[PATCH 2/4] sched/fair: Introduce idle enter/exit balance callbacks

From: Jiri Olsa
Date: Mon Jun 20 2016 - 08:23:47 EST


Introducing idle enter/exit balance callbacks to keep
balance.idle_cpus_mask cpumask of current idle cpus
in system.

It's used only when REBALANCE_AFFINITY feature is
switched on. The code functionality of this feature
is introduced in following patch.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
kernel/sched/fair.c | 32 ++++++++++++++++++++++++++++++++
kernel/sched/idle.c | 2 ++
kernel/sched/sched.h | 3 +++
3 files changed, 37 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f19c9435c64d..78c4127f2f3a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7802,6 +7802,37 @@ static inline int on_null_domain(struct rq *rq)
return unlikely(!rcu_dereference_sched(rq->sd));
}

+static struct {
+ cpumask_var_t idle_cpus_mask;
+ atomic_t nr_cpus;
+} balance ____cacheline_aligned;
+
+void sched_idle_enter(int cpu)
+{
+ if (!sched_feat(REBALANCE_AFFINITY))
+ return;
+
+ if (!cpu_active(cpu))
+ return;
+
+ if (on_null_domain(cpu_rq(cpu)))
+ return;
+
+ cpumask_set_cpu(cpu, balance.idle_cpus_mask);
+ atomic_inc(&balance.nr_cpus);
+}
+
+void sched_idle_exit(int cpu)
+{
+ if (!sched_feat(REBALANCE_AFFINITY))
+ return;
+
+ if (likely(cpumask_test_cpu(cpu, balance.idle_cpus_mask))) {
+ cpumask_clear_cpu(cpu, balance.idle_cpus_mask);
+ atomic_dec(&balance.nr_cpus);
+ }
+}
+
#ifdef CONFIG_NO_HZ_COMMON
/*
* idle load balancing details
@@ -8731,6 +8762,7 @@ __init void init_sched_fair_class(void)
nohz.next_balance = jiffies;
zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
+ zalloc_cpumask_var(&balance.idle_cpus_mask, GFP_NOWAIT);
#endif /* SMP */

}
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index db4ff7c100b9..0cc0109eacd3 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -216,6 +216,7 @@ static void cpu_idle_loop(void)
__current_set_polling();
quiet_vmstat();
tick_nohz_idle_enter();
+ sched_idle_enter(cpu);

while (!need_resched()) {
check_pgt_cache();
@@ -256,6 +257,7 @@ static void cpu_idle_loop(void)
*/
preempt_set_need_resched();
tick_nohz_idle_exit();
+ sched_idle_exit(cpu);
__current_clr_polling();

/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 72f1f3087b04..d1a6224cd140 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1692,6 +1692,9 @@ extern void init_dl_rq(struct dl_rq *dl_rq);
extern void cfs_bandwidth_usage_inc(void);
extern void cfs_bandwidth_usage_dec(void);

+void sched_idle_enter(int cpu);
+void sched_idle_exit(int cpu);
+
#ifdef CONFIG_NO_HZ_COMMON
enum rq_nohz_flag_bits {
NOHZ_TICK_STOPPED,
--
2.4.11