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

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Date:   Thu, 2 Nov 2023 10:10:53 +0800
From:   Chengming Zhou <chengming.zhou@...ux.dev>
To:     Vlastimil Babka <vbabka@...e.cz>, 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 2023/11/1 21:21, Vlastimil Babka wrote:
> 
> 
> 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.

Ok, I will delete it in v5.

Thanks!