Christian Tannert wrote:
>
> Hello,
>
> I got a little problem with running the stress example in rtai-1.3.
> This example shows the preemption and latency tests under intense load.
> With the preemption everything works fine. I can see on console with the
> checkp program that the slow task is preempted from the higher prior
> fast task. But if I start the latency program (checkl) I always get 0
> for min, max and average, whatever load I do (i.e. ping -f ). What did
> I wrong ?
>
> I use SuSE 6.2 Kernel 2.2.14, CPU 80486. I set in rtai.h CPU_FREQ to
> FREQ_8254. /dev/rtf* are installed.
>
> Thanks a lot in advance
> Christian
It is possible that last one of us that tested it before releasing has
checked such a test with the periodic timer and left it that way.
Look at the macro defining ONE_SHOT in rt_process.c and see if it is
commented. In such a case uncomment it and you'll get what you want.
Since you are likely checking it on a 486 you'll get results strongly
influenced by the need of reading the 8254 timer, as there is no TSC to
measure it. It would be better for you to stay in periodic mode and use
a scope to verify the latency on 486s. Beware also of the ticking
frequency.
It is not a bug, the latency check is done with the timer resolution and
having zero in periodic mode simply shows that you are not loosing
ticks.
Ciao, Paolo.
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