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    Date
    SubjectRe: High contention on the sk_buff_head.lock
    From
    From: Vernon Mauery <vernux@us.ibm.com>
    Date: Wed, 18 Mar 2009 14:10:33 -0700

    > David Miller wrote:
    > > From: Andi Kleen <andi@firstfloor.org>
    > > Date: Wed, 18 Mar 2009 21:54:37 +0100
    > >
    > >> But then again I'm not sure it's worth it if the problem only
    > >> happens in out of tree RT.
    > > The list of problems that only show up with the RT kernel seems to be
    > > constantly increasing, but honestly is very surprising to me.
    > > I don't understand why we even need to be concerned about this stuff
    > > upstream, to be honest.
    > > Please reproduce this in the vanilla kernel, then get back to us.
    >
    > Huh? The numbers that I posted *were* from the vanilla kernel. I ran
    > the 2.6.29-rc8 kernel with lock_stat enabled. The lock contention
    > happens on the same lock in both vanilla and -rt, it just happens
    > to be more pronounced in the -rt kernel because of the double context
    > switches that the sleeping spinlock/rt-mutexes introduce.

    And the double context switches are probably also why less
    natural batching and locality are achieved in the RT kernel.

    Isn't that true?


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