[Devel] Re: [PATCH v5 09/14] memcg: kmem accounting lifecycle management

[David Rientjes]

On Tue, 16 Oct 2012, Glauber Costa wrote:

> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 1182188..e24b388 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -344,6 +344,7 @@ struct mem_cgroup {
>  /* internal only representation about the status of kmem accounting. */
>  enum {
>  	KMEM_ACCOUNTED_ACTIVE = 0, /* accounted by this cgroup itself */
> +	KMEM_ACCOUNTED_DEAD, /* dead memcg, pending kmem charges */

"dead memcg with pending kmem charges" seems better.

>  };
>  
>  #define KMEM_ACCOUNTED_MASK (1 << KMEM_ACCOUNTED_ACTIVE)
> @@ -353,6 +354,22 @@ static void memcg_kmem_set_active(struct mem_cgroup *memcg)
>  {
>  	set_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_accounted);
>  }
> +
> +static bool memcg_kmem_is_active(struct mem_cgroup *memcg)
> +{
> +	return test_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_accounted);
> +}

I think all of these should be inline.

> +
> +static void memcg_kmem_mark_dead(struct mem_cgroup *memcg)
> +{
> +	if (test_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_accounted))
> +		set_bit(KMEM_ACCOUNTED_DEAD, &memcg->kmem_accounted);
> +}

The set_bit() doesn't happen atomically with the test_bit(), what 
synchronization is required for this?