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Subject[tip: sched/core] sched/fair: Reduce busy load balance interval
The following commit has been merged into the sched/core branch of tip:

Commit-ID: 6e7499135db724539ca887b3aa64122502875c71
Gitweb: https://git.kernel.org/tip/6e7499135db724539ca887b3aa64122502875c71
Author: Vincent Guittot <vincent.guittot@linaro.org>
AuthorDate: Mon, 21 Sep 2020 09:24:24 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 25 Sep 2020 14:23:26 +02:00

sched/fair: Reduce busy load balance interval

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
---
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 41df628..a3a2417 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1348,7 +1348,7 @@ 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,
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