linux-kernel - Re: Re: [PATCH 2/2] memcg: reduce usage at change limit

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Date:	Fri, 20 Jun 2008 15:44:41 +0900 (JST)
From:	kamezawa.hiroyu@...fujitsu.com
To:	Paul Menage <menage@...gle.com>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	balbir@...ux.vnet.ibm.com, xemul@...nvz.org, lizf@...fujitsu.com,
	yamamoto@...inux.co.jp, nishimura@....nes.nec.co.jp,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Re: [PATCH 2/2] memcg: reduce usage at change limit

----- Original Message -----
>Date: 	Thu, 19 Jun 2008 22:16:07 -0700
>From: "Paul Menage" <menage@...gle.com>
>> Reduce the usage of res_counter at the change of limit.
>>
>> Changelog v4 -> v5.
>>  - moved "feedback" alogrithm from res_counter to memcg.
>
>FWIW, I really thought it was much better having it in the generic res_counte
r.
>
Hmm ;)

Balbir and Pavel pointed out that

the resouce which can shrink if necessary is
 - user's memory usage
 - kernel memory (slab) if it can. (not implemented)

And there are other users of res_counter which cannot shrink.
(I think -EBUSY should be returned)

Now, my idea is
- implement "feedback" in memcg because it is an only user
- fix res_counter to return -EBUSY

I think we can revisit later "implement generic feedback in res_counter".
And such kind of implementation change will not big.(I think)

Another point is I don't want to make res_counter big. To support
generic ops in res_counter (handle limit, hierarchy, high-low watermark...)
res_counter must be bigger that it is. And most of users of res_counder doesn'
t want such ops.

To be honest, both way is okay to me. But I'd like to start from not-invasive
one.

Thanks,
-Kame

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