Re: [PATCH V1 0/2] Only allow SLAB_OBJ_EXT_IN_OBJ for unmergeable caches

[Vlastimil Babka <vbabka@suse.cz>]

On 1/27/26 11:31, Harry Yoo wrote:
> While SLAB_OBJ_EXT_IN_OBJ allows to reduce memory overhead to account
> slab objects, it prevents slab merging because merging can change
> the metadata layout.
> 
> As pointed out Vlastimil Babka, disabling merging solely for this memory
> optimization may not be a net win, because disabling slab merging tends
> to increase overall memory usage.
> 
> So let's take a conservative approach and restrict SLAB_OBJ_EXT_IN_OBJ
> to caches that are already unmergeable for other reasons.
> 
> Ideally this should be part of the slab/for-7.0/obj_metadata branch,
> but due to a conflict with slab/for-7.0/sheaves, I based it on
> slab/for-next (be36abd97e52).
> 
> Patch 1 factors out mergeability logic to slab_args_unmergeable().
> This is used to determine mergeability before the cache is created.
> 
> Patch 2 uses the new function to allow SLAB_OBJ_EXT_IN_OBJ
> only when merging is not allowed for other reasons.
> 
> Harry Yoo (2):
>   mm/slab: factor out slab_args_unmergeable()
>   mm/slab: only allow SLAB_OBJ_EXT_IN_OBJ for unmergeable caches

Thanks, applied to slab/for-next and reorganized the sub-branches a bit to
prevent conflicts.

>  mm/slab.h        |  1 +
>  mm/slab_common.c | 27 +++++++++++++++++----------
>  mm/slub.c        |  3 ++-
>  3 files changed, 20 insertions(+), 11 deletions(-)
>