2021-04-13 09:11:48

by Muchun Song

Subject: [PATCH 6/7] mm: memcontrol: move obj_cgroup_uncharge_pages() out of css_set_lock

The css_set_lock is used to guard the list of inherited objcgs. So there
is no need to uncharge kernel memory under css_set_lock. Just move it
out of the lock.

Signed-off-by: Muchun Song <[email protected]>
---
mm/memcontrol.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 42d8c0f4ab1d..d9c7e44abcd0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -289,9 +289,10 @@ static void obj_cgroup_release(struct percpu_ref *ref)
WARN_ON_ONCE(nr_bytes & (PAGE_SIZE - 1));
nr_pages = nr_bytes >> PAGE_SHIFT;

- spin_lock_irqsave(&css_set_lock, flags);
if (nr_pages)
obj_cgroup_uncharge_pages(objcg, nr_pages);
+
+ spin_lock_irqsave(&css_set_lock, flags);
list_del(&objcg->list);
spin_unlock_irqrestore(&css_set_lock, flags);

--
2.11.0

2021-04-13 20:11:08

by Shakeel Butt

Subject: Re: [PATCH 6/7] mm: memcontrol: move obj_cgroup_uncharge_pages() out of css_set_lock

On Mon, Apr 12, 2021 at 11:58 PM Muchun Song <[email protected]> wrote:
>
> The css_set_lock is used to guard the list of inherited objcgs. So there
> is no need to uncharge kernel memory under css_set_lock. Just move it
> out of the lock.
>
> Signed-off-by: Muchun Song <[email protected]>

Reviewed-by: Shakeel Butt <[email protected]>

2021-04-14 04:42:23

by Johannes Weiner

Subject: Re: [PATCH 6/7] mm: memcontrol: move obj_cgroup_uncharge_pages() out of css_set_lock

On Tue, Apr 13, 2021 at 02:51:52PM +0800, Muchun Song wrote:
> The css_set_lock is used to guard the list of inherited objcgs. So there
> is no need to uncharge kernel memory under css_set_lock. Just move it
> out of the lock.
>
> Signed-off-by: Muchun Song <[email protected]>

Acked-by: Johannes Weiner <[email protected]>

2021-04-14 05:23:17

by Roman Gushchin

Subject: Re: [PATCH 6/7] mm: memcontrol: move obj_cgroup_uncharge_pages() out of css_set_lock

On Tue, Apr 13, 2021 at 02:51:52PM +0800, Muchun Song wrote:
> The css_set_lock is used to guard the list of inherited objcgs. So there
> is no need to uncharge kernel memory under css_set_lock. Just move it
> out of the lock.
>
> Signed-off-by: Muchun Song <[email protected]>

Acked-by: Roman Gushchin <[email protected]>

> ---
> mm/memcontrol.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 42d8c0f4ab1d..d9c7e44abcd0 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -289,9 +289,10 @@ static void obj_cgroup_release(struct percpu_ref *ref)
> WARN_ON_ONCE(nr_bytes & (PAGE_SIZE - 1));
> nr_pages = nr_bytes >> PAGE_SHIFT;
>
> - spin_lock_irqsave(&css_set_lock, flags);
> if (nr_pages)
> obj_cgroup_uncharge_pages(objcg, nr_pages);
> +
> + spin_lock_irqsave(&css_set_lock, flags);
> list_del(&objcg->list);
> spin_unlock_irqrestore(&css_set_lock, flags);
>
> --
> 2.11.0
>