Message-ID: <491B9E8B.3080301@linux.vnet.ibm.com>
Date: Thu, 13 Nov 2008 08:57:07 +0530
From: Balbir Singh <balbir@linux.vnet.ibm.com>
Reply-To: balbir@linux.vnet.ibm.com
Organization: IBM
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To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
CC: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
       linux-kernel@vger.kernel.org, nishimura@mxp.nes.nec.co.jp,
       Paul Menage <menage@google.com>
Subject: Re: [RFC][PATCH 1/6] memcg: free all at rmdir
References: <20081112122606.76051530.kamezawa.hiroyu@jp.fujitsu.com> <20081112122656.c6e56248.kamezawa.hiroyu@jp.fujitsu.com> <20081112160758.3dca0b22.akpm@linux-foundation.org> <20081113114908.42a6a8a7.kamezawa.hiroyu@jp.fujitsu.com> <491B9BB3.6010701@linux.vnet.ibm.com> <20081113122241.b77a0d14.kamezawa.hiroyu@jp.fujitsu.com>
In-Reply-To: <20081113122241.b77a0d14.kamezawa.hiroyu@jp.fujitsu.com>
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KAMEZAWA Hiroyuki wrote:
> On Thu, 13 Nov 2008 08:44:59 +0530
> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> 
>> KAMEZAWA Hiroyuki wrote:
>>> On Wed, 12 Nov 2008 16:07:58 -0800
>>> Andrew Morton <akpm@linux-foundation.org> wrote:
>>>> If we do this then we can make the above "keep" behaviour non-optional,
>>>> and the operator gets to choose whether or not to drop the caches
>>>> before doing the rmdir.
>>>>
>>>> Plus, we get a new per-memcg drop_caches capability.  And it's a nicer
>>>> interface, and it doesn't have the obvious races which on_rmdir has,
>>>> etc.
>>>>
>>>> hm?
>>>>
>>> Balbir, how would you want to do ?
>>>
>>> I planned to post shrink_uage patch later (it's easy to be implemented) regardless
>>> of acceptance of this patch.
>>>
>>> So, I think we should add shrink_usage now and drop this is a way to go.
>> I am a bit concerned about dropping stuff at will later. Ubuntu 8.10 has memory
>> controller enabled and we exposed memory.force_empty interface there and now
>> we've dropped it (bad on our part). I think we should have deprecated it and
>> dropped it later.
>>
> I *was* documented as "for debug only".
> 

I know, but I suspect users won't. I am not blaming you in person, just trying
the find way to do such things. I think I've seen sysfs add a deprecated option
and put all deprecated files there, they are only created if someone cares about
them.

> Hmm, adding force_empty again to do "shrink usage to 0" is another choice.

Yes, sounds reasonable.

-- 
	Balbir
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