linux-kernel - Re: [PATCH v4 11/22] slab: remove cpu (partial) slabs usage from allocation paths

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Message-ID: <CAADnVQKbuLD=gaC1W9gtXrj9VdwQCqt2f_rtYwF1Tc1RcUOjKg@mail.gmail.com>
Date: Fri, 23 Jan 2026 10:17:37 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Harry Yoo <harry.yoo@...cle.com>, Petr Tesarik <ptesarik@...e.com>, 
	Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Hao Li <hao.li@...ux.dev>, 
	Andrew Morton <akpm@...ux-foundation.org>, 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>, 
	"open list:Real-time Linux (PREEMPT_RT):Keyword:PREEMPT_RT" <linux-rt-devel@...ts.linux.dev>, bpf <bpf@...r.kernel.org>, 
	kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: [PATCH v4 11/22] slab: remove cpu (partial) slabs usage from
 allocation paths

On Thu, Jan 22, 2026 at 10:54 PM Vlastimil Babka <vbabka@...e.cz> wrote:
>
> We now rely on sheaves as the percpu caching layer and can refill them
> directly from partial or newly allocated slabs. Start removing the cpu
> (partial) slabs code, first from allocation paths.
>
> This means that any allocation not satisfied from percpu sheaves will
> end up in ___slab_alloc(), where we remove the usage of cpu (partial)
> slabs, so it will only perform get_partial() or new_slab(). In the
> latter case we reuse alloc_from_new_slab() (when we don't use
> the debug/tiny alloc_single_from_new_slab() variant).
>
> In get_partial_node() we used to return a slab for freezing as the cpu
> slab and to refill the partial slab. Now we only want to return a single
> object and leave the slab on the list (unless it became full). We can't
> simply reuse alloc_single_from_partial() as that assumes freeing uses
> free_to_partial_list(). Instead we need to use __slab_update_freelist()
> to work properly against a racing __slab_free().
>
> To reflect the new purpose of get_partial() functions, rename them to
> get_from_partial(), get_from_partial_node(), and get_from_any_partial().
>
> The rest of the changes is removing functions that no longer have any
> callers.
>
> Reviewed-by: Harry Yoo <harry.yoo@...cle.com>
> Reviewed-by: Hao Li <hao.li@...ux.dev>
> Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> ---
>  mm/slub.c | 628 +++++++++-----------------------------------------------------
>  1 file changed, 87 insertions(+), 541 deletions(-)

so much simpler. love the red diff.

Acked-by: Alexei Starovoitov <ast@...nel.org>