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

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Message-ID: <4EF4428D.6010103@parallels.com>
Date:	Fri, 23 Dec 2011 12:57:49 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Jason Baron <jbaron@...hat.com>
CC:	<davem@...emloft.net>, <linux-kernel@...r.kernel.org>,
	<paul@...lmenage.org>, <lizf@...fujitsu.com>,
	<kamezawa.hiroyu@...fujitsu.com>, <ebiederm@...ssion.com>,
	<gthelen@...gle.com>, <netdev@...r.kernel.org>,
	<linux-mm@...ck.org>, <kirill@...temov.name>,
	<avagin@...allels.com>, <devel@...nvz.org>,
	<eric.dumazet@...il.com>, <cgroups@...r.kernel.org>
Subject: Re: [PATCH v9 3/9] socket: initial cgroup code.

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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