Hello. I need some help or maybe just advice of right use of
realtime-kernel. We are(company where i work) now developing PLC based
on Variscite VAR-SOM-AM33 processor
module(http://www.variscite.com/products/system-on-module-som/cortex-a8/var-som-am33-cpu-ti-am335x-am3354-am3352).
Variscite provides it with kernel version 3.12. I've patched it with
patch-3.12.10-rt15 and chose Full Preemptible Kernel(RT) preemption model.
As result when i run cyclictest(like said in wiki -
https://rt.wiki.kernel.org/index.php/Cyclictest) with no other load in
system, i've got following results:
cyclictest -t1 -p 80 -n -i 10000 -l 10000
System without RT-patch:
T: 0 ( 1399) P:80 I:10000 C: 10000 Min: 35 Act: 69 Avg: 63 Max:
247
System with RT-patch:
T: 0 ( 1534) P:80 I:10000 C: 10000 Min: 39 Act: 61 Avg: 61 Max:
91
So it works.
But when i enable load with codesyscontrol-system(about 80% CPU load), i
have following results:
System without RT-patch:
T: 0 ( 1412) P:80 I:10000 C: 10000 Min: 8 Act: 16 Avg: 13 Max:
572
System with RT-patch:
T: 0 ( 1549) P:80 I:10000 C: 10000 Min: 11 Act: 14 Avg: 17 Max:
2492
Is it normal that max jitter in system with RT-patch more(almost 5x
time) than in system without RT-patch, in this case?
Sorry, if this question silly. I've used only DOS-like(one-task) systems
earlier and wrote firmwares with one task only in embedded systems, and
Linux only on desktop and servers, without realtime.
Thanks, in advance.
--
Best regards, Sergey.
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