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    SubjectRe: [PATCH] i386: Selectable Frequency of the Timer Interrupt
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    On Mon, 2005-07-11 at 21:30 -0700, Martin J. Bligh wrote:
    > Some sort of comprimise has to be struck for now, until we get sub-HZ
    > timers. I'd prefer 100, personally (I had that set as default in my tree
    > for a long time). Some people would prefer 1000 or even more, maybe.
    > 250/300 seems like a reasonable comprimise to me. Exactly what problems
    > *does* it cause (in visible effect, not "timers are less granular").
    > Jittery audio/video? How much worse is it?

    OK, here's a real world example, taken straight from the linux-audio-dev
    list today.

    Lee

    Lee Revell <rlrevell@joe-job.com> :
    > On Tue, 2005-07-12 at 20:57 +0200, Kjetil Svalastog Matheussen wrote:
    >> E-radium has been tested with both the 2.4 kernel and the 2.6 kernel
    >> and with a ~1GhZ machine and a ~2ghz machine. (A 2.4 kernel with a
    >> 100hz resolution timer will proably not work very nice though.)
    >
    > Can you please explain why 100HZ would be a problem for your app? Right
    > now the kernel people are trying to change the default HZ for 2.6 to
    > 250. I have told them that this is insane but they seem inclined to do
    > it anyway.
    >

    The program use poll to sleep. If the resolution of the kernel is 100Hz,
    there would sometimes be a too long delay of up to 10ms (and probably beyond)
    before the program is woken up, and before a midi message is sent,
    which can cause music to stutter.

    Simple as that. :-)

    > If you can provide more examples of apps that would be broken by this
    > change maybe we can convince them not to change it.
    >

    Hmm, mplayer I guess...
    Don't know how muse, rosegarden, seq24 etc. handles timing...
    But all midi-sequencers that doesn't use /dev/rtc could suffer. (?)


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