[tip:sched/core] sched/fair: Expose newidle_balance()

[tip-bot for Peter Zijlstra]

Commit-ID:  5ba553eff0c3a7c099b1e29a740277a82c0c3314
Gitweb:     https://git.kernel.org/tip/5ba553eff0c3a7c099b1e29a740277a82c0c3314
Author:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Wed, 29 May 2019 20:36:42 +0000
Committer:  Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitDate: Thu, 8 Aug 2019 09:09:31 +0200

sched/fair: Expose newidle_balance()

For pick_next_task_fair() it is the newidle balance that requires
dropping the rq->lock; provided we do put_prev_task() early, we can
also detect the condition for doing newidle early.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Aaron Lu <aaron.lwe@xxxxxxxxx>
Cc: Valentin Schneider <valentin.schneider@xxxxxxx>
Cc: mingo@xxxxxxxxxx
Cc: Phil Auld <pauld@xxxxxxxxxx>
Cc: Julien Desfossez <jdesfossez@xxxxxxxxxxxxxxxx>
Cc: Nishanth Aravamudan <naravamudan@xxxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/9e3eb1859b946f03d7e500453a885725b68957ba.1559129225.git.vpillai@xxxxxxxxxxxxxxxx
---
 kernel/sched/fair.c  | 18 ++++++++----------
 kernel/sched/sched.h |  4 ++++
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8ce1b8893947..e7c27eda9f24 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3690,8 +3690,6 @@ static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
 	return cfs_rq->avg.load_avg;
 }
 
-static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
-
 static inline unsigned long task_util(struct task_struct *p)
 {
 	return READ_ONCE(p->se.avg.util_avg);
@@ -6878,11 +6876,10 @@ done: __maybe_unused;
 	return p;
 
 idle:
-	update_misfit_status(NULL, rq);
-	new_tasks = idle_balance(rq, rf);
+	new_tasks = newidle_balance(rq, rf);
 
 	/*
-	 * Because idle_balance() releases (and re-acquires) rq->lock, it is
+	 * Because newidle_balance() releases (and re-acquires) rq->lock, it is
 	 * possible for any higher priority task to appear. In that case we
 	 * must re-start the pick_next_entity() loop.
 	 */
@@ -9045,10 +9042,10 @@ out_one_pinned:
 	ld_moved = 0;
 
 	/*
-	 * idle_balance() disregards balance intervals, so we could repeatedly
-	 * reach this code, which would lead to balance_interval skyrocketting
-	 * in a short amount of time. Skip the balance_interval increase logic
-	 * to avoid that.
+	 * newidle_balance() disregards balance intervals, so we could
+	 * repeatedly reach this code, which would lead to balance_interval
+	 * skyrocketting in a short amount of time. Skip the balance_interval
+	 * increase logic to avoid that.
 	 */
 	if (env.idle == CPU_NEWLY_IDLE)
 		goto out;
@@ -9758,7 +9755,7 @@ static inline void nohz_newidle_balance(struct rq *this_rq) { }
  * idle_balance is called by schedule() if this_cpu is about to become
  * idle. Attempts to pull tasks from other CPUs.
  */
-static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
+int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
 {
 	unsigned long next_balance = jiffies + HZ;
 	int this_cpu = this_rq->cpu;
@@ -9766,6 +9763,7 @@ static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
 	int pulled_task = 0;
 	u64 curr_cost = 0;
 
+	update_misfit_status(NULL, this_rq);
 	/*
 	 * We must set idle_stamp _before_ calling idle_balance(), such that we
 	 * measure the duration of idle_balance() as idle time.
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index f3c50445bf22..304d98e712bf 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1445,10 +1445,14 @@ static inline void unregister_sched_domain_sysctl(void)
 }
 #endif
 
+extern int newidle_balance(struct rq *this_rq, struct rq_flags *rf);
+
 #else
 
 static inline void sched_ttwu_pending(void) { }
 
+static inline int newidle_balance(struct rq *this_rq, struct rq_flags *rf) { return 0; }
+
 #endif /* CONFIG_SMP */
 
 #include "stats.h"