Re: [PATCH v6 3/4] sched/psi: extract update_triggers side effect

[Suren Baghdasaryan]

On Thu, Mar 30, 2023 at 3:54 AM Domenico Cerasuolo
<cerasuolodomenico@xxxxxxxxx> wrote:
>
> This change moves update_total flag out of update_triggers function,
> currently called only in psi_poll_work.
> In the next patch, update_triggers will be called also in psi_avgs_work,
> but the total update information is specific to psi_poll_work.
> Returning update_total value to the caller let us avoid differentiating
> the implementation of update_triggers for different aggregators.
>
> Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx>
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>

Acked-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>

> ---
>  kernel/sched/psi.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index a3d0b5cf797a..f3df6a8ff493 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -430,11 +430,11 @@ static u64 window_update(struct psi_window *win, u64 now, u64 value)
>         return growth;
>  }
>
> -static u64 update_triggers(struct psi_group *group, u64 now)
> +static u64 update_triggers(struct psi_group *group, u64 now, bool *update_total)
>  {
>         struct psi_trigger *t;
> -       bool update_total = false;
>         u64 *total = group->total[PSI_POLL];
> +       *update_total = false;
>
>         /*
>          * On subsequent updates, calculate growth deltas and let
> @@ -462,7 +462,7 @@ static u64 update_triggers(struct psi_group *group, u64 now)
>                          * been through all of them. Also remember to extend the
>                          * polling time if we see new stall activity.
>                          */
> -                       update_total = true;
> +                       *update_total = true;
>
>                         /* Calculate growth since last update */
>                         growth = window_update(&t->win, now, total[t->state]);
> @@ -485,10 +485,6 @@ static u64 update_triggers(struct psi_group *group, u64 now)
>                 t->pending_event = false;
>         }
>
> -       if (update_total)
> -               memcpy(group->rtpoll_total, total,
> -                               sizeof(group->rtpoll_total));
> -
>         return now + group->rtpoll_min_period;
>  }
>
> @@ -622,6 +618,7 @@ static void psi_rtpoll_work(struct psi_group *group)
>  {
>         bool force_reschedule = false;
>         u32 changed_states;
> +       bool update_total;
>         u64 now;
>
>         mutex_lock(&group->rtpoll_trigger_lock);
> @@ -686,8 +683,12 @@ static void psi_rtpoll_work(struct psi_group *group)
>                 goto out;
>         }
>
> -       if (now >= group->rtpoll_next_update)
> -               group->rtpoll_next_update = update_triggers(group, now);
> +       if (now >= group->rtpoll_next_update) {
> +               group->rtpoll_next_update = update_triggers(group, now, &update_total);
> +               if (update_total)
> +                       memcpy(group->rtpoll_total, group->total[PSI_POLL],
> +                                  sizeof(group->rtpoll_total));
> +       }
>
>         psi_schedule_rtpoll_work(group,
>                 nsecs_to_jiffies(group->rtpoll_next_update - now) + 1,
> --
> 2.34.1
>