netdev - Re: [BUGFIX][PATCH 3/3] memcg/tcp: ignore tcp usage before accounting started

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Date:	Sun, 8 Apr 2012 22:44:46 -0300
From:	Glauber Costa <glommer@...allels.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	David Miller <davem@...emloft.net>, <netdev@...r.kernel.org>,
	<akpm@...ux-foundation.org>
Subject: Re: [BUGFIX][PATCH 3/3] memcg/tcp: ignore tcp usage before accounting
 started

On 04/08/2012 09:58 PM, KAMEZAWA Hiroyuki wrote:
> (2012/04/04 7:31), Glauber Costa wrote:
>
>> On 04/02/2012 07:41 AM, David Miller wrote:
>>> From: Glauber Costa<glommer@...allels.com>
>>> Date: Thu, 29 Mar 2012 11:21:07 +0200
>>>
>>>> On 03/29/2012 09:10 AM, KAMEZAWA Hiroyuki wrote:
>>>>> tcp memcontrol starts accouting after res->limit is set. So, if a sockets
>>>>> starts before setting res->limit, there are already used resource.
>>>>> After setting res->limit, the resource (already used) will be uncharged and
>>>>> make res_counter below 0 because they are not charged. This causes warning.
>>>>>
>>>>> This patch fixes that by adding res_counter_uncharge_nowarn().
>>>>> (*) We cannot avoid this while we have 'account start' switch.
>>>>>
>>>>> Signed-off-by: KAMEZAWA Hiroyuki<kamezawa.hiroyu@...fujitsu.com>
>>>>
>>>> Fine by me.
>>>>
>>>> Acked-by: Glauber Costa<glommer@...allels.com>
>>>
>>> I'm not applying patches that simply ignore accounting counter
>>> underflows.
>>>
>>> You must either:
>>>
>>> 1) Integrate the socket's existing usage when the limit is set.
>>>
>>> 2) Avoid accounting completely for a socket that started before
>>>      the limit was set.
>>>
>>> No half-way solutions, please.  Otherwise it is impossible to design
>>> validations of the resource usage for a particular socket or group of
>>> sockets, because they can always be potentially "wrong" and over the
>>> limit.  That's a design for a buggy system.
>>>
>>>
>> Kame,
>>
>> I agree with Dave FWIW.
>>
>> We should be able to do this by dropping the reference count when the
>> cgroup is finally destroyed, instead of from the remove callback. At
>> that point, no more pending sockets should be attached to it.
>>
>> Prior to increasing the static key, they are all assigned to the global
>> cgroup, so we shouldn't care about them.
>>
>
> Could you do the fix ?
>
> Thanks,
> -Kame
>
>
I sent you a version already. Please just make sure it works for you

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