linux-kernel - Re: [PATCH 10/12] mm, slub: remove percpu slabs with CONFIG_SLUB

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Date:   Sun, 27 Nov 2022 20:05:52 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
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>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>, patches@...ts.linux.dev,
        Dennis Zhou <dennis@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 10/12] mm, slub: remove percpu slabs with CONFIG_SLUB_TINY

On Mon, Nov 21, 2022 at 06:12:00PM +0100, Vlastimil Babka wrote:
> SLUB gets most of its scalability by percpu slabs. However for
> CONFIG_SLUB_TINY the goal is minimal memory overhead, not scalability.
> Thus, #ifdef out the whole kmem_cache_cpu percpu structure and
> associated code. Additionally to the slab page savings, this reduces
> percpu allocator usage, and code size.

[+Cc Dennis]

Wondering if we can reduce (or zero) early reservation of percpu area
when #if !defined(CONFIG_SLUB) || defined(CONFIG_SLUB_TINY)?

> This change builds on recent commit c7323a5ad078 ("mm/slub: restrict
> sysfs validation to debug caches and make it safe"), as caches with
> enabled debugging also avoid percpu slabs and all allocations and
> freeing ends up working with the partial list. With a bit more
> refactoring by the preceding patches, use the same code paths with
> CONFIG_SLUB_TINY.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>

-- 
Thanks,
Hyeonggon