* [PATCH] mm/list_lru: Optimize memcg_drain_list_lru_node()
@ 2022-03-08 3:30 Waiman Long
2022-03-08 4:39 ` Roman Gushchin
0 siblings, 1 reply; 6+ messages in thread
From: Waiman Long @ 2022-03-08 3:30 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-mm, linux-kernel, Muchun Song, Waiman Long
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>
---
mm/list_lru.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/mm/list_lru.c b/mm/list_lru.c
index 0cd5e89ca063..100ca453e885 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -518,6 +518,12 @@ static void memcg_drain_list_lru_node(struct list_lru *lru, int nid,
int dst_idx = dst_memcg->kmemcg_id;
struct list_lru_one *src, *dst;
+ /*
+ * If there is no lru entry in this nlru, we can skip it immediately.
+ */
+ if (!READ_ONCE(nlru->nr_items))
+ return;
+
/*
* Since list_lru_{add,del} may be called under an IRQ-safe lock,
* we have to use IRQ-safe primitives here to avoid deadlock.
--
2.27.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] mm/list_lru: Optimize memcg_drain_list_lru_node()
2022-03-08 3:30 [PATCH] mm/list_lru: Optimize memcg_drain_list_lru_node() Waiman Long
@ 2022-03-08 4:39 ` Roman Gushchin
2022-03-08 15:41 ` Waiman Long
0 siblings, 1 reply; 6+ messages in thread
From: Roman Gushchin @ 2022-03-08 4:39 UTC (permalink / raw)
To: Waiman Long; +Cc: Andrew Morton, linux-mm, linux-kernel, Muchun Song
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!
> ---
> mm/list_lru.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/mm/list_lru.c b/mm/list_lru.c
> index 0cd5e89ca063..100ca453e885 100644
> --- a/mm/list_lru.c
> +++ b/mm/list_lru.c
> @@ -518,6 +518,12 @@ static void memcg_drain_list_lru_node(struct list_lru *lru, int nid,
> int dst_idx = dst_memcg->kmemcg_id;
> struct list_lru_one *src, *dst;
>
> + /*
> + * If there is no lru entry in this nlru, we can skip it immediately.
> + */
> + if (!READ_ONCE(nlru->nr_items))
> + return;
> +
> /*
> * Since list_lru_{add,del} may be called under an IRQ-safe lock,
> * we have to use IRQ-safe primitives here to avoid deadlock.
> --
> 2.27.0
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/list_lru: Optimize memcg_drain_list_lru_node()
2022-03-08 4:39 ` Roman Gushchin
@ 2022-03-08 15:41 ` Waiman Long
2022-03-09 0:17 ` Roman Gushchin
0 siblings, 1 reply; 6+ messages in thread
From: Waiman Long @ 2022-03-08 15:41 UTC (permalink / raw)
To: Roman Gushchin; +Cc: Andrew Morton, linux-mm, linux-kernel, Muchun Song
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.
Cheers,
Longman
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/list_lru: Optimize memcg_drain_list_lru_node()
2022-03-08 15:41 ` Waiman Long
@ 2022-03-09 0:17 ` Roman Gushchin
2022-03-09 0:50 ` Waiman Long
0 siblings, 1 reply; 6+ messages in thread
From: Roman Gushchin @ 2022-03-09 0:17 UTC (permalink / raw)
To: Waiman Long; +Cc: Andrew Morton, linux-mm, linux-kernel, Muchun Song
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.
Thanks!
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/list_lru: Optimize memcg_drain_list_lru_node()
2022-03-09 0:17 ` Roman Gushchin
@ 2022-03-09 0:50 ` Waiman Long
2022-03-09 1:06 ` Waiman Long
0 siblings, 1 reply; 6+ messages in thread
From: Waiman Long @ 2022-03-09 0:50 UTC (permalink / raw)
To: Roman Gushchin; +Cc: Andrew Morton, linux-mm, linux-kernel, Muchun Song
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
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/list_lru: Optimize memcg_drain_list_lru_node()
2022-03-09 0:50 ` Waiman Long
@ 2022-03-09 1:06 ` Waiman Long
0 siblings, 0 replies; 6+ messages in thread
From: Waiman Long @ 2022-03-09 1:06 UTC (permalink / raw)
To: Roman Gushchin; +Cc: Andrew Morton, linux-mm, linux-kernel, Muchun Song
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@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.
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
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-03-09 1:16 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-03-08 3:30 [PATCH] mm/list_lru: Optimize memcg_drain_list_lru_node() Waiman Long
2022-03-08 4:39 ` Roman Gushchin
2022-03-08 15:41 ` Waiman Long
2022-03-09 0:17 ` Roman Gushchin
2022-03-09 0:50 ` Waiman Long
2022-03-09 1:06 ` Waiman Long
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.