On Mon, 5 Oct 2020 at 17:09, Peter Zijlstra <[email protected]> wrote:
>
> Since we now migrate tasks away before DYING, we should also move
> bandwidth unthrottle, otherwise we can gain tasks from unthrottle
> after we expect all tasks to be gone already.
>
> Also; it looks like the RT balancers don't respect cpu_active() and
> instead rely on rq->online in part, complete this. This too requires
> we do set_rq_offline() earlier to match the cpu_active() semantics.
> (The bigger patch is to convert RT to cpu_active() entirely)
>
> Since set_rq_online() is called from sched_cpu_activate(), place
> set_rq_offline() in sched_cpu_deactivate().
>
> Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
> ---
> kernel/sched/core.c | 14 ++++++++++----
> kernel/sched/deadline.c | 5 +----
> kernel/sched/rt.c | 5 +----
> 3 files changed, 12 insertions(+), 12 deletions(-)
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6979,6 +6979,8 @@ int sched_cpu_activate(unsigned int cpu)
>
> int sched_cpu_deactivate(unsigned int cpu)
> {
> + struct rq *rq = cpu_rq(cpu);
> + struct rq_flags rf;
> int ret;
>
> set_cpu_active(cpu, false);
> @@ -6993,6 +6995,14 @@ int sched_cpu_deactivate(unsigned int cp
>
> balance_push_set(cpu, true);
>
> + rq_lock_irqsave(rq, &rf);
> + if (rq->rd) {
> + update_rq_clock();
Tried to compile but rq parameter is missing
> + BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
> + set_rq_offline(rq);
> + }
> + rq_unlock_irqrestore(rq, &rf);
> +
> #ifdef CONFIG_SCHED_SMT
> /*
> * When going down, decrement the number of cores with SMT present.
> @@ -7074,10 +7084,6 @@ int sched_cpu_dying(unsigned int cpu)
> sched_tick_stop(cpu);
>
> rq_lock_irqsave(rq, &rf);
> - if (rq->rd) {
> - BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
> - set_rq_offline(rq);
> - }
> BUG_ON(rq->nr_running != 1);
> rq_unlock_irqrestore(rq, &rf);
>
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -543,7 +543,7 @@ static int push_dl_task(struct rq *rq);
>
> static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
> {
> - return dl_task(prev);
> + return rq->online && dl_task(prev);
> }
>
> static DEFINE_PER_CPU(struct callback_head, dl_push_head);
> @@ -2326,9 +2326,6 @@ static void rq_online_dl(struct rq *rq)
> /* Assumes rq->lock is held */
> static void rq_offline_dl(struct rq *rq)
> {
> - if (rq->dl.overloaded)
> - dl_clear_overload(rq);
> -
> cpudl_clear(&rq->rd->cpudl, rq->cpu);
> cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
> }
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -265,7 +265,7 @@ static void pull_rt_task(struct rq *this
> static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
> {
> /* Try to pull RT tasks here if we lower this rq's prio */
> - return rq->rt.highest_prio.curr > prev->prio;
> + return rq->online && rq->rt.highest_prio.curr > prev->prio;
> }
>
> static inline int rt_overloaded(struct rq *rq)
> @@ -2245,9 +2245,6 @@ static void rq_online_rt(struct rq *rq)
> /* Assumes rq->lock is held */
> static void rq_offline_rt(struct rq *rq)
> {
> - if (rq->rt.overloaded)
> - rt_clear_overload(rq);
> -
> __disable_runtime(rq);
>
> cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
>
>
