[PATCH v2 06/22] sched/fair: Collect load-balancing stats for IPC classes

[Ricardo Neri]

When selecting a busiest scheduling group, the IPC class of the current
task can be used to select between two scheduling groups of equal
asym_packing priority and number of running tasks.

Compute a new IPC class performance score for a scheduling group. It
is the sum of the performance of the current tasks of all the runqueues.

Also, keep track of the task with the lowest IPC class score on the
scheduling group.

These two metrics will be used during idle load balancing to compute the
current and the prospective task-class performance of a scheduling
group.

Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Cc: Len Brown <len.brown@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Tim C. Chen <tim.c.chen@xxxxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: linux-pm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
---
Changes since v1:
 * Implemented cleanups and reworks from PeterZ. Thanks!
 * Used the new interface names.
---
 kernel/sched/fair.c | 55 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 224107278471..3a1d6c50a19b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9100,6 +9100,57 @@ group_type group_classify(unsigned int imbalance_pct,
 	return group_has_spare;
 }
 
+struct sg_lb_ipcc_stats {
+	int min_score;	/* Min(score(rq->curr->ipcc)) */
+	int min_ipcc;	/* Min(rq->curr->ipcc) */
+	long sum_score; /* Sum(score(rq->curr->ipcc)) */
+};
+
+#ifdef CONFIG_IPC_CLASSES
+static void init_rq_ipcc_stats(struct sg_lb_ipcc_stats *sgcs)
+{
+	*sgcs = (struct sg_lb_ipcc_stats) {
+		.min_score = INT_MAX,
+	};
+}
+
+/** Called only if cpu_of(@rq) is not idle and has tasks running. */
+static void update_sg_lb_ipcc_stats(struct sg_lb_ipcc_stats *sgcs,
+				    struct rq *rq)
+{
+	struct task_struct *curr;
+	unsigned short ipcc;
+	int score;
+
+	if (!sched_ipcc_enabled())
+		return;
+
+	curr = rcu_dereference(rq->curr);
+	if (!curr || (curr->flags & PF_EXITING) || is_idle_task(curr))
+		return;
+
+	ipcc = curr->ipcc;
+	score = arch_get_ipcc_score(ipcc, cpu_of(rq));
+
+	sgcs->sum_score += score;
+
+	if (score < sgcs->min_score) {
+		sgcs->min_score = score;
+		sgcs->min_ipcc = ipcc;
+	}
+}
+
+#else /* CONFIG_IPC_CLASSES */
+static void update_sg_lb_ipcc_stats(struct sg_lb_ipcc_stats *sgcs,
+				    struct rq *rq)
+{
+}
+
+static void init_rq_ipcc_stats(struct sg_lb_ipcc_stats *class_sgs)
+{
+}
+#endif /* CONFIG_IPC_CLASSES */
+
 /**
  * asym_smt_can_pull_tasks - Check whether the load balancing CPU can pull tasks
  * @dst_cpu:	Destination CPU of the load balancing
@@ -9212,9 +9263,11 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 				      struct sg_lb_stats *sgs,
 				      int *sg_status)
 {
+	struct sg_lb_ipcc_stats sgcs;
 	int i, nr_running, local_group;
 
 	memset(sgs, 0, sizeof(*sgs));
+	init_rq_ipcc_stats(&sgcs);
 
 	local_group = group == sds->local;
 
@@ -9264,6 +9317,8 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 			if (sgs->group_misfit_task_load < load)
 				sgs->group_misfit_task_load = load;
 		}
+
+		update_sg_lb_ipcc_stats(&sgcs, rq);
 	}
 
 	sgs->group_capacity = group->sgc->capacity;
-- 
2.25.1