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    SubjectRe: [patch] sched: fix broken smt/mc optimizations with CFS
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    On Thu, 2007-08-23 at 14:13 +0200, Ingo Molnar wrote:
    > * Ingo Molnar <mingo@elte.hu> wrote:
    >
    > > [...] So how about the patch below instead?
    >
    > the right patch attached.
    >
    > -------------------------------->
    > Subject: sched: fix broken SMT/MC optimizations
    > From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
    >
    > On a four package system with HT - HT load balancing optimizations were
    > broken. For example, if two tasks end up running on two logical threads
    > of one of the packages, scheduler is not able to pull one of the tasks
    > to a completely idle package.
    >
    > In this scenario, for nice-0 tasks, imbalance calculated by scheduler
    > will be 512 and find_busiest_queue() will return 0 (as each cpu's load
    > is 1024 > imbalance and has only one task running).

    Is there an upper bound on the number of tasks that can migrate during a
    new idle balance? The reason that I'm asking is because I've been seeing
    some large latency in the new idle path into load_balance().. I'm not
    sure if lots of tasks are getting migrated or if it's just the iteration
    over tasks in the rb-tree ..

    Daniel

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