linux-kernel - Re: [PATCH] sched: Call update_group_power only for local

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Message-ID: <AANLkTinCWjyfsMeMTMZeYTcLgYD3LMKviOi_PNXWHUou@mail.gmail.com>
Date:	Mon, 12 Jul 2010 10:11:56 -0700
From:	Venkatesh Pallipadi <venki@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Suresh Siddha <suresh.b.siddha@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Gautham R Shenoy <ego@...ibm.com>,
	Joel Schopp <jschopp@...tin.ibm.com>,
	Michael Neuling <mikey@...ling.org>
Subject: Re: [PATCH] sched: Call update_group_power only for local_group

On Thu, Jul 8, 2010 at 11:16 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Thu, 2010-07-08 at 10:45 -0700, Suresh Siddha wrote:
>> > @@ -2433,7 +2433,8 @@ static inline void update_sg_lb_stats(struct sched_domain *sd,
>> >               return;
>> >       }
>> >
>> > -     update_group_power(sd, this_cpu);
>> > +     if (local_group)
>> > +             update_group_power(sd, this_cpu);
>>
>> if IDLE == CPU_NEWLY_IDLE, then all the cpu's in the local group will do
>> this. Also update_group_power() can be done on only on the local cpu,
>> i.e., when this_cpu == smp_processor_id() right?
>
> It might make sense to only update_group_power on !CPU_NEWLY_IDLE and
> rely on the tick driven cpu_power updates.
>
> No sense in updating them in finer slices I guess.
>
> So how about something like:

Yes. This looks good.

Acked-by: Venkatesh Pallipadi <venki@...gle.com>

>
> ---
>  kernel/sched_fair.c |   12 ++++++------
>  1 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
> index 9910e1b..2f05679 100644
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -2427,14 +2427,14 @@ static inline void update_sg_lb_stats(struct sched_domain *sd,
>         * domains. In the newly idle case, we will allow all the cpu's
>         * to do the newly idle load balance.
>         */
> -       if (idle != CPU_NEWLY_IDLE && local_group &&
> -           balance_cpu != this_cpu) {
> -               *balance = 0;
> -               return;
> +       if (idle != CPU_NEWLY_IDLE && local_group) {
> +               if (balance_cpu != this_cpu) {
> +                       *balance = 0;
> +                       return;
> +               }
> +               update_group_power(sd, this_cpu);
>        }
>
> -       update_group_power(sd, this_cpu);
> -
>        /* Adjust by relative CPU power of the group */
>        sgs->avg_load = (sgs->group_load * SCHED_LOAD_SCALE) / group->cpu_power;
>
>
>
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