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charset="utf-8" In current newidle balance, the rq->idle_stamp may set to a non-zero value if it cannot pull any task. In the wakeup, it will detect the rq->idle_stamp, and updates the rq->avg_idle, then ends the CPU idle status by setting rq->idle_stamp to zero. Besides the wakeup, current code does not end the CPU idle status when a task is moved to the idle CPU, such as fork/clone, execve, or other cases. In order to fix this issue, we want to add a hook(update_rq_avg_idle()) in the enqueue_task(). With this hook, if a task is moved to the idle CPU, it will update the rq->avg_idle. Unfortunately, this hook is also called in the newidle balance: sched_balance_newidle() --> sched_balance_rq() --> ... --> enqueue_task() If we still set rq->idle_stamp at the beginning of sched_balance_newidle(), the rq->avg_idle will not be updated correctly. In order to make it work correctly, save the idle_stamp at the beginning of sched_balance_newidle(). If newidle balance cannot pull any task, set the saved value for rq->idle_stamp. With this method, the newidle balance still work correctly, and the hook in enqueue_task() also works correctly. Signed-off-by: Huang Shijie --- kernel/sched/fair.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1855975b8248..c3b4895f8e50 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -12865,6 +12865,7 @@ static int sched_balance_newidle(struct rq *this_rq= , struct rq_flags *rf) u64 t0, t1, curr_cost =3D 0; struct sched_domain *sd; int pulled_task =3D 0; + u64 idle_stamp; =20 update_misfit_status(NULL, this_rq); =20 @@ -12880,7 +12881,7 @@ static int sched_balance_newidle(struct rq *this_rq= , struct rq_flags *rf) * for CPU_NEWLY_IDLE, such that we measure the this duration * as idle time. */ - this_rq->idle_stamp =3D rq_clock(this_rq); + idle_stamp =3D rq_clock(this_rq); =20 /* * Do not pull tasks towards !active CPUs... @@ -12992,10 +12993,13 @@ static int sched_balance_newidle(struct rq *this_= rq, struct rq_flags *rf) if (time_after(this_rq->next_balance, next_balance)) this_rq->next_balance =3D next_balance; =20 - if (pulled_task) + if (pulled_task) { this_rq->idle_stamp =3D 0; - else + } else { + /* Set it here on purpose. */ + this_rq->idle_stamp =3D idle_stamp; nohz_newidle_balance(this_rq); + } =20 rq_repin_lock(this_rq, rf); =20 --=20 2.40.1