linux-kernel - Re: [QUESTION] is SLAB considered legacy and deprecated?

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Date:   Tue, 5 Oct 2021 13:31:02 +0000
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [QUESTION] is SLAB considered legacy and deprecated?

On Mon, Oct 04, 2021 at 01:39:46PM +0200, Vlastimil Babka wrote:
> On 10/4/21 08:01, Hyeonggon Yoo wrote:
> > On Sun, Oct 03, 2021 at 06:25:29PM -0700, David Rientjes wrote:
> >> I would disagree that SLAB isn't currently maintained, I think it's 
> >> actively maintained.
> > 
> > I thought it was not actively maintained because most of patches were
> > fixups and cleanups for years and as Vlastimil said, new features are
> 
> Fixups and cleanups still count as "actively maintained". The opposite
> case would be "nobody uses it because it was broken for years since
> commit X and we only noticed now".
>

Yup, there seems I was differently using meaning of "actively
maintained".

> > only added to SLUB. development was focused on SLUB.
> > 
> >> I think the general guidance is that changes for both allocators can still
> >> be merged upstream if they show a significant win (improved performnace, 
> >> maintaining performance while reducing memory footprint, code hygiene, 
> >> etc) and there's no specific policy that we cannot make changes to 
> >> mm/slab.c.
> > 
> > Good.
> > 
> > I see things to improve in SLAB and want to improve it.
> > I will appreciate if you review them.
>
> It would be great if your motivation started with "I prefer SLAB over
> SLUB because X and Y but I need to improve Z", not just a theoretical
> concern.
> 

Thank you for advice. by making dumb patches I realized that
, yeah, just a theoretical concern does not help.

I should have more understanding on internals of slab allocators
and on how their characteristics affect performance depending on situation.
and most importantly I should have actual evidence of performance measurement.

I'm sorry and Thank you for thinking about and answering my (somewhat dumb) questions.
But I'm happy that I'm learning a lot from your feedback.

> > Thanks,
> > Hyeonggon
> > 
>