[PATCH v2 8/8] sched/fair: use utilization to select misfit task

[Vincent Guittot <vincent.guittot@linaro.org>]

utilization is used to detect a misfit task but the load is then used to
select the task on the CPU which can lead to select a small task with
high weight instead of the task that triggered the misfit migration.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
 kernel/sched/fair.c  | 28 ++++++++++++++--------------
 kernel/sched/sched.h |  2 +-
 2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 53e64a7..d08cc12 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3817,16 +3817,16 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
 		return;
 
 	if (!p) {
-		rq->misfit_task_load = 0;
+		rq->misfit_task_util = 0;
 		return;
 	}
 
 	if (task_fits_capacity(p, capacity_of(cpu_of(rq)))) {
-		rq->misfit_task_load = 0;
+		rq->misfit_task_util = 0;
 		return;
 	}
 
-	rq->misfit_task_load = task_h_load(p);
+	rq->misfit_task_util = task_util_est(p);
 }
 
 #else /* CONFIG_SMP */
@@ -7487,14 +7487,14 @@ static int detach_tasks(struct lb_env *env)
 			break;
 
 		case migrate_misfit:
-			load = task_h_load(p);
+			util = task_util_est(p);
 
 			/*
 			 * utilization of misfit task might decrease a bit
 			 * since it has been recorded. Be conservative in the
 			 * condition.
 			 */
-			if (load < env->imbalance)
+			if (2*util < env->imbalance)
 				goto next;
 
 			env->imbalance = 0;
@@ -7785,7 +7785,7 @@ struct sg_lb_stats {
 	unsigned int group_weight;
 	enum group_type group_type;
 	unsigned int group_asym_capacity; /* tasks should be move to preferred cpu */
-	unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
+	unsigned long group_misfit_task_util; /* A CPU has a task too big for its capacity */
 #ifdef CONFIG_NUMA_BALANCING
 	unsigned int nr_numa_running;
 	unsigned int nr_preferred_running;
@@ -7959,7 +7959,7 @@ check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
  */
 static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd)
 {
-	return rq->misfit_task_load &&
+	return rq->misfit_task_util &&
 		(rq->cpu_capacity_orig < rq->rd->max_cpu_capacity ||
 		 check_cpu_capacity(rq, sd));
 }
@@ -8078,7 +8078,7 @@ group_type group_classify(struct lb_env *env,
 	if (sgs->group_asym_capacity)
 		return group_asym_capacity;
 
-	if (sgs->group_misfit_task_load)
+	if (sgs->group_misfit_task_util)
 		return group_misfit_task;
 
 	if (!group_has_capacity(env, sgs))
@@ -8164,8 +8164,8 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 
 		/* Check for a misfit task on the cpu */
 		if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
-		    sgs->group_misfit_task_load < rq->misfit_task_load) {
-			sgs->group_misfit_task_load = rq->misfit_task_load;
+		    sgs->group_misfit_task_util < rq->misfit_task_util) {
+			sgs->group_misfit_task_util = rq->misfit_task_util;
 			*sg_status |= SG_OVERLOAD;
 		}
 	}
@@ -8261,7 +8261,7 @@ static bool update_sd_pick_busiest(struct lb_env *env,
 		 * If we have more than one misfit sg go with the
 		 * biggest misfit.
 		 */
-		if (sgs->group_misfit_task_load < busiest->group_misfit_task_load)
+		if (sgs->group_misfit_task_util < busiest->group_misfit_task_util)
 			return false;
 		break;
 
@@ -8458,7 +8458,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
 	if (busiest->group_type == group_misfit_task) {
 		/* Set imbalance to allow misfit task to be balanced. */
 		env->balance_type = migrate_misfit;
-		env->imbalance = busiest->group_misfit_task_load;
+		env->imbalance = busiest->group_misfit_task_util;
 		return;
 	}
 
@@ -8801,8 +8801,8 @@ static struct rq *find_busiest_queue(struct lb_env *env,
 			 * For ASYM_CPUCAPACITY domains with misfit tasks we simply
 			 * seek the "biggest" misfit task.
 			 */
-			if (rq->misfit_task_load > busiest_load) {
-				busiest_load = rq->misfit_task_load;
+			if (rq->misfit_task_util > busiest_util) {
+				busiest_util = rq->misfit_task_util;
 				busiest = rq;
 			}
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 7583fad..ef6e1b2 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -916,7 +916,7 @@ struct rq {
 
 	unsigned char		idle_balance;
 
-	unsigned long		misfit_task_load;
+	unsigned long		misfit_task_util;
 
 	/* For active balancing */
 	int			active_balance;
-- 
2.7.4