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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 <balbir@linux.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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