v = se->vruntime - cfs_rq->min_vruntime;
+	s64 d = se->deadline - cfs_rq->min_vruntime;
+
+	data->avg_vruntime += v * weight;
+	data->avg_load += weight;
+
+	data->min_deadline = min(data->min_deadline, d);
+
+	if (entity_is_task(se))
+		p = task_of(se);
+
+	trace_printk("%.*s%lx w: %ld ve: %Ld lag: %Ld vd: %Ld vmd: %Ld %s (%d/%s)\n",
+		     level*2, indent, (unsigned long)se,
+		     weight,
+		     v, data->va - se->vruntime, d,
+		     se->min_deadline - cfs_rq->min_vruntime,
+		     entity_eligible(cfs_rq, se) ? "E" : "N",
+		     p ? p->pid : -1,
+		     p ? p->comm : "(null)");
+}
+
+static void __print_node(struct cfs_rq *cfs_rq, struct rb_node *node, int level,
+			 struct validate_data *data)
+{
+	if (!node)
+		return;
+
+	__print_se(cfs_rq, __node_2_se(node), level, data);
+	__print_node(cfs_rq, node->rb_left, level+1, data);
+	__print_node(cfs_rq, node->rb_right, level+1, data);
+}
+
+static struct sched_entity *pick_eevdf(struct cfs_rq *cfs_rq);
+
+static void validate_cfs_rq(struct cfs_rq *cfs_rq, bool pick)
+{
+	struct sched_entity *curr = cfs_rq->curr;
+	struct rb_node *root = cfs_rq->tasks_timeline.rb_root.rb_node;
+	struct validate_data _data = {
+		.va = avg_vruntime(cfs_rq),
+		.min_deadline = (~0ULL) >> 1,
+	}, *data = &_data;
+
+	trace_printk("---\n");
+
+	__print_node(cfs_rq, root, 0, data);
+
+	trace_printk("min_deadline: %Ld avg_vruntime: %Ld / %Ld = %Ld\n",
+		     data->min_deadline,
+		     data->avg_vruntime, data->avg_load,
+		     data->avg_load ? div_s64(data->avg_vruntime, data->avg_load) : 0);
+
+	if (WARN_ON_ONCE(cfs_rq->avg_vruntime != data->avg_vruntime))
+		cfs_rq->avg_vruntime = data->avg_vruntime;
+
+	if (WARN_ON_ONCE(cfs_rq->avg_load != data->avg_load))
+		cfs_rq->avg_load = data->avg_load;
+
+	data->min_deadline += cfs_rq->min_vruntime;
+	WARN_ON_ONCE(cfs_rq->avg_load && __node_2_se(root)->min_deadline != data->min_deadline);
+
+	if (curr && curr->on_rq)
+		__print_se(cfs_rq, curr, 0, data);
+
+	if (pick)
+		trace_printk("pick: %lx\n", (unsigned long)pick_eevdf(cfs_rq));
+}
+#else
+static inline void validate_cfs_rq(struct cfs_rq *cfs_rq, bool pick) { }
+#endif
+
 /*
  * Enqueue an entity into the rb-tree:
  */
@@ -802,6 +888,9 @@ static void __enqueue_entity(struct cfs_
 	se->min_deadline = se->deadline;
 	rb_add_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline,
 				__entity_less, &min_deadline_cb);
+
+	if (sched_feat(VALIDATE_QUEUE))
+		validate_cfs_rq(cfs_rq, true);
 }
 
 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
@@ -809,6 +898,9 @@ static void __dequeue_entity(struct cfs_
 	rb_erase_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline,
 				  &min_deadline_cb);
 	avg_vruntime_sub(cfs_rq, se);
+
+	if (sched_feat(VALIDATE_QUEUE))
+		validate_cfs_rq(cfs_rq, true);
 }
 
 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
@@ -894,6 +986,9 @@ static struct sched_entity *pick_eevdf(s
 	if (unlikely(!best)) {
 		struct sched_entity *left = __pick_first_entity(cfs_rq);
 		if (left) {
+			trace_printk("EEVDF scheduling fail, picking leftmost\n");
+			validate_cfs_rq(cfs_rq, false);
+			tracing_off();
 			pr_err("EEVDF scheduling fail, picking leftmost\n");
 			return left;
 		}
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -6,6 +6,8 @@ SCHED_FEAT(PLACE_DEADLINE_INITIAL, true)
 
 SCHED_FEAT(MINIMAL_VA, false)
 
+SCHED_FEAT(VALIDATE_QUEUE, false)
+
 /*
  * Prefer to schedule the task we woke last (assuming it failed
  * wakeup-preemption), since its likely going to consume data we