linux-kernel - Re: RFC [Patch] Remove "please try 'cgroup_disable=memory' option if you don't want memory cgroups" printk at boot time.

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Message-Id: <20100401104859.e0deeca8.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 1 Apr 2010 10:48:59 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	Larry Woodman <lwoodman@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"kamezawa.hiroyu@...fujitsu.com" <kamezawa.hiroyu@...fujitsu.com>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: RFC [Patch] Remove
 "please try 'cgroup_disable=memory' option if you don't want memory cgroups"
 printk at boot time.

On Wed, 31 Mar 2010 13:57:46 -0400
Rik van Riel <riel@...hat.com> wrote:

> On 03/31/2010 11:54 AM, Larry Woodman wrote:
> > On Wed, 2010-03-31 at 11:28 -0400, Larry Woodman wrote:
> >> We are considering removing this printk at boot time from RHEL because
> >> it will confuse customers, encourage them to change the boot parameters
> >> and generate extraneous support calls.  Its documented in
> >> Documentation/kernel-parameters.txt anyway.  Any thoughts???
> 
> Yeah, that is a strange boot message...
> 
> Acked-by: Rik van Riel <riel@...hat.com>
> 
please CC linux-mm and maintainers.

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

It have been there for a year and I think memory usage by page_cgroup
will not surprise linux kernel users, more.

Assume x86-32.

RHEL allows amount of memory up to 16G, right?

without memcg: memmap uses 32bytes * 16G/4k = 128M.
with memcg:    memmap+page_cgroup uses (32+20) bytes * 16G/4k = 208M.

I thought this may cause OOM in ZONE_NORMAL. Then, I added it when I wrote
original patch. This kind of memory eater can cause trouble when it pops
up suddenly. But I think 'one year' can be an excuse.

Thanks,
-Kame


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