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    SubjectRe: [PATCH -mm] change anon_vma linking to fix multi-process server scalability issue
    On 02/11/2010 04:04 PM, Andrew Morton wrote:
    > On Thu, 28 Jan 2010 00:20:00 -0500
    > Rik van Riel<riel@redhat.com> wrote:
    >
    >> The old anon_vma code can lead to scalability issues with heavily
    >> forking workloads. Specifically, each anon_vma will be shared
    >> between the parent process and all its child processes.

    Some test results:

    Without the anon_vma changes, when AIM7 hits around 9.7k
    users (on a test box with 16GB RAM and not quite enough IO),
    the system ends up running >99% in system time, with every
    CPU on the same anon_vma lock in the pageout code.

    With these changes, AIM7 hits the cross-over point around
    29.7k users. This happens with ~99% IO wait time, there
    never seems to be any spike in system time. The anon_vma
    lock contention appears to be resolved.

    --
    All rights reversed.


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