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    SubjectRe: big picture UDP/IP performance question re 2.6.18 -> 2.6.32
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    Le samedi 01 octobre 2011 à 14:16 -0400, starlight@binnacle.cx a écrit :
    > At 08:44 AM 10/1/2011 +0200, Eric Dumazet wrote:
    > >In my experience, I have the exact opposite :
    > >performance greatly improved in recent
    > >kernels. Unless you compile your kernel to include
    > >new features that might reduce performance
    > >(namespaces, cgroup, ...)
    >
    > RH has both of the above turned on in the
    > 2.6.32-71.29.1.el6.x86_64 kernel tested.
    >
    > If these are big negatives to network
    > performance, could you list what should
    > specifically turned off to maximize
    > results? Also a recommendation for
    > the best recent kernel for another
    > benchmark would be helpful.
    >
    > Probably can't convince anyone to deploy a
    > kernel without commercial support, but if
    > an alternate compile fixes performance it
    > might be possible to convince RH to support
    > the alternative build.
    >

    2.6.32 has a perf tool, that can really help to spot in a few minutes
    hot spots. That would definitely help to further diagnose what could be
    the problem in your workload.

    A single patch can have huge performance impact, sometime not noticed.

    For example, in 2.6.36, AF_UNIX support for pid namespaces dropped
    performance a lot [commit 7361c36c5224 (af_unix: Allow credentials to
    work across user and pid namespaces)], because of a single atomic
    operation, but done on each send() and receive() on a central location.



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