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Subject[RFC][PATCH 06/16] sched/fair: Export 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@infradead.org>
---
kernel/sched/fair.c | 18 ++++++++----------
kernel/sched/sched.h | 4 ++++
2 files changed, 12 insertions(+), 10 deletions(-)

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3610,8 +3610,6 @@ static inline unsigned long cfs_rq_load_
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);
@@ -7057,11 +7055,10 @@ 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.
*/
@@ -9243,10 +9240,10 @@ static int load_balance(int this_cpu, st
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;
@@ -9923,7 +9920,7 @@ static inline void nohz_newidle_balance(
* 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;
@@ -9931,6 +9928,7 @@ static int idle_balance(struct rq *this_
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.
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1414,10 +1414,14 @@ static inline void unregister_sched_doma
}
#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"

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