Steven Rostedt wrote:
On Tue, 2010-05-11 at 17:30 +0200, Asier Tamayo wrote:
Hello Nivedita,
Thanks for your answer.
What are your criteria? Do you care about anything other
than performance (availability, upgrades, cost, support,
compatibility, tools, ...)?
(...) you're best off testing the solutions that you can
get hold of with your own workload, in your own environment.
Performance is a must. Besides, costs and tools are very important.
Support is also important, but I guess I'd find some good support for
any of the solutions.
My new CPU has an Intel Atom N270 @1.6 GHz processor. At the moment
(during the porting it might be optimized), I have 5 drivers requering
hard real-time (no loop can be skipped) and being called every 2 to 10
ms. In fact, at the beginning I was using 1 ms, but I had some
problems with the hard real-time and changed the timing to 2 ms. I do
not consider using a legacy OS emulation.
If tuned properly, PREEMPT_RT can easily handle 1ms requirements. On a
standard x86 CPU (we support others than x86) our goal is never to be
I did a test with user space based CAN driver.
Already the standard distribution of SUSE 11.2 (non RT) was able to
handle 1000 frames per seconds sent by a QNX6 machine !!
The PREEMPT_RT version of SUSE 11.2 is much, much faster :-)
over 100us in reaction time.
The latency test of PREEMPT_RT shows a latency of ~10us for a dual-core
box at 1.8GHz.
--Armin
http://www.steinhoff-automation.com
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