From db040c96a9f0dd859c334dbd966432d68b5aeed2 Mon Sep 17 00:00:00 2001
From: Vincent Guittot <vincent.guittot@linaro.org>
Date: Mon, 21 Sep 2020 09:24:24 +0200
Subject: [PATCH] sched/fair: Reduce busy load balance interval

References: bnc#1155798 (CPU scheduler functional and performance backports)
Git-commit: 6e7499135db724539ca887b3aa64122502875c71
Patch-mainline: v5.10-rc1

The busy_factor, which increases load balance interval when a cpu is busy,
is set to 32 by default. This value generates some huge LB interval on
large system like the THX2 made of 2 node x 28 cores x 4 threads.
For such system, the interval increases from 112ms to 3584ms at MC level.
And from 228ms to 7168ms at NUMA level.

Even on smaller system, a lower busy factor has shown improvement on the
fair distribution of the running time so let reduce it for all.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Link: https://lkml.kernel.org/r/20200921072424.14813-5-vincent.guittot@linaro.org
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 kernel/sched/topology.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 9f54e0915b4c..7cfc22ca94f2 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1346,7 +1346,7 @@ sd_init(struct sched_domain_topology_level *tl,
 	*sd = (struct sched_domain){
 		.min_interval		= sd_weight,
 		.max_interval		= 2*sd_weight,
-		.busy_factor		= 32,
+		.busy_factor		= 16,
 		.imbalance_pct		= 117,
 
 		.cache_nice_tries	= 0,