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    SubjectRe: new IRQ scalability changes in 2.3.48

    On Mon, 13 Mar 2000, Linus Torvalds wrote:

    > We want to avoid having long latencies, and we can easily get that by
    > just allowing timer interrupts to schedule which we're in a big
    > "memcpy_to_user()" and we don't hold any kernel lock etc. No need to
    > try to be clever at lock release time - if we get a pending
    > reschedule, we might as well leave it pending, it's going to be
    > serviced soon enough anyway.

    yep - and the 'natural blocking' of memcpys is bound (in size) anyway, so
    the conditional reschedule is probably faster (and an already proven
    solution). I believe there is one more reason to allow a memcpy to finish
    before rescheduling: the source buffer is often (especially in the
    networking case) already cached, so we are better off if we wait 100 usecs
    and reschedule _after_ the memcpy.


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