[PATCH v2 3/3] sched/fair: Rename sgc->imbalance to sgc->pinned_imb

[Jemmy Wong]

sgc->imbalance does not describe a load skew either. It is set only
when a child domain failed to balance because some tasks were pinned by
cpus_ptr, and the parent then classifies the group as group_pinned_imb
so that it can force a migration.

The unqualified name is easily confused with env->imbalance, the amount
of load still to move, and with imbalance_pct. And after the previous
rename, sg_imbalanced() returns group_pinned_imb, so the helper and the
group type no longer agree.

Rename the field to pinned_imb and its reader to sg_pinned_imb().

No functional change.

Signed-off-by: Jemmy Wong <jemmywong512@xxxxxxxxx>
---
 kernel/sched/fair.c  | 24 ++++++++++++------------
 kernel/sched/sched.h |  6 +++++-
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 49de871ee7ab..0f773e1af9f5 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11832,7 +11832,7 @@ static inline bool check_misfit_status(struct rq *rq)
 }
 
 /*
- * Group imbalance indicates (and tries to solve) the problem where balancing
+ * sgc->pinned_imb indicates (and tries to solve) the problem where balancing
  * groups is inadequate due to ->cpus_ptr constraints.
  *
  * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
@@ -11860,9 +11860,9 @@ static inline bool check_misfit_status(struct rq *rq)
  * subtle and fragile situation.
  */
 
-static inline int sg_imbalanced(struct sched_group *group)
+static inline int sg_pinned_imb(struct sched_group *group)
 {
-	return group->sgc->imbalance;
+	return group->sgc->pinned_imb;
 }
 
 /*
@@ -11937,7 +11937,7 @@ group_type group_classify(unsigned int imbalance_pct,
 	if (sgs->group_llc_balance)
 		return group_llc_balance;
 
-	if (sg_imbalanced(group))
+	if (sg_pinned_imb(group))
 		return group_pinned_imb;
 
 	if (sgs->group_asym_packing)
@@ -13870,10 +13870,10 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq,
 		 * We failed to reach balance because of affinity.
 		 */
 		if (sd_parent) {
-			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
+			int *pinned_imb = &sd_parent->groups->sgc->pinned_imb;
 
 			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
-				*group_imbalance = 1;
+				*pinned_imb = 1;
 		}
 
 		/* All tasks on this runqueue were pinned by CPU affinity */
@@ -13973,21 +13973,21 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq,
 out_balanced:
 	/*
 	 * We reach balance although we may have faced some affinity
-	 * constraints. Clear the imbalance flag only if other tasks got
+	 * constraints. Clear the pinned flag only if other tasks got
 	 * a chance to move and fix the imbalance.
 	 */
 	if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
-		int *group_imbalance = &sd_parent->groups->sgc->imbalance;
+		int *pinned_imb = &sd_parent->groups->sgc->pinned_imb;
 
-		if (*group_imbalance)
-			*group_imbalance = 0;
+		if (*pinned_imb)
+			*pinned_imb = 0;
 	}
 
 out_all_pinned:
 	/*
 	 * We reach balance because all tasks are pinned at this level so
-	 * we can't migrate them. Let the imbalance flag set so parent level
-	 * can try to migrate them.
+	 * we can't migrate them. Let the pinned flag stay set so the parent
+	 * level can try to migrate them.
 	 */
 	schedstat_inc(sd->lb_balanced[idle]);
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e656c7059bf8..14ce0f6e6027 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2257,7 +2257,11 @@ struct sched_group_capacity {
 	unsigned long		min_capacity;		/* Min per-CPU capacity in group */
 	unsigned long		max_capacity;		/* Max per-CPU capacity in group */
 	unsigned long		next_update;
-	int			imbalance;		/* XXX unrelated to capacity but shared group state */
+	/*
+	 * Set when a child domain cannot balance pinned tasks.
+	 * XXX unrelated to capacity, but it is shared group state.
+	 */
+	int			pinned_imb;
 
 	int			id;
 
-- 
2.54.0 (Apple Git-157)