[Devel] [PATCH 7/7] packet: Pre-account maximum socket buffer into cg memory (v2)

[Pavel Emelyanov]

On 06/04/2015 01:53 PM, Vladimir Davydov wrote:
> On Thu, Jun 04, 2015 at 12:47:47PM +0300, Pavel Emelyanov wrote:
>> On 06/04/2015 12:02 PM, Vladimir Davydov wrote:
>>> On Wed, Jun 03, 2015 at 04:35:35PM +0300, Pavel Emelyanov wrote:
>>>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>>>> index 4d0a756..45bc78d 100644
>>>> --- a/mm/memcontrol.c
>>>> +++ b/mm/memcontrol.c
>>>> @@ -534,6 +534,20 @@ void sock_update_memcg(struct sock *sk)
>>>>  }
>>>>  EXPORT_SYMBOL(sock_update_memcg);
>>>>  
>>>> +struct mem_cgroup *try_get_mem_cgroup_from_current(void)
>>>> +{
>>>> +	struct mem_cgroup *cg;
>>>> +
>>>> +	rcu_read_lock();
>>>> +	cg = mem_cgroup_from_task(current);
>>>> +	if (mem_cgroup_is_root(cg) || !css_tryget(&cg->css))
>>>> +		cg = NULL;
>>>> +	rcu_read_unlock();
>>>> +
>>>> +	return cg;
>>>> +}
>>>> +EXPORT_SYMBOL(try_get_mem_cgroup_from_current);
>>>> +
>>>
>>> Why not use try_get_mem_cgroup_from_mm(current->mm) instead?
>>
>> Because it's stupid, I don't need the steps it does when trying 
>> to pick the mm owner in a loop.
> 
> Our goal is to reduce churn.

Really?!

> In particular, this means reusing existing functions wherever possible.

Even "reducing churn" goal doesn't mean so.

> This particular function does what you need
> and there is no point to care if it is stupid or not, just use it :-)
> The caller of this function is not in a hot path anyway.

Nice concept. Why not remove ve_struct->_venet_dev then? We can always safely
do the __dev_get_by_name(ve->ve_ns->net_ns, "venet0").

-- Pavel