From mboxrd@z Thu Jan  1 00:00:00 1970
From: vincent.guittot@linaro.org (Vincent Guittot)
Date: Thu, 9 Oct 2014 16:18:02 +0200
Subject: [PATCH v7 6/7] sched: replace capacity_factor by usage
In-Reply-To: <20141009121643.GQ4750@worktop.programming.kicks-ass.net>
References: <1412684017-16595-1-git-send-email-vincent.guittot@linaro.org>
 <1412684017-16595-7-git-send-email-vincent.guittot@linaro.org>
 <20141009121643.GQ4750@worktop.programming.kicks-ass.net>
Message-ID: <CAKfTPtCX687FkGgxLO7spfGvDxhDWeFDERLRZ-NakO2Jrpmnhw@mail.gmail.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 9 October 2014 14:16, Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, Oct 07, 2014 at 02:13:36PM +0200, Vincent Guittot wrote:
>> +static inline bool
>> +group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
>>  {
>> +     if ((sgs->group_capacity * 100) >
>> +                     (sgs->group_usage * env->sd->imbalance_pct))
>> +             return true;
>
> Why the imb_pct there? We're looking for 100% utilization, not 130 or
> whatnot, right?

Having exactly 100% is quite difficult because of various rounding.
So i have added a margin/threshold to prevent any excessive change of the state.
I have just to use the same margin/threshold than in other place in
load balance.

so the current threshold depends of the sched_level. it's around 14% at MC level

>
>> +     if (sgs->sum_nr_running < sgs->group_weight)
>> +             return true;
>
> With the code as it stands, this is the cheaper test (no mults) so why
> is it second?
>
>> +     return false;
>> +}
>>
>> +static inline bool
>> +group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
>> +{
>> +     if (sgs->sum_nr_running <= sgs->group_weight)
>> +             return false;
>> +
>> +     if ((sgs->group_capacity * 100) <
>> +                     (sgs->group_usage * env->sd->imbalance_pct))
>> +             return true;
>>
>> +     return false;
>>  }
>
> Same thing here wrt imb_pct