Re: Bad MIDI performance : 10ms latency instead of the expected
Benno Senoner (sbenno@gardena.net)
Fri, 27 Aug 1999 00:26:14 +0200
On Thu, 26 Aug 1999, Alan Cox wrote:
> > > 200bytes/sec is just rudiculous , how do you plan to drive an external synth
> > > with that little MIDI bandwidth ?
> >
> > I need a timer around 2000Hz for some good code. I won't support polling
> > mode (busy loop) in any case.
>
> Then your code will never be usable. Some hardware sucks, you have to do
> limited polling with a timer backoff. A well tuned polling loop will often
> work out nicely providing you are careful. Remember with irqs on you are
> just like busy in userspace no worse. You can even do
>
> while(poll_input()==0)
> {
> if(current->need_resched())
> schedule();
> }
>
> sort of stuff
Do you think there are some benefits by inserting the re-schedule in the
drivers/sound/mpu401.c file ? ( less CPU usage)
for (timeout = 30000; timeout > 0 && !output_ready(devc); timeout--);
But since the FIFO is only 2 bytes long = 600usecs,
the schedule() could cause a MIDI bandwidth decrease,
but would keep CPU load down , right ?
Why was the MPU401 code not tuned that way ?
regards,
Benno.
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