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SubjectRe: [RFC][0/3] Virtual address space control for cgroups
Paul Menage wrote:
> On Mon, Mar 17, 2008 at 9:50 AM, Balbir Singh <> 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

> 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

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