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    SubjectRe: [RFC PATCHSET] workqueue: implement concurrency managed workqueue
    On 10/01/2009 06:55 PM, Tejun Heo wrote:
    >> For kvm, we don't want to force a specific scheduling class for vcpu
    >> threads, so we'd need infrastructure to create a new scheduling class
    >> out of an existing one to hook the two callbacks. Seems like quite a
    >> lot of work, for something that is orthogonal to scheduling.
    >>
    >> Tejun, would preempt notifiers work for your workqueues? see bottom of
    >> include/linux/preempt.h.
    >>
    > I considered that but the thing is workqueue needs to know when a
    > thread wakes up not when it gets scheduled. Of course we can add
    > another notifier op and call it from try_to_wake_up() but I really
    > didn't want to add yet another hook in a very hot path which will only
    > be useful for very small number of tasks but yet has to be called for
    > every operation and the sched_class mechanism means that we already
    > have hooks at all the interesting spots, so I think it's better to
    > make use of them instead of adding another set of callbacks.
    >

    Right, it's a subtle difference that makes p_n unusable for you.

    --
    Do not meddle in the internals of kernels, for they are subtle and quick to panic.



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