linux-kernel - Re: [PATCH 3/5] mm/slab: Do not call kmalloc

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Message-ID: <10429c77-9492-bf9f-be6f-94e52393213e@suse.cz>
Date:   Thu, 24 Feb 2022 16:08:31 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Hyeonggon Yoo <42.hyeyoo@...il.com>
Cc:     linux-mm@...ck.org, Roman Gushchin <guro@...com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Joonsoo Kim <iamjoonsoo.kim@....com>,
        David Rientjes <rientjes@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH 3/5] mm/slab: Do not call kmalloc_large() for unsupported
 size

On 2/24/22 14:31, Hyeonggon Yoo wrote:
> On Thu, Feb 24, 2022 at 01:48:47PM +0100, Vlastimil Babka wrote:
>> On 2/21/22 11:53, Hyeonggon Yoo wrote:
>> > SLAB's kfree() does not support freeing an object that is allocated from
>> > kmalloc_large(). Fix this as SLAB do not pass requests larger than
>> > KMALLOC_MAX_CACHE_SIZE directly to page allocator.
>> 
>> AFAICS this issue is limited to build-time constant sizes. Might be better
>> to make this a build error rather than build-time NULL?
> 
> Right. And sounds better. But what about another direction as Matthew said:
> passing large requests to page allocator like SLUB?

Sounds like a good idea, that would reduce the number of kmalloc caches with
SLAB, and I expect also simplify the common code further.

> I think it's better for maintenance. Any obstacles for this direction?
> 
> Thank you!
> 
>> > Signed-off-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
>