On 12/23/2011 01:10 AM, Jason Baron wrote:

On Mon, Dec 12, 2011 at 11:47:03AM +0400, Glauber Costa wrote:

quoted

+
+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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