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    SubjectRe: [2.4.17/18pre] VM and swap - it's really unusable
    On Wed, 9 Jan 2002 00:10:38 +0000 (GMT), Alan Cox
    <> wrote:

    >> Preemptive gives better interactivity under load, which is the whole
    >> point of multitasking (think about it). If you don't want the overhead
    >> (which also exists without preemptive) run #processes == #processors.
    >That is generally not true. Pe-emption is used in user space to prevent
    >applications doing very stupid things. Pre-emption in a trusted environment
    >can often be most efficient if done by the programs themselves.
    >Userspace is not a trusted environment
    The best part about planned preemption points is that there is minimal
    state to save when an interruption occurs.

    >> I'm really surprised that people are still actually arguing _against_
    >> preemptive multitasking in this day and age. This is a no-brainer in
    >> the long run, where current corner cases aren't holding us back.
    >Andrew's patches give you 1mS worst case latency for normal situations, that
    >is below human perception, and below scheduling granularity. In other words
    >without the efficiency loss and the debugging problems you can place the
    >far enough latency below other effects that it isnt worth attacking any more.

    Incidently human visual perception runs around 200 milliseconds
    minimum and hearing/touch perception around 100 milliseconds if the
    signal has to go through the brain. Of course we extend our
    perceptions with tools/programs etc.

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