Re: [PATCH v3 06/10] mm, slab: make SLUB_TINY handling dynamic for sizing decisions

[Harry Yoo <harry@kernel.org>]

On Thu, Nov 05, 2026 at 09:43:55AM +0100, Vlastimil Babka (SUSE) wrote:
> Enabling CONFIG_SLUB_TINY results in the caches' min partial slabs
> threshold to be zero, thus every slab where all objects become free is
> freed immediately. It also sets the default slab_max_order to 1, with
> the goal of reducing the potential of internal slab fragmentation.
> 
> Rework both of these decisions to be based on the newly introduced
> slab_tiny_enabled flag instead of #ifdefs. It's still possible to
> override the reduced slab_max_order with the boot parameter, as before.
> 
> Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
> ---
>
>  mm/slub.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index a3ee1bdf0eb3..be4e1f193295 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -8027,7 +8021,7 @@ static unsigned int calculate_sheaf_capacity(struct kmem_cache *s,
>  	size_t size;
>  
>  
> -	if (IS_ENABLED(CONFIG_SLUB_TINY) || s->flags & SLAB_DEBUG_FLAGS)
> +	if (slab_tiny_enabled || s->flags & SLAB_DEBUG_FLAGS)
>  		return 0;

nit: this change is not mentioned in the changelog

Otherwise looks good to me,
Reviewed-by: Harry Yoo (Meta) <harry@kernel.org>

-- 
Cheers,
Harry / Hyeonggon