[Rtai] Source of big latencies???

Federico Bergero fedebergero at gmail.com
Mon Sep 26 16:12:43 CEST 2011


Hi I'm working on a project with rtai.
I'm using a Intel i7 with 6 cores and HT so Linux sees 12 cores.
I'm running a real time LXRT-RTAI thread on each core (indicating RTAI
to do so with the cpus_allowed mask).

Each thread runs a simulation of a system syncrhonized with real time,
and I'm using rt_sleep/rt_busy_sleep to do the waits.
When running the simulation SOMETIMES I get a max latencies of 900us
on some processor and 2us on others processors.
These BIG latencies occur randomly. Sometimes everything runs smoothly.
What could be the source of these lantencies? I have turned off Freq
Scaling in Linux and SpeedStep in the BIOS.

Also I don't quiet understand how the rt_get_cpu_time_ns() is
implemented on a SMP system, could someone explain me this?

Thanks Fede

-- 
I find television very educational. Every time someone switches it on,
I go into another room and read a good book.


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