linux-kernel - Re: [PATCH 1/8] cgroup: add cgroup->id

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Message-ID: <20121120070851.GG25790@mtj.dyndns.org>
Date:	Mon, 19 Nov 2012 23:08:51 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	daniel.wagner@...-carit.de, srivatsa.bhat@...ux.vnet.ibm.com,
	john.r.fastabend@...el.com, nhorman@...driver.com,
	lizefan@...wei.com, containers@...ts.linux-foundation.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] cgroup: add cgroup->id

Hello, Kamezawa.

On Tue, Nov 20, 2012 at 04:05:51PM +0900, Kamezawa Hiroyuki wrote:
> BTW, css's ID was limited to 65535 to be encoded in 2bytes.
> If we use INT, this will increase size of swap_cgroup.
> (2bytes per page => 4bytes per page) It's preallocated at swapon()
> because allocating memory dynamically when we swap a memory is not good.
> 
> Do we really need 4bytes for ID ? If so, swap_cgroup should be totally re-designed.

That's a memcg restriction which shouldn't have been imposed on cgroup
core from the beginning.  What memcg should do is rejecting to become
online from ->css_onilne() if cgrp->id is out of the range it can
handle.

Thanks.

-- 
tejun
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