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    SubjectRe: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.31-19
    On Thu, 2 Dec 2004 09:40:40 +0100
    Ingo Molnar <mingo@elte.hu> wrote:

    > > actually a single client doing nasty (non RT) stuff in its process()
    > > callback can "starve" jackd. AFAIK jackd waits until the last client
    > > has finished its process callback. So, if some client's process
    > > callback decides to use (for example) some blocking system call (big
    > > no no) and consequently falls asleep for a relatively long time, then
    > > it can cause jackd to miss its deadline. I'm not sure though wether
    > > this triggers an xrun in jackd or just a delay exceeded message.
    >
    > since the period size in Rui's test is so small (-p64 is 1.6 msecs?),

    ca. 1.3ms

    > the 2.6 msec timeout in pipe_poll() already generates an xrun.

    yep. now the question is: why did jackd have to wait so long for the
    client? what was the client doing? was it sleeping? what client was it?
    probably not the simple jack_test client, right?

    Short tests ((20 minutes, due to lack of time) with cvs jackd and a
    number of modified jack_test clients (added a for loop in the process()
    callback to burn cycles to increase the cpu load) show no xruns here
    even with relatively high cpu load (around 70%) and a periodsize of 64
    frames. Of course i had the mandatory additional kernel compile running
    in the background :)

    flo

    Oh wow. Just before hitting send i got three xruns of around
    0.020-0.050msec. Ok, will read up on recent emails to see what to do to
    debug these.
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