[Devel] Re: [PATCH 4/4] get rid of populate for memcg

[Tejun Heo]

Hello, Glauber.

On Tue, Mar 20, 2012 at 08:50:56PM +0400, Glauber Costa wrote:
> @@ -4929,7 +4929,9 @@ mem_cgroup_create(struct cgroup *cont)
>  	atomic_set(&memcg->refcnt, 1);
>  	memcg->move_charge_at_immigrate = 0;
>  	mutex_init(&memcg->thresholds_lock);
> -	return &memcg->css;
> +
> +	if (!register_kmem_files(memcg, &mem_cgroup_subsys))
> +		return &memcg->css;

After the change, I think register_kmem_files() is a quite misleading
name.

> @@ -2484,6 +2484,11 @@ int proto_register(struct proto *prot, int alloc_slab)
>  		}
>  	}
>  
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> +	if (prot->init_cgroup)
> +		prot->init_cgroup(NULL, NULL);
> +#endif

So, init_cgroup() is overloaded to do two things - one load time init
and per-cgroup init, depending on the args.

> @@ -37,7 +37,6 @@ static struct cftype tcp_files[] = {
>  	},
>  	{ }	/* terminate */
>  };
> -CGROUP_SUBSYS_CFTYPES(mem_cgroup_subsys, tcp_files);

What I don't get is why you can't just keep this.  Is it because the
files might appear before the protocol is registered?  Wouldn't it be
much better to add ipv4_tcp_init_cgroup() or whatever call to
inet_init() instead of overloading init_cgroup() with mostly unrelated
stuff?

Thanks.

-- 
tejun