From: Hao Li <hao.li@linux.dev>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: Harry Yoo <harry@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Shakeel Butt <shakeel.butt@linux.dev>,
Alexander Potapenko <glider@google.com>,
Marco Elver <elver@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Christoph Lameter <cl@gentwo.org>,
David Rientjes <rientjes@google.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
cgroups@vger.kernel.org
Subject: Re: [PATCH v2 13/13] mm/slab: stop allocating objcg pointers when unnecessary
Date: Fri, 24 Jul 2026 17:57:15 +0800 [thread overview]
Message-ID: <amM2ybmTYfjlvDV7@fedora> (raw)
In-Reply-To: <20260720-b4-objext_split-v2-13-2fa7c6f60dbe@kernel.org>
On Mon, Jul 20, 2026 at 04:16:27PM +0200, Vlastimil Babka (SUSE) wrote:
> Start using the slab_needs_objcg() helper to calculate slabobj_ext size.
> Caches that we know to never need objcg pointers (currently
> KMALLOC_NORMAL caches) will thus stop wasting memory on them when memory
> allocation profiling is enabled.
>
> For things to work properly, we need to also add slab_needs_objcg()
> checks to mem_cgroup_from_obj_slab() and memcg_slab_free_hook(), because
> when obj_exts array exists for a slab only due to mem_alloc profiling,
> we would otherwise attempt to access a non-existing objcg pointer in
> that slab.
>
> The function __memcg_slab_post_alloc_hook() should not be possible to
> call for a slab where slab_needs_objcg() is false, but add a DEBUG_VM
> check there to prevent breaking this assumption accidentally.
>
> Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Looks good to me.
Reviewed-by: Hao Li <hao.li@linux.dev>
--
Thanks,
Hao
prev parent reply other threads:[~2026-07-24 9:57 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-20 14:16 [PATCH v2 00/13] mm/slab, alloc_tag: reduce obj_ext memory waste Vlastimil Babka (SUSE)
2026-07-20 14:16 ` [PATCH v2 01/13] mm/slab: skip kfence objects in allocation profiling Vlastimil Babka (SUSE)
2026-07-21 5:43 ` Harry Yoo
2026-07-21 9:20 ` Vlastimil Babka (SUSE)
2026-07-21 15:41 ` Harry Yoo
2026-07-22 12:47 ` Hao Li
2026-07-24 15:58 ` Vlastimil Babka (SUSE)
2026-07-27 6:21 ` Hao Li
2026-07-20 14:16 ` [PATCH v2 02/13] mm/slub: skip handle_failed_objexts_alloc() with profiling disabled Vlastimil Babka (SUSE)
2026-07-21 5:51 ` Harry Yoo
2026-07-21 9:23 ` Vlastimil Babka (SUSE)
2026-07-20 14:16 ` [PATCH v2 03/13] mm/slab: remove objs_per_slab() Vlastimil Babka (SUSE)
2026-07-21 5:53 ` Harry Yoo
2026-07-23 11:29 ` Hao Li
2026-07-20 14:16 ` [PATCH v2 04/13] mm: move struct slabobj_ext to mm/slab.h Vlastimil Babka (SUSE)
2026-07-21 5:55 ` Harry Yoo
2026-07-23 11:29 ` Hao Li
2026-07-20 14:16 ` [PATCH v2 05/13] mm/slab: make slab_obj_ext() determine object index Vlastimil Babka (SUSE)
2026-07-21 6:02 ` Harry Yoo
2026-07-23 11:30 ` Hao Li
2026-07-20 14:16 ` [PATCH v2 06/13] mm/slab: abstract slabobj_ext.objcg access Vlastimil Babka (SUSE)
2026-07-23 11:32 ` Hao Li
2026-07-23 17:23 ` Suren Baghdasaryan
2026-07-20 14:16 ` [PATCH v2 07/13] mm/slab: abstract slabobj_ext.ref access Vlastimil Babka (SUSE)
2026-07-23 11:32 ` Hao Li
2026-07-20 14:16 ` [PATCH v2 08/13] mm/slab: replace slab.stride with obj_exts_in_object Vlastimil Babka (SUSE)
2026-07-23 11:32 ` Hao Li
2026-07-20 14:16 ` [PATCH v2 09/13] mm/slab: change struct slabobj_ext to a union Vlastimil Babka (SUSE)
2026-07-23 3:05 ` Hao Li
2026-07-23 6:27 ` Harry Yoo
2026-07-23 9:56 ` Hao Li
2026-07-24 15:42 ` Vlastimil Babka (SUSE)
2026-07-27 5:41 ` Harry Yoo
2026-07-27 6:22 ` Hao Li
2026-07-20 14:16 ` [PATCH v2 10/13] mm/slab: introduce slab_obj_ext_has_codetag() Vlastimil Babka (SUSE)
2026-07-20 14:16 ` [PATCH v2 11/13] mm/slab: reduce slabobj_ext memory with allocation profiling disabled Vlastimil Babka (SUSE)
2026-07-20 14:16 ` [PATCH v2 12/13] mm/slab: add cache_ and slab_needs_objcg() helpers Vlastimil Babka (SUSE)
2026-07-23 9:25 ` Hao Li
2026-07-23 9:30 ` Vlastimil Babka (SUSE)
2026-07-23 10:01 ` Hao Li
2026-07-24 9:41 ` Hao Li
2026-07-24 16:31 ` Vlastimil Babka (SUSE)
2026-07-27 6:17 ` Hao Li
2026-07-24 16:38 ` Vlastimil Babka (SUSE)
2026-07-20 14:16 ` [PATCH v2 13/13] mm/slab: stop allocating objcg pointers when unnecessary Vlastimil Babka (SUSE)
2026-07-24 9:57 ` Hao Li [this message]
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