Re: [PATCH v3 2/2] mm, slab: simplify returning slab in __refill_objects_node()

[Hao Li <hao.li@linux.dev>]

On Fri, May 22, 2026 at 04:23:21PM +0200, Vlastimil Babka (SUSE) wrote:
> When we return slabs to the partial list because we didn't fully refill
> from them, we observe the min_partial limit when the returned slab is
> empty, and discard it when over the limit. But it's unlikely for the
> limit to be reached while we were refilling, and the worst outcome is to
> have temporarily more free slabs on the list than necessary.

Just wondering if the empty slabs temporarily exceed the limit and then some
objects get allocated from them, would this lead to more fragmented slabs in
the node partial list?

> So just
> drop that code and simplify the function.
> 
> Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
> ---
>  mm/slub.c | 10 ----------
>  1 file changed, 10 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 5816fcfc7a90..074d57c0390b 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -7196,21 +7196,11 @@ __refill_objects_node(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int mi
>  
>  		list_for_each_entry_safe(slab, slab2, &pc.slabs, slab_list) {
>  
> -			if (unlikely(!slab->inuse && n->nr_partial >= s->min_partial))
> -				continue;
> -
>  			list_del(&slab->slab_list);
>  			add_partial(n, slab, ADD_TO_TAIL);
>  		}
>  
>  		spin_unlock_irqrestore(&n->list_lock, flags);
> -
> -		/* any slabs left are completely free and for discard */
> -		list_for_each_entry_safe(slab, slab2, &pc.slabs, slab_list) {
> -
> -			list_del(&slab->slab_list);
> -			discard_slab(s, slab);
> -		}
>  	}
>  
>  	return refilled;
> 
> -- 
> 2.54.0
> 

-- 
Thanks,
Hao