Re: [PATCH v3] mm: slub: only warn once when allocating slab obj extensions fails

[Harry Yoo <harry.yoo@oracle.com>]

On Fri, May 23, 2025 at 05:52:40PM +0100, Usama Arif wrote:
> In memory bound systems, a large number of warnings for failing this
> allocation repeatedly may mask any real issues in the system
> during memory pressure being reported in dmesg. Change this to
> warning only once.
> 
> Signed-off-by: Usama Arif <usamaarif642@gmail.com>
> Reported-by: Vlad Poenaru <vlad.wing@gmail.com>
> Closes: https://urldefense.com/v3/__https://lore.kernel.org/all/17fab2d6-5a74-4573-bcc3-b75951508f0a@gmail.com/__;!!ACWV5N9M2RV99hQ!Nv5xX_X4cBQR_HUDO6qfamxI0GEW1eFRCpPj29lANRashIUJDrEWAjU7vlys76FH0voShW07CjpDkzSST46Irg$ 
> ---

Acked-by: Harry Yoo <harry.yoo@oracle.com>

> v2 -> v3:
> - Put warning back, but only warn once with pr_warn_once.
> v1 -> v2:
> - remove the warning completely. We will have a way in the
>   future to indicate that the mem alloc profile is inaccurate.
> ---
>  mm/slub.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index dc9e729e1d26..36d7c43a6f2a 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2102,10 +2102,12 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
>  
>  	slab = virt_to_slab(p);
>  	if (!slab_obj_exts(slab) &&
> -	    WARN(alloc_slab_obj_exts(slab, s, flags, false),
> -		 "%s, %s: Failed to create slab extension vector!\n",
> -		 __func__, s->name))
> +	    alloc_slab_obj_exts(slab, s, flags, false)) {
> +		pr_warn_once("%s, %s: Failed to create slab extension vector!\n",
> +			__func__, s->name);
>  		return NULL;
> +	}
> +
>  
>  	return slab_obj_exts(slab) + obj_to_index(s, slab, p);
>  }
> -- 
> 2.47.1
> 

-- 
Cheers,
Harry / Hyeonggon