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Message-ID: <47DDE187.70109@linux.vnet.ibm.com>
Date: Mon, 17 Mar 2008 08:42:07 +0530
From: Balbir Singh <balbir@...ux.vnet.ibm.com>
To: Paul Menage <menage@...gle.com>
CC: linux-mm@...ck.org, Hugh Dickins <hugh@...itas.com>,
Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
YAMAMOTO Takashi <yamamoto@...inux.co.jp>, lizf@...fujitsu.com,
linux-kernel@...r.kernel.org, taka@...inux.co.jp,
David Rientjes <rientjes@...gle.com>,
Pavel Emelianov <xemul@...nvz.org>,
Andrew Morton <akpm@...ux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [RFC][0/3] Virtual address space control for cgroups
Paul Menage wrote:
> On Mon, Mar 17, 2008 at 9:50 AM, Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
>> I am yet to measure the performance overhead of the accounting checks. I'll try
>> and get started on that today. I did not consider making it a separate system,
>> because I suspect that anybody wanting memory control would also want address
>> space control (for the advantages listed in the documentation).
>
> I'm a counter-example to your suspicion :-)
>
> Trying to control virtual address space is a complete nightmare in the
> presence of anything that uses large sparsely-populated mappings
> (mmaps of large files, or large sparse heaps such as the JVM uses.)
>
Not really. Virtual limits are more gentle than an OOM kill that can occur if
the cgroup runs out of memory. Please also see
http://linux-vserver.org/Memory_Limits
> If we want to control the effect of swapping, the right way to do it
> is to control disk I/O, and ensure that the swapping is accounted to
> that. Or simply just not give apps much swap space.
Yes, a disk I/O and swap I/O controller are being developed (not by us, but
others in the community). How does one restrict swap space for a particular
application? I can think of RLIMIT_AS for a process and something similar to
what I've posted for cgroups. Not enabling swap is an option, but not very
practical IMHO.
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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