linux-kernel - Re: [PATCH] mm/slab: add new flag SLAB_NO

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Date:   Thu, 25 May 2023 14:05:25 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Hyeonggon Yoo <42.hyeyoo@...il.com>,
        David Sterba <dsterba@...e.com>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Roman Gushchin <roman.gushchin@...ux.dev>
Subject: Re: [PATCH] mm/slab: add new flag SLAB_NO_MERGE to avoid merging per
 slab

On Wed, May 24, 2023 at 03:53:11PM +0200, Vlastimil Babka wrote:
> On 5/24/23 14:56, Hyeonggon Yoo wrote:
> > On Wed, May 24, 2023 at 12:17:48PM +0200, David Sterba wrote:
> > work for your use case? (there are some boot-time slub_debug options described in
> > Documentation/mm/slub.rst)
> 
> Yeah, it supports globbing so it would be e.g. slub_debug=N,btrfs*
> That would deal with the "too coarse" aspect slab_nomerge. As for "need to
> be enabled on all testing hosts", is it more convenient to deploy a debug
> kernel build on them? Might be because you do that for other reasons
> already? Just want to clarify.

Yeah, agreed.

> BTW this was proposed as RFC few months ago but not pursued:
> https://lore.kernel.org/all/167396280045.539803.7540459812377220500.stgit@firesoul/
> 
> I have no big objections, just wouldn't like to see its usage proliferate
> unconditionally into non-debug builds.

It would be fine for me to make it conditionally available, e.g.
depending on SLUB_DEBUG.