linux-kernel - Re: [PATCH 1/4] mm/slub: remove the check of !kmem_cache_has_cpu

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Message-ID: <d5a7f24c-52e6-471c-893e-44448efccbd4@suse.cz>
Date: Tue, 2 Apr 2024 11:45:45 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: xiongwei.song@...driver.com, rientjes@...gle.com, cl@...ux.com,
 penberg@...nel.org, iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
 roman.gushchin@...ux.dev, 42.hyeyoo@...il.com
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, chengming.zhou@...ux.dev
Subject: Re: [PATCH 1/4] mm/slub: remove the check of
 !kmem_cache_has_cpu_partial()

On 3/31/24 4:19 AM, xiongwei.song@...driver.com wrote:
> From: Xiongwei Song <xiongwei.song@...driver.com>
> 
> The check of !kmem_cache_has_cpu_partial(s) with
> CONFIG_SLUB_CPU_PARTIAL enabled here is always false. We have known the
> result by calling kmem_cacke_debug(). Here we can remove it.

Could we be more obvious. We have already checked kmem_cache_debug() earlier
and if it was true, the we either continued or broke from the loop so we
can't reach this code in that case and don't need to check
kmem_cache_debug() as part of kmem_cache_has_cpu_partial() again.

> Signed-off-by: Xiongwei Song <xiongwei.song@...driver.com>
> ---
>  mm/slub.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 1bb2a93cf7b6..059922044a4f 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2610,8 +2610,7 @@ static struct slab *get_partial_node(struct kmem_cache *s,
>  			partial_slabs++;
>  		}
>  #ifdef CONFIG_SLUB_CPU_PARTIAL
> -		if (!kmem_cache_has_cpu_partial(s)
> -			|| partial_slabs > s->cpu_partial_slabs / 2)
> +		if (partial_slabs > s->cpu_partial_slabs / 2)
>  			break;
>  #else
>  		break;