Hello all,
I was wondering what people used to check RT_PREEMPT behavior under
load/stress?
I'm trying to test the accuracy of my timers and have a test where I
setup a kernel module with an hr-timer flipping RTS bit on serial COM0
periodically, which I can look on an oscilloscope. the scope triggers on
rising edge, I call jitter what shows on the falling side:
under no specific load I get ~ 10 us (worst case waiting a long time)
My initial idea for stressing the system was to compile a kernel, make
-j 8 (#cores) that I thought would exercise CPU and IO if anything. As
it happens, it's "mostly good" but I do get occasional (but repeatable)
wild excursions (>100us)
Looking around, I found a tool called 'stress' -
http://weather.ou.edu/~apw/projects/stress/
Under these new conditions, the system behaves really well again ~20 us
stable all the way.
So both tests give different result, I'm not sure which to trust.
I was thinking maybe there is some weird interaction with the kernel and
building the kernel that make the 'bad' test invalid?
I have RT_PREEMPT 3.0.18-rt34 SMP x86_64
Thanks,
--
Matthieu
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