linux-kernel - Re: [PATCH v2 2/5] sched/numa: Replace runnable_load_avg by load

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Date:   Tue, 18 Feb 2020 17:41:19 +0000
From:   Mel Gorman <mgorman@...e.de>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        linux-kernel@...r.kernel.org, pauld@...hat.com,
        parth@...ux.ibm.com, hdanton@...a.com
Subject: Re: [PATCH v2 2/5] sched/numa: Replace runnable_load_avg by load_avg

On Tue, Feb 18, 2020 at 04:50:48PM +0000, Valentin Schneider wrote:
> On 18/02/2020 15:38, Mel Gorman wrote:
> >>
> >> Could we reuse group_type instead? The definitions are the same modulo
> >> s/group/node/.
> >>
> > 
> > I kept the naming because there is the remote possibility that NUMA
> > balancing will deviate in some fashion. Right now, it's harmless.
> > 
> 
> Since it's just a subset ATM I'd go for the reuse and change that later if
> shown a split is required, but fair enough.
> 

I would feel that I was churning code for the sake of it.

> > I didn't merge that part of the first version of my series. I was
> > waiting to see how the implementation for allowing a small degree of
> > imbalance looks like. If it's entirely confined in adjust_numa_balance
>                                                      ^^^^^^^^^^^^^^^^^^^
> Apologies if that's a newbie question, but I'm not familiar with that one.
> Would that be added in your reconciliation series? I've only had a brief
> look at it yet (it's next on the chopping block).
> 

I should have wrote adjust_numa_imbalance but yes, it's part of the
reconciled series so that NUMA balancing and the load balancer use the
same helper.

> > Yikes, no I'd rather not do that. Basically all I did before was create
> > a common helper like __lb_has_capacity that only took basic types as
> > parameters. group_has_capacity and numa_has_capacity were simple wrappers
> > that read the correct fields from their respective stats structures.
> > 
> 
> That's more sensible indeed. It'd definitely be nice to actually reconcile
> the two balancers with these common helpers, though I guess it doesn't
> *have* to happen with this very patch.

Yep, it can happen at a later time.

As it stands, I think the reconciled series stands on its own even
though there are further improvements that could be built on top.

-- 
Mel Gorman
SUSE Labs