linux-kernel - Re: [PATCH linux-next v3 4/4] sched/psi: Delete the function parameter update_total of update

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Date:   Thu, 19 Oct 2023 09:09:01 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     yang.yang29@....com.cn
Cc:     mingo@...nel.org, peterz@...radead.org, hannes@...xchg.org,
        mingo@...hat.com, linux-kernel@...r.kernel.org,
        juri.lelli@...hat.com
Subject: Re: [PATCH linux-next v3 4/4] sched/psi: Delete the function
 parameter update_total of update_triggers()

On Tue, Oct 10, 2023 at 1:45 AM <yang.yang29@....com.cn> wrote:
>
> From: Yang Yang <yang.yang29@....com.cn>
>
> The parameter update_total in update_triggers() is useless after patch
> "sched/psi: Avoid update triggers and rtpoll_total when it is unnecessary".
> If changed_states & group->rtpoll_states is true, new_stall in
> update_triggers() will be true, then update_total should also
> be true. We have no need for update_total to help judgment
> whether to update rtpoll_total, so delete it.
> This makes the code cleaner & simpler.
>
> Signed-off-by: Yang Yang <yang.yang29@....com.cn>

Acked-by: Suren Baghdasaryan <surenb@...gle.com>

> ---
>  kernel/sched/psi.c | 17 +++--------------
>  1 file changed, 3 insertions(+), 14 deletions(-)
>
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index 79f8db0c6150..44a78774ae87 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -434,14 +434,13 @@ static u64 window_update(struct psi_window *win, u64 now, u64 value)
>         return growth;
>  }
>
> -static void update_triggers(struct psi_group *group, u64 now, bool *update_total,
> +static void update_triggers(struct psi_group *group, u64 now,
>                                                    enum psi_aggregators aggregator)
>  {
>         struct psi_trigger *t;
>         u64 *total = group->total[aggregator];
>         struct list_head *triggers;
>         u64 *aggregator_total;
> -       *update_total = false;
>
>         if (aggregator == PSI_AVGS) {
>                 triggers = &group->avg_triggers;
> @@ -471,14 +470,6 @@ static void update_triggers(struct psi_group *group, u64 now, bool *update_total
>                  * events without dropping any).
>                  */
>                 if (new_stall) {
> -                       /*
> -                        * Multiple triggers might be looking at the same state,
> -                        * remember to update group->polling_total[] once we've
> -                        * been through all of them. Also remember to extend the
> -                        * polling time if we see new stall activity.
> -                        */
> -                       *update_total = true;
> -
>                         /* Calculate growth since last update */
>                         growth = window_update(&t->win, now, total[t->state]);
>                         if (!t->pending_event) {
> @@ -563,7 +554,6 @@ static void psi_avgs_work(struct work_struct *work)
>         struct delayed_work *dwork;
>         struct psi_group *group;
>         u32 changed_states;
> -       bool update_total;
>         u64 now;
>
>         dwork = to_delayed_work(work);
> @@ -582,7 +572,7 @@ static void psi_avgs_work(struct work_struct *work)
>          * go - see calc_avgs() and missed_periods.
>          */
>         if (now >= group->avg_next_update) {
> -               update_triggers(group, now, &update_total, PSI_AVGS);
> +               update_triggers(group, now, PSI_AVGS);
>                 group->avg_next_update = update_averages(group, now);
>         }
>
> @@ -638,7 +628,6 @@ 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);
> @@ -705,7 +694,7 @@ static void psi_rtpoll_work(struct psi_group *group)
>
>         if (now >= group->rtpoll_next_update) {
>                 if (changed_states & group->rtpoll_states) {
> -                       update_triggers(group, now, &update_total, PSI_POLL);
> +                       update_triggers(group, now, PSI_POLL);
>                         memcpy(group->rtpoll_total, group->total[PSI_POLL],
>                                    sizeof(group->rtpoll_total));
>                 }
> --
> 2.25.1