Disabling lapic timer for a certain core

["M. Koehrer" <mathias_koehrer@arcor.de>]

Hi all!

I am running the RT_PREEMPT kernel 2.6.31.2-rt13 on a Intel Quad Core CPU.
I start my kernel with isolcpus=1-7 option to force all processes to run on CPU core 0 only.
Now we have the need for a very fast loop. Within this loop some accesses from/to a PCIe I/O board
(mapped in user space) and some additional computation has to be done.
For this, I use a real time thread, run this on CPU core 3 and let it run in an endless polling loop.
So far everything works fine.
This thread is the only running user mode thread on CPU core 3.
However, we measure some run time jitters when accessing the I/O board in the range of up to 
15 microseconds which are not tolerable by the application.
I see that on all cores the "Local Timer Interrupt" occurs 100 times a second (of course this is the timer frequency 
select in the kernel configuration).

My question is now:
Is it possible to disable the "Local Timer Interrupt" for core 3 as it is actually not required here?
I want to use the full 100% CPU core time for this single loop.

Any help or ideas are welcome!

Thanks a lot.

Regards

Mathias

-- 
Mathias Koehrer
mathias_koehrer@arcor.de


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