[RFC PATCH 4/4] sched/core: Do numa balance in cfs_migration

[Yafang Shao]

Similar to active load balance, the numa balance work is also applied to
cfs tasks only and it should't preempt other FIFO tasks. We'd better assign
cfs_migration to the numa balance as well.

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Cc: Valentin Schneider <valentin.schneider@xxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
---
 kernel/sched/core.c  |  2 +-
 kernel/sched/fair.c  | 13 +++++++++++++
 kernel/sched/sched.h |  2 ++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9cb81ef8acc8..4a37b06715f4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8724,7 +8724,7 @@ int migrate_task_to(struct task_struct *p, int target_cpu)
 	/* TODO: This is not properly updating schedstats */
 
 	trace_sched_move_numa(p, curr_cpu, target_cpu);
-	return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
+	return wakeup_cfs_migrater(curr_cpu, migration_cpu_stop, &arg);
 }
 
 /*
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 932f63baeb82..b7a155e05c98 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11960,6 +11960,19 @@ static void wakeup_cfs_migrater_nowait(unsigned int cpu, cpu_stop_fn_t fn, void
 	cfs_migration_queue_work(cpu, work_buf);
 }
 
+bool wakeup_cfs_migrater(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
+{
+	struct cpu_stop_done done;
+	struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done, .caller = _RET_IP_ };
+
+	cpu_stop_init_done(&done, 1);
+	cfs_migration_queue_work(cpu, &work);
+	cond_resched();
+	wait_for_completion(&done.completion);
+
+	return done.ret;
+}
+
 static int cfs_migration_should_run(unsigned int cpu)
 {
 	struct cfs_migrater *migrater = &per_cpu(cfs_migrater, cpu);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index a00fc7057d97..7b242c18a6d8 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3055,6 +3055,8 @@ static inline bool is_per_cpu_kthread(struct task_struct *p)
 
 	return true;
 }
+
+bool wakeup_cfs_migrater(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
 #endif
 
 extern void swake_up_all_locked(struct swait_queue_head *q);
-- 
2.17.1