Re: [PATCH v1 7/9] mm: memcg: guard memcg1-specific members of struct mem_cgroup_per_node

Shakeel Butt
2024-06-29T00:52:42Z

On Fri, Jun 28, 2024 at 09:03:15PM GMT, Roman Gushchin wrote:
> Put memcg1-specific members of struct mem_cgroup_per_node under the
> CONFIG_MEMCG_V1 config option.
>
> Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
> ---
> include/linux/memcontrol.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 107b0c5d6eab..c7ef628ee882 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -92,6 +92,7 @@ struct mem_cgroup_per_node {
> struct lruvec_stats *lruvec_stats;
> struct shrinker_info __rcu *shrinker_info;
>
> +#ifdef CONFIG_MEMCG_V1
> /*
> * Memcg-v1 only stuff in middle as buffer between read mostly fields
> * and update often fields to avoid false sharing. Once v1 stuff is
> @@ -102,6 +103,7 @@ struct mem_cgroup_per_node {
> unsigned long usage_in_excess;/* Set to the value by which */
> /* the soft limit is exceeded*/
> bool on_tree;

Here we definitely need a padding after the pointers and before the
lruvec. We can add a #else to the #ifdef CONFIG_MEMCG_V1 and put a
cacheline padding in it.

> +#endif
>
> /* Fields which get updated often at the end. */
> struct lruvec lruvec;
> --
> 2.45.2.803.g4e1b14247a-goog
>