linux-kernel - Re: [PATCH 1/6] res_counter: handle limit change

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Message-ID: <48562894.5080307@openvz.org>
Date:	Mon, 16 Jun 2008 12:47:16 +0400
From:	Pavel Emelyanov <xemul@...nvz.org>
To:	kamezawa.hiroyu@...fujitsu.com
CC:	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	menage@...gle.com, balbir@...ux.vnet.ibm.com,
	yamamoto@...inux.co.jp, nishimura@....nes.nec.co.jp,
	lizf@...fujitsu.com
Subject: Re: [PATCH 1/6] res_counter:  handle limit change

kamezawa.hiroyu@...fujitsu.com wrote:
> ----- Original Message -----
> 
>> kamezawa.hiroyu@...fujitsu.com wrote:
>>> ----- Original Message -----
>>>
>>>>> I think when I did all in memcg, someone will comment that "why do that
>>>>> all in memcg ? please implement generic one to avoid code duplication"
>>>> Hm... But we're choosing between
>>>>
>>>> sys_write->xxx_cgroup_write->res_counter_set_limit->xxx_cgroup_call
>>>>
>>>> and
>>>>
>>>> sys_write->xxx_cgroup_write->res_counter_set_limit
>>>>                           ->xxx_cgroup_call
>>>>
>>>> With the sizeof(void *)-bytes difference in res_counter, nNo?
>>>>
>>> I can't catch what you mean. What is res_counter_set_limit here ?
>> It's res_counter_resize_limit from your patch, sorry for the confusion.
>>
>>> (my patche's ?) and what is sizeof(void *)-bytes ?
>> I meant, that we have to add 4 bytes (8 on 64-bit arches) on the
>> struct res_counter to store the pointer on the res_counter_ops.
>>
> Okay, maye all you want is "don't increase the size of res_counter"

Actually no, what I want is not to put indirections level when
not required.

But keeping res_counter as small as possible is also my wish. :)

>>> Is it so strange to add following algorithm in res_counter?
>>> ==
>>> set_limit -> fail -> shrink -> set limit -> fail ->shrink
>>> -> success -> return 0
>>> ==
>>> I think this is enough generic.
>> It is, but my point is - we're calling the set_limit (this is a
>> res_counter_resize_limit from your patch, sorry for the confusion again)
>> routine right from the cgroup's write callback and thus can call
>> the desired "ops->shrink_usage" directly, w/o additional level of
>> indirection.
>>
> Hmm, to do that, I'd like to remove strategy function from res_counter.

Oops... I'm looking at 2.6.26-rc5-mm1's res_counter and don't see such.
I tried to follow the changes in res_counter, but it looks like I've
already missed something. 

What do you mean by "strategy function from res_counter"?

> Ok? 
> 
> Thanks,
> -Kame
> 

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