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    SubjectRe: [RFC] scheduler: improve SMP fairness in CFS

    * Tong Li <> wrote:

    > > you need to measure it over longer periods of time. Its not worth
    > > balancing for such a thing in any high-frequency manner. (we'd trash
    > > the cache constantly migrating tasks back and forth.)
    > I have some data below, but before that, I'd like to say, at the same
    > load balancing rate, my proposed approach would allow us to have
    > fairness on the order of seconds. I'm less concerned about trashing
    > the cache. The important thing is to have a knob that allow users to
    > trade off fairness and performance based on their needs. [...]

    such a knob already exists to a certain degree, but i havent tested its
    full effects on SMP fairness yet. If you pull my scheduler tree:


    and if you enable CONFIG_SCHED_DEBUG, then all the sched-domain
    parameters become runtime tunable under /proc/sys/cpu*.

    Could you try to increase the cross-CPU rebalancing frequency and see
    how it impacts the precision of your measurement? Tune 'min_interval'
    and 'max_interval' down to increase the frequency of rebalancing.

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      Last update: 2007-07-26 23:35    [W:0.020 / U:1.268 seconds]
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