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    SubjectRe: No 100 HZ timer !
    On Mon, 9 Apr 2001, Alan Cox wrote:

    > > > Its worth doing even on the ancient x86 boards with the PIT.
    > >
    > > Note that programming the PIT is sloooooooow and doing it on every timer
    > > add_timer/del_timer would be a pain.
    >
    > You only have to do it occasionally.
    >
    > When you add a timer newer than the current one
    > (arguably newer by at least 1/2*HZ sec)

    That's only if we want to do no better than the current system. We'd want
    a new variable called timer_margin or something, which would be dependent
    on interrupt source and processor, and could be tuned up or down via
    sysctl.

    > When you finish running the timers at an interval and the new interval is
    > significantly larger than the current one.

    Make that larger or smaller. If we come out of a quiescent state (1 hz
    interrupts, say) and start getting 10ms timers, we want to respond to them
    right away.

    > Remember each tick we poke the PIT anyway

    We could also have a HZ_max tunable above which we would not try to
    reprogram the interval. On older systems, this could be set at
    100-200HZ...

    --
    "Love the dolphins," she advised him. "Write by W.A.S.T.E.."

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