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    SubjectRe: [PATCH v1] sched: steer waking task to empty cfs_rq for better latencies
    * Peter Zijlstra <> [2012-04-24 19:09:14]:

    > On Tue, 2012-04-24 at 18:58 +0200, Peter Zijlstra wrote:
    > > On Tue, 2012-04-24 at 22:26 +0530, Srivatsa Vaddagiri wrote:
    > > > Steer a waking task towards a cpu where its cgroup has zero tasks (in
    > > > order to provide it better sleeper credits and hence reduce its wakeup
    > > > latency).
    > >
    > > That's just vile.. pjt could you post your global vruntime stuff so
    > > vatsa can have a go at that?
    > That is, you're playing a deficiency we should fix, not exploit.
    > Also, you do a second loop over all those cpus right after we've already
    > iterated them..

    The first loop doesn't necessarily iterate thr' all cpus (as its looking
    for a core that is fully idle - and hence breaks once it finds a busy

    > furthermore, that 100%+ gain is still way insane, what else is broken?


    I have tried most benchmarks that were recommended for this kind of
    change. Let me know if you suggest any other benchmark ..

    > Did you try those paravirt tlb-flush patches and other such weirdness?

    I will try that next. But IMHO the benefit of reduced wakeup latencies
    should be over and above any benefit we get from paravirtualization.

    - vatsa

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