[2/4] sched: Avoid unnecessary calculation of load imbalance at clone time
diff mbox series

Message ID 20201119083027.31335-3-mgorman@techsingularity.net
State New, archived
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Series
  • Revisit NUMA imbalance tolerance and fork balancing
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Commit Message

Mel Gorman Nov. 19, 2020, 8:30 a.m. UTC
In find_idlest_group(), the load imbalance is only relevant when the group
is either overloaded or fully busy but it is calculated unconditionally.
This patch moves the imbalance calculation to the context it is required.
Technically, it is a micro-optimisation but really the benefit is avoiding
confusing one type of imbalance with another depending on the group_type
in the next patch.

No functional change.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 kernel/sched/fair.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Patch
diff mbox series

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 5fbed29e4001..9aded12aaa90 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8777,9 +8777,6 @@  find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
 			.group_type = group_overloaded,
 	};
 
-	imbalance = scale_load_down(NICE_0_LOAD) *
-				(sd->imbalance_pct-100) / 100;
-
 	do {
 		int local_group;
 
@@ -8833,6 +8830,11 @@  find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
 	switch (local_sgs.group_type) {
 	case group_overloaded:
 	case group_fully_busy:
+
+		/* Calculate allowed imbalance based on load */
+		imbalance = scale_load_down(NICE_0_LOAD) *
+				(sd->imbalance_pct-100) / 100;
+
 		/*
 		 * When comparing groups across NUMA domains, it's possible for
 		 * the local domain to be very lightly loaded relative to the