Re: [PATCH] mm, memcg: clean up reclaim iter array

[Michal Hocko <mhocko@kernel.org>]

On Mon 30-09-19 22:42:08, Yafang Shao wrote:
> The mem_cgroup_reclaim_cookie is only used in memcg softlimit reclaim now,
> and the priority of the reclaim is always 0. We don't need to define the
> iter in struct mem_cgroup_per_node as an array any more. That could make
> the code more clear and save some space.
> 
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>

Any changes to the soft limit reclaim are unlikely to happen so I tend
to agree that further simplification of the iterator is desirable.

Acked-by: Michal Hocko <mhocko@suse.com>

Thanks!

> ---
>  include/linux/memcontrol.h |  3 +--
>  mm/memcontrol.c            | 11 +++--------
>  2 files changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 0c762e8..7d99a65 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -58,7 +58,6 @@ enum mem_cgroup_protection {
>  
>  struct mem_cgroup_reclaim_cookie {
>  	pg_data_t *pgdat;
> -	int priority;
>  	unsigned int generation;
>  };
>  
> @@ -126,7 +125,7 @@ struct mem_cgroup_per_node {
>  
>  	unsigned long		lru_zone_size[MAX_NR_ZONES][NR_LRU_LISTS];
>  
> -	struct mem_cgroup_reclaim_iter	iter[DEF_PRIORITY + 1];
> +	struct mem_cgroup_reclaim_iter	iter;
>  
>  	struct memcg_shrinker_map __rcu	*shrinker_map;
>  
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 1c4c08b..5d9b00f 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1052,7 +1052,7 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
>  		struct mem_cgroup_per_node *mz;
>  
>  		mz = mem_cgroup_nodeinfo(root, reclaim->pgdat->node_id);
> -		iter = &mz->iter[reclaim->priority];
> +		iter = &mz->iter;
>  
>  		if (prev && reclaim->generation != iter->generation)
>  			goto out_unlock;
> @@ -1152,15 +1152,11 @@ static void __invalidate_reclaim_iterators(struct mem_cgroup *from,
>  	struct mem_cgroup_reclaim_iter *iter;
>  	struct mem_cgroup_per_node *mz;
>  	int nid;
> -	int i;
>  
>  	for_each_node(nid) {
>  		mz = mem_cgroup_nodeinfo(from, nid);
> -		for (i = 0; i <= DEF_PRIORITY; i++) {
> -			iter = &mz->iter[i];
> -			cmpxchg(&iter->position,
> -				dead_memcg, NULL);
> -		}
> +		iter = &mz->iter;
> +		cmpxchg(&iter->position, dead_memcg, NULL);
>  	}
>  }
>  
> @@ -1705,7 +1701,6 @@ static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg,
>  	unsigned long nr_scanned;
>  	struct mem_cgroup_reclaim_cookie reclaim = {
>  		.pgdat = pgdat,
> -		.priority = 0,
>  	};
>  
>  	excess = soft_limit_excess(root_memcg);
> -- 
> 1.8.3.1

-- 
Michal Hocko
SUSE Labs