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    SubjectRe: [RFC PATCHSET] workqueue: implement concurrency managed workqueue
    On 10/01/2009 10:40 AM, Ingo Molnar wrote:
    > Ok, this looks fairly interesting - and the way you reused scheduler
    > classes to auto-regulate with no impact on regular performance is quite
    > an ingenious idea as well. (KVM's preempt notifiers should probably use
    > this trick too, instead of an ugly notifier in the scheduler hotpath)
    >
    > This mechanism could be used to implement threadlets/syslets too btw.,
    > and other forms of asynchronous IO.
    >

    In fact I've thought of implementing threadlets and concurrency-managed
    workqueues with preempt notifiers ;)

    Isn't a scheduling class overkill for two existing callbacks? Note we
    can easily use a thread flag and __switch_to_xtra() to avoid the overhead.

    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.

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



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