Re: [FFADO-devel] irq priorities howto posted

[Stefan R. <st...@s5...>]

Jörn Nettingsmeier wrote:
> Stefan Richter wrote:
[...]
> i've tried to work this into
> http://subversion.ffado.org/wiki/IrqPriorities. i'd appreciate if you
> and other ffado-devel patrons could verify it for correctness eventually.

Looks good to me.

>> Since ohci1394 isochronous receive tasklet and isochronous transmit
>> tasklet sit between ohci1394's top half and FFADO/ Jack userspace, I
>> conclude that latency of tasklet execution is important for audio latency.
> 
> ok. i've noted that, but was reluctant to actually raise its priority.
> can anybody fill in this blank and add a good recommendation?
> 
> maybe it should be somewhere between the audio-specific IRQs and the
> normal IRQs?
> then again, the default is 49, which is below any IRQs, so i don't know
> if raising it can mess things up...

I suppose the tasklet thread should not get higher priority than any
(top half) IRQ thread, probably also not higher than some of the other
soft IRQ threads.  It may or may not be beneficial to prioritize the
block layer's soft IRQ and networking soft IRQs lower than the other
soft IRQs since they deal with asynchronous things that don't require
very low latency.  However, unless somebody finds actual evidence that
such changes would improve things, these priorities are better left
untouched.
-- 
Stefan Richter
-=====-==--= =-== ---=-
http://arcgraph.de/sr/