linux-kernel - [tip: sched/core] sched/fair: Use rq->nr

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Date:   Mon, 21 Oct 2019 09:12:43 -0000
From:   "tip-bot2 for Vincent Guittot" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Ben Segall <bsegall@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Mike Galbraith <efault@....de>,
        Morten.Rasmussen@....com, Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>, hdanton@...a.com,
        parth@...ux.ibm.com, pauld@...hat.com, quentin.perret@....com,
        riel@...riel.com, srikar@...ux.vnet.ibm.com,
        valentin.schneider@....com, Ingo Molnar <mingo@...nel.org>,
        Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/fair: Use rq->nr_running when balancing load

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     5e23e474431529b7d1480f649ce33d0e9c1b2e48
Gitweb:        https://git.kernel.org/tip/5e23e474431529b7d1480f649ce33d0e9c1b2e48
Author:        Vincent Guittot <vincent.guittot@...aro.org>
AuthorDate:    Fri, 18 Oct 2019 15:26:32 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Mon, 21 Oct 2019 09:40:54 +02:00

sched/fair: Use rq->nr_running when balancing load

CFS load_balance() only takes care of CFS tasks whereas CPUs can be used by
other scheduling classes. Typically, a CFS task preempted by an RT or deadline
task will not get a chance to be pulled by another CPU because
load_balance() doesn't take into account tasks from other classes.
Add sum of nr_running in the statistics and use it to detect such
situations.

Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Ben Segall <bsegall@...gle.com>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Juri Lelli <juri.lelli@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Mike Galbraith <efault@....de>
Cc: Morten.Rasmussen@....com
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: hdanton@...a.com
Cc: parth@...ux.ibm.com
Cc: pauld@...hat.com
Cc: quentin.perret@....com
Cc: riel@...riel.com
Cc: srikar@...ux.vnet.ibm.com
Cc: valentin.schneider@....com
Link: https://lkml.kernel.org/r/1571405198-27570-6-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/fair.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 76a2aa8..4e7396c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7694,6 +7694,7 @@ struct sg_lb_stats {
 	unsigned long group_load; /* Total load over the CPUs of the group */
 	unsigned long group_capacity;
 	unsigned long group_util; /* Total utilization of the group */
+	unsigned int sum_nr_running; /* Nr of tasks running in the group */
 	unsigned int sum_h_nr_running; /* Nr of CFS tasks running in the group */
 	unsigned int idle_cpus;
 	unsigned int group_weight;
@@ -7928,7 +7929,7 @@ static inline int sg_imbalanced(struct sched_group *group)
 static inline bool
 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
 {
-	if (sgs->sum_h_nr_running < sgs->group_weight)
+	if (sgs->sum_nr_running < sgs->group_weight)
 		return true;
 
 	if ((sgs->group_capacity * 100) >
@@ -7949,7 +7950,7 @@ group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
 static inline bool
 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
 {
-	if (sgs->sum_h_nr_running <= sgs->group_weight)
+	if (sgs->sum_nr_running <= sgs->group_weight)
 		return false;
 
 	if ((sgs->group_capacity * 100) <
@@ -8053,6 +8054,8 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 		sgs->sum_h_nr_running += rq->cfs.h_nr_running;
 
 		nr_running = rq->nr_running;
+		sgs->sum_nr_running += nr_running;
+
 		if (nr_running > 1)
 			*sg_status |= SG_OVERLOAD;
 
@@ -8410,13 +8413,13 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
 		}
 
 		if (busiest->group_weight == 1 || sds->prefer_sibling) {
-			unsigned int nr_diff = busiest->sum_h_nr_running;
+			unsigned int nr_diff = busiest->sum_nr_running;
 			/*
 			 * When prefer sibling, evenly spread running tasks on
 			 * groups.
 			 */
 			env->migration_type = migrate_task;
-			lsub_positive(&nr_diff, local->sum_h_nr_running);
+			lsub_positive(&nr_diff, local->sum_nr_running);
 			env->imbalance = nr_diff >> 1;
 			return;
 		}
@@ -8580,7 +8583,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
 
 	/* Try to move all excess tasks to child's sibling domain */
 	if (sds.prefer_sibling && local->group_type == group_has_spare &&
-	    busiest->sum_h_nr_running > local->sum_h_nr_running + 1)
+	    busiest->sum_nr_running > local->sum_nr_running + 1)
 		goto force_balance;
 
 	if (busiest->group_type != group_overloaded &&