Interrupt latency test bench on RTAI (StrongArm port)

[Clément Moreau]

Hi,

On our own StrongArm based board, we need a good latency on one external 
(GPIO) interrupt.

I decided to use RTAI 24.1.9 over linux-2.4.17 because i could not achieve 
this latency with linux-2.4.17 alone.

I have done a test bench of the gpio irq latency, and i found that the mean 
latency is very good (about 5 us), but the worst case latency is not good : 
over 300 us.

My setup is : an external timer, that generate a rt irq each 1 ms.
There is no rt task, no other rt irq, but a lot of linux irqs.

It seems that our ethernet chip linux irq (cs8900, with standard arm linux 
driver) is disturbing real time irq process.
Is it possible ?
Does any body have the same problem or know the solution ?

Thank you.


-- 
Clément Moreau
Inventel Systèmes -- www.inventel.com
PARIS