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    SubjectRe: [rtl] Low-latency patches working GREAT (<2.9ms audio latency), see testresults ,but ISDN troubles
    On Sun, Aug 29, 1999 at 09:15:19AM +0200, Ingo Molnar wrote:
    > On Sat, 28 Aug 1999 wrote:
    > > I'm concerned that the major improvement has come from additional
    > > calls to schedule instead of from some basic improvements in algorithm.
    > there are _no_ extra calls to schedule, only if necessery. Zero, nil,
    > nada. Please check out the patch.

    Tell me what I misunderstood. As far as I can tell, pre patch behavior
    involves many fewer calls to schedule, post patch behavior for a write, for
    example, can make at least one extra call to the scheduler for every block
    copied. If "needs_resched >0" it is still not necessarily true that the
    call to the scheduler is "necessary". Consider, a long running data base
    program is writing backing store out to disk. Old behavior: the write
    absorbs as much free memory as possible to optimize disk behavior. New
    behavior: a screen saver, which is small i/o bound, causes needs resched
    to be set continually, and the write is segmented into many smaller writes.
    We now have, like NT, optimized the screen saver on a server while hammering
    file system performance. Isn't that correct?

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