linux-kernel - Re: [PATCH v4 04/11] sched/fair: rework load

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Message-ID: <20191118135017.GA123637@gmail.com>
Date:   Mon, 18 Nov 2019 14:50:17 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        linux-kernel@...r.kernel.org, mingo@...hat.com,
        peterz@...radead.org, pauld@...hat.com, valentin.schneider@....com,
        srikar@...ux.vnet.ibm.com, quentin.perret@....com,
        dietmar.eggemann@....com, Morten.Rasmussen@....com,
        hdanton@...a.com, parth@...ux.ibm.com, riel@...riel.com
Subject: Re: [PATCH v4 04/11] sched/fair: rework load_balance


* Mel Gorman <mgorman@...hsingularity.net> wrote:

> s/groupe_type/group_type/
> 
> >  enum group_type {
> > -	group_other = 0,
> > +	group_has_spare = 0,
> > +	group_fully_busy,
> >  	group_misfit_task,
> > +	group_asym_packing,
> >  	group_imbalanced,
> > -	group_overloaded,
> > +	group_overloaded
> > +};
> > +
> 
> While not your fault, it would be nice to comment on the meaning of each
> group type. From a glance, it's not obvious to me why a misfit task should
> be a high priority to move a task than a fully_busy (but not overloaded)
> group given that moving the misfit task might make a group overloaded.

This part of your feedback should now be addressed in the scheduler tree 
via:

  a9723389cc75: sched/fair: Add comments for group_type and balancing at SD_NUMA level

> > +enum migration_type {
> > +	migrate_load = 0,
> > +	migrate_util,
> > +	migrate_task,
> > +	migrate_misfit
> >  };
> >  
> 
> Could do with a comment explaining what migration_type is for because
> the name is unhelpful. I *think* at a glance it's related to what sort
> of imbalance is being addressed which is partially addressed by the
> group_type. That understanding may change as I continue reading the series
> but now I have to figure it out which means it'll be forgotten again in
> 6 months.

Agreed. Vincent, is any patch brewing here, or should I take a stab?

Thanks,

	Ingo