Re: [rtl] DMA (latencies and jitter)

[Stuart Hughes <sehughes@zentropix.com>]

> Giovanni Racciu wrote:
> 
> It is a matter of fact that heavy DMA can affect (increasing)
> latencies and jitter. In our actual solution the software is running
> on a dedicated PC104 board, which is not corrupting the latency. But
> as a future develpment we would like to put it on a standard PCboard
> and the entire Linux OS plus the applications will run on it (using
> all the hardware features in a massive way).
> Is there anybody who has an idea on how big (worst case) could be the
> increasing latency and gitter ?
> 
> Thank you.
> 
> Ciao
> Giovanni Racciu
> 

Hi Giovanni,

I have attached a jitter measurement routine I use.  On my laptop 233MHz
PII with a BX motherboard, I get +/30usec jitter worst case (RTL or
RTAI).  This is under various kinds of loading.  Your mileage may vary
(expecially with the use of DMA devices).

Regards, Stuart

jitter.tar.gz