linux-kernel - [PATCH v2 5/7] sched/fair: Employ capacity_greater() throughout load

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Date:   Fri, 19 Feb 2021 13:00:01 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Qais Yousef <qais.yousef@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Quentin Perret <qperret@...gle.com>,
        Pavan Kondeti <pkondeti@...eaurora.org>,
        Rik van Riel <riel@...riel.com>,
        Lingutla Chandrasekhar <clingutla@...eaurora.org>
Subject: [PATCH v2 5/7] sched/fair: Employ capacity_greater() throughout load_balance()

While at it, replace group_smaller_{min, max}_cpu_capacity() with
comparisons of the source group's min/max capacity and the destination
CPU's capacity.

Reviewed-by: Qais Yousef <qais.yousef@....com>
Signed-off-by: Valentin Schneider <valentin.schneider@....com>
---
 kernel/sched/fair.c | 33 ++++-----------------------------
 1 file changed, 4 insertions(+), 29 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index cc16d0e0b9fb..af5ce083c982 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8320,26 +8320,6 @@ group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
 	return false;
 }
 
-/*
- * group_smaller_min_cpu_capacity: Returns true if sched_group sg has smaller
- * per-CPU capacity than sched_group ref.
- */
-static inline bool
-group_smaller_min_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
-{
-	return fits_capacity(sg->sgc->min_capacity, ref->sgc->min_capacity);
-}
-
-/*
- * group_smaller_max_cpu_capacity: Returns true if sched_group sg has smaller
- * per-CPU capacity_orig than sched_group ref.
- */
-static inline bool
-group_smaller_max_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
-{
-	return fits_capacity(sg->sgc->max_capacity, ref->sgc->max_capacity);
-}
-
 static inline enum
 group_type group_classify(unsigned int imbalance_pct,
 			  struct sched_group *group,
@@ -8491,15 +8471,10 @@ static bool update_sd_pick_busiest(struct lb_env *env,
 	if (!sgs->sum_h_nr_running)
 		return false;
 
-	/*
-	 * Don't try to pull misfit tasks we can't help.
-	 * We can use max_capacity here as reduction in capacity on some
-	 * CPUs in the group should either be possible to resolve
-	 * internally or be covered by avg_load imbalance (eventually).
-	 */
+	/* Don't try to pull misfit tasks we can't help */
 	if (static_branch_unlikely(&sched_asym_cpucapacity) &&
 	    sgs->group_type == group_misfit_task &&
-	    (!group_smaller_max_cpu_capacity(sg, sds->local) ||
+	    (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) ||
 	     sds->local_stat.group_type != group_has_spare))
 		return false;
 
@@ -8583,7 +8558,7 @@ static bool update_sd_pick_busiest(struct lb_env *env,
 	 */
 	if (sd_has_asym_cpucapacity(env->sd) &&
 	    (sgs->group_type <= group_fully_busy) &&
-	    (group_smaller_min_cpu_capacity(sds->local, sg)))
+	    (capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu))))
 		return false;
 
 	return true;
@@ -9396,7 +9371,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
 		 * average load.
 		 */
 		if (sd_has_asym_cpucapacity(env->sd) &&
-		    capacity_of(env->dst_cpu) < capacity &&
+		    !capacity_greater(capacity_of(env->dst_cpu), capacity) &&
 		    nr_running == 1)
 			continue;
 
-- 
2.27.0