Re: [PATCH v9 3/9] socket: initial cgroup code.

[Glauber Costa]

On 12/23/2011 01:10 AM, Jason Baron wrote:
> On Mon, Dec 12, 2011 at 11:47:03AM +0400, Glauber Costa wrote:
> > +
> > +static bool mem_cgroup_is_root(struct mem_cgroup *memcg);
> > +void sock_update_memcg(struct sock *sk)
> > +{
> > +	/* A socket spends its whole life in the same cgroup */
> > +	if (sk->sk_cgrp) {
> > +		WARN_ON(1);
> > +		return;
> > +	}
> > +	if (static_branch(&memcg_socket_limit_enabled)) {
> > +		struct mem_cgroup *memcg;
> > +
> > +		BUG_ON(!sk->sk_prot->proto_cgroup);
> > +
> > +		rcu_read_lock();
> > +		memcg = mem_cgroup_from_task(current);
> > +		if (!mem_cgroup_is_root(memcg)) {
> > +			mem_cgroup_get(memcg);
> > +			sk->sk_cgrp = sk->sk_prot->proto_cgroup(memcg);
> > +		}
> > +		rcu_read_unlock();
> > +	}
> > +}
> > +EXPORT_SYMBOL(sock_update_memcg);
> > +
> > +void sock_release_memcg(struct sock *sk)
> > +{
> > +	if (static_branch(&memcg_socket_limit_enabled)&&  sk->sk_cgrp) {
> > +		struct mem_cgroup *memcg;
> > +		WARN_ON(!sk->sk_cgrp->memcg);
> > +		memcg = sk->sk_cgrp->memcg;
> > +		mem_cgroup_put(memcg);
> > +	}
> > +}
>
> Hi Glauber,
>
> I think for 'sock_release_memcg()', you want:
>
> static inline sock_release_memcg(sk)
> {
> 	if (static_branch())
> 		__sock_release_memcg();
> }
>
> And then re-define the current sock_release_memcg ->  __sock_release_memcg().
> In that way the straight line path is a single no-op. As currently
> written, there is function call and then an immediate return.

Hello Jason,

Thanks for the tip. I may be wrong here, but I don't think that the 
release performance matters to that level. But your suggestion seems 
good nevertheless. Since this is already sitting on a tree, would you 
like to send a patch for that?

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