linux-kernel - Re: [PATCH] mm/list_lru: Optimize memcg_drain_list_lru

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Date:   Tue, 8 Mar 2022 10:41:38 -0500
From:   Waiman Long <longman@...hat.com>
To:     Roman Gushchin <roman.gushchin@...ux.dev>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: Re: [PATCH] mm/list_lru: Optimize memcg_drain_list_lru_node()

On 3/7/22 23:39, Roman Gushchin wrote:
> On Mon, Mar 07, 2022 at 10:30:09PM -0500, Waiman Long wrote:
>> Since commit 2c80cd57c743 ("mm/list_lru.c: fix list_lru_count_node()
>> to be race free"), we are tracking the total number of lru
>> entries in a list_lru_node in its nr_items field.  In the case of
>> memcg_drain_list_lru_node(), there is nothing to be done if nr_items
>> is 0.  We don't even need to take the nlru->lock as no new lru entry
>> could be added by a racing list_lru_add() to the draining src_idx memcg
>> at this point.
>>
>> Signed-off-by: Waiman Long <longman@...hat.com>
> Hi Waiman!
>
> The patch makes total sense to me, however it needs to be rebased at least
> on top of "mm: list_lru: rename memcg_drain_all_list_lrus to memcg_reparent_list_lrus".
>
> Thanks!
>
>
This patch was based on the current linux-next tree which includes 
commit ff221bc26bdd ("mm: list_lru: rename memcg_drain_all_list_lrus to 
memcg_reparent_list_lrus"). I do remember to double-check linux-next 
before sending this patch out. In fact, the same patch can be applied to 
both linux and linux-next tree without problem.

Cheers,
Longman