[CM] [OT] jack and common lisp

Luke Crook luke at balooga.com
Wed Oct 15 19:09:12 PDT 2008

On Wed, 15 Oct 2008 13:33:10 -0700, Kjetil S. Matheussen  
<k.s.matheussen at notam02.no> wrote:
> It's a little bit harder with jack than SDL, I would think, since
> jack enjoys very much to throw out clients that doesn't
> supply data fast enough.
> Running jack in "soft mode" might
> help the situation a little bit. At least earlier "soft mode"
> made alsa "handle" xruns much much faster (by ignoring them).
> Another thing could be not to lock down memory.
> Some programs requiring large amounts
> of memory, like vmware, and sometimes also Snd,
> fails completely if memory is locked, but I don't
> know if that is the reason here.
> But frankly, since Sbcl's garbage collector most
> likely was never designed to work very well in
> hard realtime, the best solution is probably
> to send data from sbcl to jack via a lockless
> ringbuffer.

I emailed Vytautas separately and he said that the callback is being  
called 43 times per second. I have never used Jack, but that seems a  
little excessive to me. I can imagine SBCL having a fit if the callback is  
asynchronous; if SBCL is still in the callback when Jack fires the  
callback again.

- Luke

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