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Subject[PATCH 05/10] sched/fair: Hoist idle_stamp up from idle_balance
Date
Move the update of idle_stamp from idle_balance to the call site in
pick_next_task_fair, to prepare for a future patch that adds work to
pick_next_task_fair which must be included in the idle_stamp interval.
No functional change.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
kernel/sched/fair.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c623338..9f31045 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3724,6 +3724,8 @@ static inline bool within_margin(int value, int margin)
WRITE_ONCE(p->se.avg.util_est, ue);
}

+#define IF_SMP(statement) statement
+
static void overload_clear(struct rq *rq)
{
struct sparsemask *overload_cpus;
@@ -3769,6 +3771,8 @@ static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
return 0;
}

+#define IF_SMP(statement) /* empty */
+
static inline void overload_clear(struct rq *rq) {}
static inline void overload_set(struct rq *rq) {}

@@ -6740,8 +6744,19 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
return p;

idle:
+ /*
+ * We must set idle_stamp _before_ calling idle_balance(), such that we
+ * measure the duration of idle_balance() as idle time.
+ */
+ IF_SMP(rq->idle_stamp = rq_clock(rq);)
+
new_tasks = idle_balance(rq, rf);

+ if (new_tasks)
+ IF_SMP(rq->idle_stamp = 0;)
+
+ schedstat_end_time(rq->find_time, time);
+
/*
* Because idle_balance() releases (and re-acquires) rq->lock, it is
* possible for any higher priority task to appear. In that case we
@@ -9504,12 +9519,6 @@ static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
u64 curr_cost = 0;

/*
- * We must set idle_stamp _before_ calling idle_balance(), such that we
- * measure the duration of idle_balance() as idle time.
- */
- this_rq->idle_stamp = rq_clock(this_rq);
-
- /*
* Do not pull tasks towards !active CPUs...
*/
if (!cpu_active(this_cpu))
@@ -9600,9 +9609,6 @@ static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
if (this_rq->nr_running != this_rq->cfs.h_nr_running)
pulled_task = -1;

- if (pulled_task)
- this_rq->idle_stamp = 0;
-
rq_repin_lock(this_rq, rf);

return pulled_task;
--
1.8.3.1
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