linux-kernel - Re: [RFC PATCH v4 7/9] slub: Optimize deactivate

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Message-ID: <6041f645-a3d0-367a-8f2a-c6c5a68507ca@suse.cz>
Date:   Wed, 1 Nov 2023 14:21:01 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     chengming.zhou@...ux.dev, cl@...ux.com, penberg@...nel.org,
        willy@...radead.org
Cc:     rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, roman.gushchin@...ux.dev,
        42.hyeyoo@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Chengming Zhou <zhouchengming@...edance.com>
Subject: Re: [RFC PATCH v4 7/9] slub: Optimize deactivate_slab()



On 10/31/23 15:07, chengming.zhou@...ux.dev wrote:
> From: Chengming Zhou <zhouchengming@...edance.com>
> 
> Since the introduce of unfrozen slabs on cpu partial list, we don't
> need to synchronize the slab frozen state under the node list_lock.
> 
> The caller of deactivate_slab() and the caller of __slab_free() won't
> manipulate the slab list concurrently.
> 
> So we can get node list_lock in the last stage if we really need to
> manipulate the slab list in this path.
> 
> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>

Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  mm/slub.c | 76 +++++++++++++++++++------------------------------------
>  1 file changed, 26 insertions(+), 50 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index bcb5b2c4e213..c429f8baba5f 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2468,10 +2468,8 @@ static void init_kmem_cache_cpus(struct kmem_cache *s)
>  static void deactivate_slab(struct kmem_cache *s, struct slab *slab,
>  			    void *freelist)
>  {
> -	enum slab_modes { M_NONE, M_PARTIAL, M_FREE, M_FULL_NOLIST };
>  	struct kmem_cache_node *n = get_node(s, slab_nid(slab));
>  	int free_delta = 0;
> -	enum slab_modes mode = M_NONE;
>  	void *nextfree, *freelist_iter, *freelist_tail;
>  	int tail = DEACTIVATE_TO_HEAD;
>  	unsigned long flags = 0;
> @@ -2512,62 +2510,40 @@ static void deactivate_slab(struct kmem_cache *s, struct slab *slab,
>  	 *
>  	 * Ensure that the slab is unfrozen while the list presence
>  	 * reflects the actual number of objects during unfreeze.

I think this we can delete also these two lines. If there's no other
reason for v5, I can do it when merging the series.