Re: PREEMPT_RT vs ADEOS: the numbers, part 1

[Ingo Molnar <mingo@elte.hu>]

* Karim Yaghmour <karim@opersys.com> wrote:

> Ingo Molnar wrote:
> > how were interrupt response times measured, precisely? What did the 
> > target (measured) system have to do to respond to an interrupt? Did you 
> > use the RTC to measure IRQ latencies?
> 
> The logger used two TSC values. One prior to shooting the interrupt to 
> the target, and one when receiving the response. Responding to an 
> interrupt meant that a driver was hooked to the target's parallel port 
> interrupt and simply acted by toggling an output pin on the parallel 
> port, which in turn was hooked onto the logger's parallel port in a 
> similar fashion. We'll post the code for all components (both logger 
> and target) for everyone to review. There's no validity in any tests 
> if others can't analyze/criticize/ duplicate.

ok, this method should work fine. I suspect you increased the parport 
IRQ's priority to the maximum on the PREEMPT_RT kernel, correct? Was 
there any userspace thread on the target system (receiving the parport 
request and sending the reply), or was it all done in a kernelspace 
parport driver?

	Ingo