[linux-next] sched/psi: avoid unnecessary resetting min update period when destroy trigger

  From: Yang Yang <yang.yang19@zte.com.cn>

Psi_group's poll_min_period is determined by the min window size of
psi_trigger when creating new triggers. While destroying a psi_trigger,
there is no need to reset poll_min_period if the destroying psi_trigger
not had the min windows size, since in this condition poll_min_period
will keep the same as before.

Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
---
 kernel/sched/psi.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)
  

On Mon, Apr 17, 2023 at 1:12 AM <yang.yang29@zte.com.cn> wrote:
>
> From: Yang Yang <yang.yang19@zte.com.cn>
>
> Psi_group's poll_min_period is determined by the min window size of
> psi_trigger when creating new triggers. While destroying a psi_trigger,
> there is no need to reset poll_min_period if the destroying psi_trigger
> not had the min windows size, since in this condition poll_min_period
> will keep the same as before.

Nice optimization.

>
> Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>

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

> ---
>  kernel/sched/psi.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index 02e011cabe91..12869585cf89 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -1359,11 +1359,16 @@ void psi_trigger_destroy(struct psi_trigger *t)
>                 group->nr_triggers[t->state]--;
>                 if (!group->nr_triggers[t->state])
>                         group->poll_states &= ~(1 << t->state);
> -               /* reset min update period for the remaining triggers */
> -               list_for_each_entry(tmp, &group->triggers, node)
> -                       period = min(period, div_u64(tmp->win.size,
> -                                       UPDATES_PER_WINDOW));
> -               group->poll_min_period = period;
> +               /*
> +                * Reset min update period for the remaining triggers iff the destroying
> +                * trigger had the min window size.
> +                */
> +               if (group->poll_min_period == div_u64(t->win.size, UPDATES_PER_WINDOW)) {
> +                       list_for_each_entry(tmp, &group->triggers, node)
> +                               period = min(period, div_u64(tmp->win.size,
> +                                               UPDATES_PER_WINDOW));
> +                       group->poll_min_period = period;
> +               }
>                 /* Destroy poll_task when the last trigger is destroyed */
>                 if (group->poll_states == 0) {
>                         group->polling_until = 0;
> --
> 2.25.1
  

>On Mon, Apr 17, 2023 at 1:12 AM <yang.yang29@zte.com.cn> wrote:
>>
>> From: Yang Yang <yang.yang19@zte.com.cn>
>>
>> Psi_group's poll_min_period is determined by the min window size of
>> psi_trigger when creating new triggers. While destroying a psi_trigger,
>> there is no need to reset poll_min_period if the destroying psi_trigger
>> not had the min windows size, since in this condition poll_min_period
>> will keep the same as before.
>
> Nice optimization.
>
>> Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
> Acked-by: Suren Baghdasaryan <surenb@google.com>

Hi, would you please take a review?
Thanks!
  

>On Mon, Apr 17, 2023 at 1:12 AM <yang.yang29@zte.com.cn> wrote:
>>
>> From: Yang Yang <yang.yang19@zte.com.cn>
>>
>> Psi_group's poll_min_period is determined by the min window size of
>> psi_trigger when creating new triggers. While destroying a psi_trigger,
>> there is no need to reset poll_min_period if the destroying psi_trigger
>> not had the min windows size, since in this condition poll_min_period
>> will keep the same as before.
>
> Nice optimization.
>
>> Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
> Acked-by: Suren Baghdasaryan <surenb@google.com>

Hi, would you please take a review?
Thanks!
  

> On Mon, Apr 17, 2023 at 1:12 AM <yang.yang29@zte.com.cn> wrote:
>>
>> From: Yang Yang <yang.yang19@zte.com.cn>
>>
>> Psi_group's poll_min_period is determined by the min window size of
>> psi_trigger when creating new triggers. While destroying a psi_trigger,
>> there is no need to reset poll_min_period if the destroying psi_trigger
>> not had the min windows size, since in this condition poll_min_period
>> will keep the same as before.
>
> Nice optimization.
>
>>
>> Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
>
> Acked-by: Suren Baghdasaryan <surenb@google.com>

Hi, would you please take a review?
Thanks!
  

On Tue, Apr 25, 2023 at 8:32 PM Yang Yang <yang.yang29@zte.com.cn> wrote:
>
> > On Mon, Apr 17, 2023 at 1:12 AM <yang.yang29@zte.com.cn> wrote:
> >>
> >> From: Yang Yang <yang.yang19@zte.com.cn>
> >>
> >> Psi_group's poll_min_period is determined by the min window size of
> >> psi_trigger when creating new triggers. While destroying a psi_trigger,
> >> there is no need to reset poll_min_period if the destroying psi_trigger
> >> not had the min windows size, since in this condition poll_min_period
> >> will keep the same as before.
> >
> > Nice optimization.
> >
> >>
> >> Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
> >
> > Acked-by: Suren Baghdasaryan <surenb@google.com>
>
> Hi, would you please take a review?

I guess this is a ping for PeterZ to queue this patch in his tree.
Peter, any issues with accepting this patch?

> Thanks!