linux-kernel - Re: [PATCH v10 08/11] sched: replace capacity

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Message-ID: <CADcy93WdRjirmjYHOFp-J_==uEK=giQAe6nPS+Pj6QYafnwJJg@mail.gmail.com>
Date:	Fri, 27 Mar 2015 22:52:35 +0800
From:	Xunlei Pang <pang.xunlei@...aro.org>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>, preeti@...ux.vnet.ibm.com,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	kamalesh@...ux.vnet.ibm.com, riel@...hat.com,
	Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
	efault@....de, dietmar.eggemann@....com
Subject: Re: [PATCH v10 08/11] sched: replace capacity_factor by usage

Hi Vincent,

On 27 February 2015 at 23:54, Vincent Guittot
<vincent.guittot@...aro.org> wrote:
>  /**
> @@ -6432,18 +6435,19 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
>
>                 /*
>                  * In case the child domain prefers tasks go to siblings
> -                * first, lower the sg capacity factor to one so that we'll try
> +                * first, lower the sg capacity so that we'll try
>                  * and move all the excess tasks away. We lower the capacity
>                  * of a group only if the local group has the capacity to fit
> -                * these excess tasks, i.e. nr_running < group_capacity_factor. The
> -                * extra check prevents the case where you always pull from the
> -                * heaviest group when it is already under-utilized (possible
> -                * with a large weight task outweighs the tasks on the system).
> +                * these excess tasks. The extra check prevents the case where
> +                * you always pull from the heaviest group when it is already
> +                * under-utilized (possible with a large weight task outweighs
> +                * the tasks on the system).
>                  */
>                 if (prefer_sibling && sds->local &&
> -                   sds->local_stat.group_has_free_capacity) {
> -                       sgs->group_capacity_factor = min(sgs->group_capacity_factor, 1U);
> -                       sgs->group_type = group_classify(sg, sgs);
> +                   group_has_capacity(env, &sds->local_stat) &&
> +                   (sgs->sum_nr_running > 1)) {
> +                       sgs->group_no_capacity = 1;
> +                       sgs->group_type = group_overloaded;
>                 }
>

For SD_PREFER_SIBLING, if local has 1 task and group_has_capacity()
returns true(but not overloaded)  for it, and assume sgs group has 2
tasks, should we still mark this group overloaded?

-Xunlei
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