linux-kernel - Re: [PATCH v3 04/10] sched/fair: rework load

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Message-ID: <36d904ff-44fa-a561-677d-4858d5921b69@arm.com>
Date:   Tue, 1 Oct 2019 18:57:06 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Phil Auld <pauld@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Quentin Perret <quentin.perret@....com>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        Hillf Danton <hdanton@...a.com>
Subject: Re: [PATCH v3 04/10] sched/fair: rework load_balance



On 01/10/2019 11:14, Vincent Guittot wrote:
> group_asym_packing
> 
> On Tue, 1 Oct 2019 at 10:15, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
>>
>> On 19/09/2019 09:33, Vincent Guittot wrote:
>>
>>
>> [...]
>>
>>> @@ -8042,14 +8104,24 @@ static inline void update_sg_lb_stats(struct lb_env *env,
>>>               }
>>>       }
>>>
>>> -     /* Adjust by relative CPU capacity of the group */
>>> +     /* Check if dst cpu is idle and preferred to this group */
>>> +     if (env->sd->flags & SD_ASYM_PACKING &&
>>> +         env->idle != CPU_NOT_IDLE &&
>>> +         sgs->sum_h_nr_running &&
>>> +         sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu)) {
>>> +             sgs->group_asym_packing = 1;
>>> +     }
>>> +
>>
>> Since asym_packing check is done per-sg rather per-CPU (like misfit_task), can you
>> not check for asym_packing in group_classify() directly (like for overloaded) and
>> so get rid of struct sg_lb_stats::group_asym_packing?
> 
> asym_packing uses a lot of fields of env to set group_asym_packing but
> env is not statistics and i'd like to remove env from
> group_classify() argument so it will use only statistics.
> At now, env is an arg of group_classify only for imbalance_pct field
> and I have replaced env by imabalnce_pct in a patch that is under
> preparation.
> With this change, I can use group_classify outside load_balance()

OK, I see. This relates to the 'update find_idlest_group() to be more
aligned with load_balance()' point mentioned in the cover letter I
assume. To make sure we can use load instead of runnable_load there as well.

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