linux-kernel - [RFC 28/60] cosched: Add is_sd_se() to distinguish SD-SEs from TG-SEs

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Message-Id: <20180907214047.26914-29-jschoenh@amazon.de>
Date:   Fri,  7 Sep 2018 23:40:15 +0200
From:   Jan H. Schönherr <jschoenh@...zon.de>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Jan H. Schönherr <jschoenh@...zon.de>,
        linux-kernel@...r.kernel.org
Subject: [RFC 28/60] cosched: Add is_sd_se() to distinguish SD-SEs from TG-SEs

Add a function is_sd_se() to easily distinguish SD-SEs from a TG-SEs.

Internally, we distinguish tasks, SD-SEs, and TG-SEs based on the my_q
field. For tasks it is empty, for TG-SEs it is a pointer, and for
SD-SEs it is a magic value.

Also modify propagate_entity_load_avg() to not page fault on SD-SEs.

Signed-off-by: Jan H. Schönherr <jschoenh@...zon.de>
---
 kernel/sched/fair.c  | 12 +++++-------
 kernel/sched/sched.h | 14 ++++++++++++++
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 18b1d81951f1..9cbdd027d449 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -279,6 +279,8 @@ static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
 /* runqueue "owned" by this group */
 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
 {
+	if (grp->my_q == INDIRECT_GROUP)
+		return NULL;
 	return grp->my_q;
 }
 
@@ -3240,13 +3242,9 @@ static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum
 /* Update task and its cfs_rq load average */
 static inline int propagate_entity_load_avg(struct sched_entity *se)
 {
-	struct cfs_rq *cfs_rq, *gcfs_rq;
-
-	if (entity_is_task(se))
-		return 0;
+	struct cfs_rq *cfs_rq, *gcfs_rq = group_cfs_rq(se);
 
-	gcfs_rq = group_cfs_rq(se);
-	if (!gcfs_rq->propagate)
+	if (!gcfs_rq || !gcfs_rq->propagate)
 		return 0;
 
 	gcfs_rq->propagate = 0;
@@ -9931,7 +9929,7 @@ void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
 	/* se is NULL for root_task_group */
 	if (se) {
 		set_entity_cfs(se, parent);
-		se->my_q = cfs_rq;
+		se->my_q = cfs_rq ?: INDIRECT_GROUP;
 
 		/* guarantee group entities always have weight */
 		update_load_set(&se->load, NICE_0_LOAD);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 456b266b8a2c..5e2d231b1dbf 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1146,6 +1146,13 @@ static inline struct rq *parent_rq(struct rq *rq)
 		return NULL;
 	return container_of(rq->sdrq_data.parent, struct rq, sdrq_data);
 }
+
+#define INDIRECT_GROUP		ERR_PTR(-EREMOTE)
+
+static inline bool is_sd_se(struct sched_entity *se)
+{
+	return se->my_q == INDIRECT_GROUP;
+}
 #else /* !CONFIG_COSCHEDULING */
 static inline int node_of(struct rq *rq)
 {
@@ -1161,6 +1168,13 @@ static inline struct rq *parent_rq(struct rq *rq)
 {
 	return NULL;
 }
+
+#define INDIRECT_GROUP		NULL
+
+static inline bool is_sd_se(struct sched_entity *se)
+{
+	return false;
+}
 #endif /* !CONFIG_COSCHEDULING */
 
 #ifdef CONFIG_COSCHEDULING
-- 
2.9.3.1.gcba166c.dirty