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    SubjectRe: [rfc][patch] sched: remove smpnice
    On Wednesday 08 February 2006 01:28, Nick Piggin wrote:
    > I'd like to get some comments on removing smpnice for 2.6.16. I don't
    > think the code is quite ready, which is why I asked for Peter's additions
    > to also be merged before I acked it (although it turned out that it still
    > isn't quite ready with his additions either).
    > Basically I have had similar observations to Suresh in that it does not
    > play nicely with the rest of the balancing infrastructure (and raised
    > similar concerns in my review).
    > The samples (group of 4) I got for "maximum recorded imbalance" on a 2x2
    > SMP+HT Xeon are as follows:
    > | Following boot | hackbench 20 | hackbench 40
    > -----------+----------------+---------------------+---------------------
    > 2.6.16-rc2 | 30,37,100,112 | 5600,5530,6020,6090 | 6390,7090,8760,8470
    > +nosmpnice | 3, 2, 4, 2 | 28, 150, 294, 132 | 348, 348, 294, 347
    > Hackbench raw performance is down around 15% with smpnice (but that in
    > itself isn't a huge deal because it is just a benchmark). However, the
    > samples show that the imbalance passed into move_tasks is increased by
    > about a factor of 10-30. I think this would also go some way to
    > explaining latency blips turning up in the balancing code (though I
    > haven't actually measured that).
    > We'll probably have to revert this in the SUSE kernel.
    > The other option for 2.6.16 would be to fast track Peter's stuff, which
    > I could put some time into... but that seems a bit risky at this stage
    > of the game.
    > I'd like to hear any other suggestions though. Patch included to aid
    > discussion at this stage, rather than to encourage any rash decisions.

    I see the demonstrable imbalance but I was wondering if there is there a real
    world benchmark that is currently affected?

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