Re: [PATCH -next v2 2/2] memcg: remove mem_cgroup_size()

[Michal Hocko]

On Wed 10-12-25 07:11:42, Chen Ridong wrote:
> From: Chen Ridong <chenridong@xxxxxxxxxx>
> 
> The mem_cgroup_size helper is used only in apply_proportional_protection
> to read the current memory usage. Its semantics are unclear and
> inconsistent with other sites, which directly call page_counter_read for
> the same purpose.
> 
> Remove this helper and replace its usage with page_counter_read for
> clarity. Additionally, rename the local variable 'cgroup_size' to 'usage'
> to better reflect its meaning.
> 
> This change is safe because page_counter_read() is only called when memcg
> is enabled in the apply_proportional_protection.
> 
> No functional changes intended.

I would prefer to keep the code as is. 

Btw.
[...]
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 670fe9fae5ba..fe48d0376e7c 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2451,6 +2451,7 @@ static inline void calculate_pressure_balance(struct scan_control *sc,
>  static unsigned long apply_proportional_protection(struct mem_cgroup *memcg,
>  		struct scan_control *sc, unsigned long scan)
>  {
> +#ifdef CONFIG_MEMCG
>  	unsigned long min, low;
>  
>  	mem_cgroup_protection(sc->target_mem_cgroup, memcg, &min, &low);
[...]
> @@ -2508,6 +2509,7 @@ static unsigned long apply_proportional_protection(struct mem_cgroup *memcg,
>  		 */
>  		scan = max(scan, SWAP_CLUSTER_MAX);
>  	}
> +#endif
>  	return scan;
>  }

This returns a random garbage for !CONFIG_MEMCG, doesn't it?

-- 
Michal Hocko
SUSE Labs