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

[Waiman Long]

On 3/8/22 19:50, Waiman Long wrote:
> 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@xxxxxxxxxx>
> > > > 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.

The patch was originally based on the linux tree. Then I applied it onto 
linux-next without any issue. Unfortunately, I failed to notice that the 
hunk was applied to memcg_reparent_list_lru_node() without realizing 
that it is the new name for the old memcg_drain_list_lru_node(). The 
linux-next tree that I used does have all the necessary patches.

Cheers,
Longman