[linux-audio-user] Re: [linux-audio-dev] [ANN] E-Radium V0.61b

[Florian Schmidt]

On Tue, 12 Jul 2005 22:35:24 +0200 (CEST)
"Kjetil Svalastog Matheussen <k.s.matheussen at notam02.no>"	<k.s.matheussen at notam02.no> wrote:

> > 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. :-)

Some semieducated blabbering ahead (might be all wrong):

I think i once read that interrupt handling "short circuits" the linux
scheduler (in the sense that not only at every timer interrupt but also
at the end of finishing any interrupt handler the kernel looks which
processes are ready to run etc. and maybe there's a high prio process
waiting just for that interrupt (by i.e. polling or reading on a device
file). 

So for all those realtime processes that depend on events that are
triggering interrupts (like soundcards' irqs) the timer interrupt really
doesn't matter. I'm not sure at all though this applies to midi handling
(and especially to alsa_seq when routing from one app to another) or is
even correct in any sense at all :)

Anyone can shed light? 

Regards,
Florian Schmidt

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