linux-kernel - Re: Do we really need SLOB nowdays?

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Date:   Wed, 15 Dec 2021 16:23:04 +0100 (CET)
From:   Christoph Lameter <cl@...two.org>
To:     Vlastimil Babka <vbabka@...e.cz>
cc:     Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Matthew Wilcox <willy@...radead.org>,
        Christoph Lameter <cl@...two.de>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Do we really need SLOB nowdays?

On Wed, 15 Dec 2021, Vlastimil Babka wrote:

> > SLOB:
> >
> > 	Memory required to boot: 6950K
> >
> > 		Slab:                368 kB
> >
> > SLUB:
> > 	Memory required to boot: 6800K
> >
> > 		Slab:                552 kB
> >
> > SLUB with slab merging:
> >
> > 		Slab:                536 kB
>
> 168kB different on a system with less than 8MB memory looks rather
> significant to me to simply delete SLOB, I'm afraid.

This looks more like a bug/difference in SLAB accounting of SLOB.

How could SLOB require more memory to boot but use less SLAB memory?

This looks to me like a significant reason enough to remove SLOB since
SLUB works with less memory than SLOB.