Re: [PATCH 03/10] mm: Assign memcg-aware shrinkers bitmap to memcg

[Matthew Wilcox]

On Wed, Mar 21, 2018 at 04:21:40PM +0300, Kirill Tkhai wrote:
> +++ b/include/linux/memcontrol.h
> @@ -151,6 +151,11 @@ struct mem_cgroup_thresholds {
>  	struct mem_cgroup_threshold_ary *spare;
>  };
>  
> +struct shrinkers_map {
> +	struct rcu_head rcu;
> +	unsigned long *map[0];
> +};
> +
>  enum memcg_kmem_state {
>  	KMEM_NONE,
>  	KMEM_ALLOCATED,
> @@ -182,6 +187,9 @@ struct mem_cgroup {
>  	unsigned long low;
>  	unsigned long high;
>  
> +	/* Bitmap of shrinker ids suitable to call for this memcg */
> +	struct shrinkers_map __rcu *shrinkers_map;
> +
>  	/* Range enforcement for interrupt charges */
>  	struct work_struct high_work;
>  

Why use your own bitmap here?  Why not use an IDA which can grow and
shrink automatically without you needing to play fun games with RCU?