[RFC PATCH 4/9] sched: SIS_CORE to disable idle core search

From: subhra mazumdar
Date: Fri Aug 30 2019 - 13:56:01 EST


Use SIS_CORE to disable idle core search. For some workloads
select_idle_core becomes a scalability bottleneck, removing it improves
throughput. Also there are workloads where disabling it can hurt latency,
so need to have an option.

Signed-off-by: subhra mazumdar <subhra.mazumdar@xxxxxxxxxx>
---
kernel/sched/fair.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c31082d..23ec9c6 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6268,9 +6268,11 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
if (!sd)
return target;

- i = select_idle_core(p, sd, target);
- if ((unsigned)i < nr_cpumask_bits)
- return i;
+ if (sched_feat(SIS_CORE)) {
+ i = select_idle_core(p, sd, target);
+ if ((unsigned)i < nr_cpumask_bits)
+ return i;
+ }

i = select_idle_cpu(p, sd, target);
if ((unsigned)i < nr_cpumask_bits)
--
2.9.3