Re: [PATCH] mm/list_lru: Optimize memcg_drain_list_lru_node()

[Waiman Long <longman@redhat.com>]

On 3/8/22 19:17, Roman Gushchin wrote:
> On Tue, Mar 08, 2022 at 10:41:38AM -0500, Waiman Long wrote:
>> 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@redhat.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.
> I'm looking at the mm tree (https://github.com/hnaz/linux-mm.git) and clearly
> see that commit "mm: list_lru: rename memcg_drain_all_list_lrus to
> memcg_reparent_list_lrus" eliminated the function with the name
> memcg_drain_list_lru_node(), which your patch is touching.
> Currently the function is located in list_lru.c and is named
> memcg_reparent_list_lru_node().
>
> linux-next is sometimes a bit behind the mm tree.

Oh, you are right. I will rebase the patch based on linux-mm.

Thanks for the suggestion.

Cheers,
Longman