linux-kernel - Re: [PATCH] mm/slub: remove dead code for debug caches on deactivate

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Date:   Mon, 24 Oct 2022 13:10:57 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Hyeonggon Yoo <42.hyeyoo@...il.com>
Cc:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/slub: remove dead code for debug caches on
 deactivate_slab()

On 10/22/22 06:14, Hyeonggon Yoo wrote:
> On Fri, Oct 21, 2022 at 12:43:42PM +0200, Vlastimil Babka wrote:
>> On 10/14/22 13:43, Hyeonggon Yoo wrote:
>> > After commit c7323a5ad0786 ("mm/slub: restrict sysfs validation to debug
>> > caches and make it safe"), SLUB does not take a slab from partial list for
>> 
>> I'm confused by "SLUB does not take a slab from partial list" here. Did you
>> mean something like "SLUB never installs (even temporarily) a percpu slab
>> for debug caches"?
> 
> Yes.
> 
>> So that means we never deactivate percpu slabs for debug
>> caches.
> 
> Yes.
> 
>> And since debug caches are also the only ones that use the full
>> list, we no longer need to care about the full list in deactivate_slab(), right?
> 
> Yes, You got it right, exactly!
> 
> Let me rephrase:
> 
> "After commit c7323a5ad0786 ("mm/slub: restrict sysfs validation to debug
> caches and make it safe"), SLUB never installs percpu slab for debug caches
> and thus never deactivates percpu slab for them.
> 
> Since only some of debug caches care about the full list, SLUB no longer
> deactivates to full list. Remove dead code in deactivate_slab()."
> 
> 
> Feel free to change this ;-)

Great, thanks!

Pushed to slab/for-6.2/cleanups