sched/fair: Simplify the continue_balancing logic in sched_balance_newidle()

newidle(CPU_NEWLY_IDLE) balancing doesn't stop the load-balancing if the
continue_balancing flag is reset, but the other two balancing (IDLE, BUSY)
cases do that.

newidle balance stops the load balancing if rq has a task or there
is wakeup pending. The same checks are present in should_we_balance for
newidle. Hence use the return value and simplify continue_balancing
mechanism for newidle. Update the comment surrounding it as well.

No change in functionality intended.

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20240325153926.274284-1-sshegde@linux.ibm.com

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 24a7530a7d3f60ba468a4de7cec92bbc843aa91e..1856e58595c3d9b09242e94a2151e56978311042 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12358,6 +12358,7 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
 {
        unsigned long next_balance = jiffies + HZ;
        int this_cpu = this_rq->cpu;
+       int continue_balancing = 1;
        u64 t0, t1, curr_cost = 0;
        struct sched_domain *sd;
        int pulled_task = 0;
@@ -12372,8 +12373,9 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
                return 0;
 
        /*
-        * We must set idle_stamp _before_ calling idle_balance(), such that we
-        * measure the duration of idle_balance() as idle time.
+        * We must set idle_stamp _before_ calling sched_balance_rq()
+        * for CPU_NEWLY_IDLE, such that we measure the this duration
+        * as idle time.
         */
        this_rq->idle_stamp = rq_clock(this_rq);
 
@@ -12412,7 +12414,6 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
 
        rcu_read_lock();
        for_each_domain(this_cpu, sd) {
-               int continue_balancing = 1;
                u64 domain_cost;
 
                update_next_balance(sd, &next_balance);
@@ -12438,8 +12439,7 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
                 * Stop searching for tasks to pull if there are
                 * now runnable tasks on this rq.
                 */
-               if (pulled_task || this_rq->nr_running > 0 ||
-                   this_rq->ttwu_pending)
+               if (pulled_task || !continue_balancing)
                        break;
        }
        rcu_read_unlock();