[PD] PD and latency on kernel

Frank Barknecht fbar at footils.org
Sat Nov 19 09:20:35 CET 2005

Christian Klippel hat gesagt: // Christian Klippel wrote:

> hello iohannes and all,
> Am Samstag 19 November 2005 00:13 schrieb IOhannes m zmoelnig:
> [...snip...]
> >
> > please note, that the word "latency" is nowhere mentioned. it has
> > nothing to do with "realtime". (you can have a hard realtime system that
> > has a delay of 1 week).
> > so pd is by design a realtime system.
> >
> ouch! that comment about hard realtime is plain wrong.
> hard realtime is used in systems where you need minimal delay, like engine 
> controls, medical systems, etc.
> imagine your life support systems would use hard realtime that can delay up to 
> a week .....
> the most important aspect of hard realtime systems (like rtlinux) is that they 
> have the lowest latency possible!
> also, see here: http://en.wikipedia.org/wiki/Real-time_computing

There I read something different, though: 

  A distinction can be made between those systems which will suffer a
  critical failure if time constraints are violated (hard or immediate
  real-time), and those which will not (soft real-time).

Note that this doesn't mention the size of the latency at all, it just
speaks about violations of "time constraints", which themselves could
be nanoseconds or years. Later on the same page: 

  It is important to note that hard versus soft real-time does not
  necessarily relate to the length of time available. 

Q.e.d. ;)

 Frank Barknecht                 _ ______footils.org_ __goto10.org__

More information about the Pd-list mailing list