RT target is running at 99.8% CPU

[Ben]

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Hillman wrote:

Hi Ben,

I was indeed confirming - as you seemed a little unsure when I read the post yesterday. 

I was wondering if the question concerning the cRIO had be resolved?

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Thanks James!

I was wondering the same thing and have an emoticon for just this occation.

 

Ben

PS Solved icon can befound here or if you want to find it just enter the search phrase "Solved icon".

[Jeremy_B]

Hi,

I ran my test on a cRIO-9014, both in scan mode and with the FPGA interface, so I don't think you should see this behavior on the cRIO.

What happens if you slow the loop down from 40 ms to say, 500 ms?  The timed loop has some statistics on the input node if you expand it out, you can use that to see if it is missing deadlines.  You have a fair amount of signal processing, I'm wondering if that is just maxing it out.

[suni]

Hi

Thanks for the reply.

I checked CRIO cpu usage using distributed systems manager. There is also real time systems manager to check cpu usage of RT controller. I couldn't get this to see any info about cpu. In distributed systems manager I was able see cpu usage. Do these system show same information?

I slowed the loop rate and still showing 99% cpu usage. Thanks very much for your help

[Jeremy_B]

Hi,

In the real time system manager, you have to enable CPU usage tracking, there is a checkbox for it.

Put an indicator on the finished late indicator on the timed loop and see if it is meeting its timing.

[suni]

I enable CPU usage tracking still didn't show anything. I have tcp port selected as 3363. Does that need to be changed? Thanks.

[Jeremy_B]

Do you have VI server enabled on the 9014?

[suni]

i did select tcp in vi server configuration page in RT tartget.

[jkurtw]

Hi Suni,

Are you programming CompactRIO in scan mode?

If so, what do you have the scan period set to? Here is a table from the NI Scan Engine benchmarks page: http://zone.ni.com/devzone/cda/tut/p/id/7792

Number of Channels (AI/AO pair)	100 Hz	500 Hz	1000 Hz
1	10.29%	31.53%	54.71%
16	15.5%	47.41%	94.96%
32	17.98%	66.58%	n/a
64	26.62%	96.22%	n/a
80	28.61%	n/a	n/a

As you can see from the chart, if you have a high channel count and are running the scan period at 500Hz or higher, it can use quite a bit of CPU.

You can check the scan period by right clicking on the cRIO controller in the project and selecting Properties >> Scan Engine.

If you don't need a high I/O scan rate, slow down the scan period and you will get CPU back. 

 Kurt 

Message Edited by jkurtw on 02-25-2009 09:29 PM