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    SubjectRe: Linux 2.4.19-rc3 (hyperthreading)
    Date
    On Monday 29 July 2002 4:28 pm, Alan Cox wrote:
    > On Mon, 2002-07-29 at 20:54, Andrew Theurer wrote:
    > > I would caution against having hyperthreading on by default in the 2.4.19
    > > release. I am seeing a significant degrade in network workloads on P4
    > > with hyperthreading on. On 2.4.19-pre10, I get 788 Mbps on NetBench, but
    > > on 2.4.19-rc1 (and probably rc3, should know in an hour), I get 690 Mbps.
    > > It is clearly a hyperthreading/interrupt routing issue. On this system
    > > (4 x P4),
    >
    > Quite possibly. I've just merged the O(1) scheduler load balancing fixes
    > for the hyperthreading stuff, rc3 uses the old scheduler so that isnt
    > your problem. For most workloads I see a speed up. The more cache
    > optimised the workload the less the speedup.
    >
    > Its quite possible the irq routing ought to be smarter, at the moment
    > I'm not sure of the best approaches.

    Agreed, we need some sort of irqbalance, and I intend to test with Ingo's and
    Andrea's approaches. With that addition, I may even see an improvement with
    hyperthreading. But for an rc release, I think it would be prudent to revert
    the "new code" for default hyperthreading behavior, and attack the whole
    problem in 2.4.20 or later release.

    -Andrew Theurer

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