[RFC 1/4] sched/core: Introduce per_cpu counter to track latency sensitive tasks

Parth Shah
2020-05-07T13:37:51Z

The "nr_lat_sensitive" per_cpu variable provides hints on the possible
number of latency-sensitive tasks occupying the CPU. This hints further
helps in inhibiting the CPUIDLE governor from calling deeper IDLE states
(next patches includes this).

Signed-off-by: Parth Shah <parth@linux.ibm.com>
---
kernel/sched/core.c | 2 ++
kernel/sched/sched.h | 2 ++
2 files changed, 4 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2576fd8cacf9..2d8b76f41d61 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6606,6 +6606,7 @@ static struct kmem_cache *task_group_cache __read_mostly;

DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
+DEFINE_PER_CPU(int, nr_lat_sensitive);

void __init sched_init(void)
{
@@ -6737,6 +6738,7 @@ void __init sched_init(void)
#endif /* CONFIG_SMP */
hrtick_rq_init(rq);
atomic_set(&rq->nr_iowait, 0);
+ per_cpu(nr_lat_sensitive, i) = 0;
}

set_load_weight(&init_task, false);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index b2c86dfe913e..5c41020c530e 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1439,6 +1439,8 @@ DECLARE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared);
DECLARE_PER_CPU(struct sched_domain __rcu *, sd_numa);
DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing);
DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity);
+DECLARE_PER_CPU(int, nr_lat_sensitive);
+
extern struct static_key_false sched_asym_cpucapacity;

struct sched_group_capacity {
--
2.17.2