linux-kernel - Re: [PATCH RFC 03/19] slub: remove CONFIG_SLUB

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Message-ID: <90f21264-b227-4a83-9944-39d3e0ea40dd@suse.cz>
Date: Wed, 29 Oct 2025 16:37:21 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>,
 Roman Gushchin <roman.gushchin@...ux.dev>, Harry Yoo <harry.yoo@...cle.com>,
 Uladzislau Rezki <urezki@...il.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Suren Baghdasaryan <surenb@...gle.com>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Alexei Starovoitov <ast@...nel.org>, linux-mm <linux-mm@...ck.org>,
 LKML <linux-kernel@...r.kernel.org>, linux-rt-devel@...ts.linux.dev,
 bpf <bpf@...r.kernel.org>, kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: [PATCH RFC 03/19] slub: remove CONFIG_SLUB_TINY specific code
 paths

On 10/25/25 00:34, Alexei Starovoitov wrote:
> On Thu, Oct 23, 2025 at 6:53 AM Vlastimil Babka <vbabka@...e.cz> wrote:
>>
>> CONFIG_SLUB_TINY minimizes the SLUB's memory overhead in multiple ways,
>> mainly by avoiding percpu caching of slabs and objects. It also reduces
>> code size by replacing some code paths with simplified ones through
>> ifdefs, but the benefits of that are smaller and would complicate the
>> upcoming changes.
>>
>> Thus remove these code paths and associated ifdefs and simplify the code
>> base.
>>
>> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
>> ---
>>  mm/slab.h |   2 --
>>  mm/slub.c | 107 +++-----------------------------------------------------------
>>  2 files changed, 4 insertions(+), 105 deletions(-)
> 
> Looks like it is removing most of it.

The special code, yes. But the savings from avoiding percpu caching are the
most important anyway and they stay.

> Just remove the whole thing. Do people care about keeping SLUB_TINY?

They did when SLOB was being removed. We can always remove it completely
later, but this code cleanup is enough for me not to complicate the further
changes, so I wouldn't want to put the complete removal in this series.