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

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Date:	Mon, 16 Jun 2008 12:23:55 +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 -----
> 
>>> 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.

> 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.

> Thanks,
> -Kame
> 
> 
> 
> 

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