Re: [rtl] Interrupt Jitter

[Paolo Mantegazza <mantegazza@aero.polimi.it>]

Cort Dougan wrote:
> 
> } What does <20 us mean. Under what load. If it is 10 to 20 I got it with
> } a stock portable G3 MAC. If I avoided ping -f I could get even less than
> } 5 us. But it does mean nothing.
> 
> Yes, low 10's (us) is about typical for Apple hardware.  I addressed you
> specifically because you suggested stock hardware couldn't do that.  Now I
> see that you have seen better than 20us from your stock Apple.

Yes but, I'll repeat, it is meaningless. The lowest figures are just far
almost do nothing but real time activity. People are often using
RTL/RTAI just because they can do real time and whatever elase. So it is
enough to start some heavy disk filing, jam the ram cauche and cause
page faults, do a lot of net work and the figures run higher. It is not
bad, but people must have it clear, after all it is something that will
hit whatever real time OS they are using.

It also make it clear that if tehy want RTL-RTAI best figures as a worst
case they must use DSPs.


Ciao, Paolo.