[PATCH tip 1/2] sched/fair: Push down check for high priority class task into idle_balance()

From: Kirill Tkhai
Date: Thu Mar 06 2014 - 04:33:18 EST


We close idle_exit_fair() bracket in case of we've pulled something or we've received
task of high priority class.

Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/fair.c | 15 ++++++++++-----
kernel/sched/idle_task.c | 1 -
2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d8482e1..b956e70 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4787,17 +4787,16 @@ simple:
return p;

idle:
+ new_tasks = idle_balance(rq);
/*
* Because idle_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.
*/
- new_tasks = idle_balance(rq);
-
- if (rq->nr_running != rq->cfs.h_nr_running)
+ if (new_tasks < 0)
return RETRY_TASK;

- if (new_tasks)
+ if (new_tasks > 0)
goto again;

return NULL;
@@ -6728,8 +6727,14 @@ static int idle_balance(struct rq *this_rq)
this_rq->max_idle_balance_cost = curr_cost;

out:
- if (pulled_task)
+ /* Is there a task of a high priority class? */
+ if (this_rq->nr_running != this_rq->cfs.h_nr_running)
+ pulled_task = -1;
+
+ if (pulled_task) {
+ idle_exit_fair(this_rq);
this_rq->idle_stamp = 0;
+ }

return pulled_task;
}
diff --git a/kernel/sched/idle_task.c b/kernel/sched/idle_task.c
index 1f37258..879f2b7 100644
--- a/kernel/sched/idle_task.c
+++ b/kernel/sched/idle_task.c
@@ -29,7 +29,6 @@ pick_next_task_idle(struct rq *rq, struct task_struct *prev)
put_prev_task(rq, prev);

schedstat_inc(rq, sched_goidle);
- idle_enter_fair(rq);
return rq->idle;
}




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