linux-kernel - Re: [PATCH 07/12] mm, slab: ignore SLAB_RECLAIM_ACCOUNT with CONFIG_SLUB

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Date:   Wed, 23 Nov 2022 17:20:04 -0800
From:   Roman Gushchin <roman.gushchin@...ux.dev>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Pekka Enberg <penberg@...nel.org>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>, patches@...ts.linux.dev,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/12] mm, slab: ignore SLAB_RECLAIM_ACCOUNT with
 CONFIG_SLUB_TINY

On Mon, Nov 21, 2022 at 06:11:57PM +0100, Vlastimil Babka wrote:
> SLAB_RECLAIM_ACCOUNT caches allocate their slab pages with
> __GFP_RECLAIMABLE and can help against fragmentation by grouping pages
> by mobility, but on tiny systems mobility grouping is likely disabled
> anyway and ignoring SLAB_RECLAIM_ACCOUNT might instead lead to merging
> of caches that are made incompatible just by the flag.
> 
> Thus with CONFIG_SLUB_TINY, make SLAB_RECLAIM_ACCOUNT ineffective.

Hm, do you see disabling all kernel memory accounting functionality
with COFNIG_SLUB_TINY? I'd say yes. But in this case need to be consistent
and disable it alltogether.

Thanks!