Unexpected slow down in VI

[tlantzspi]

I have a large VI that is running data aquisition and control on our system.  Recently it has been have some troubles.  After running for a period of time (anywhere from a couple hours to several days) it stops updating once a second, and begins to update once every 25 seconds.  The data updates are from a UDP stream that is pulled from our system every second.  Some version of this VI has been running for on and off for about 9 years and we have never observed this problem before.  In this state it also does not respond to the built in 'stop command' - which gracefully stops the whiles loops/data files, however, it can be stopped using the hard execution stop.  Starting the VI again after stopping it and it is back to normal with no problems. 

This started occuring after we rebuilt the laptop that the VI was running on.  We backed up the VI and are running the same version that was running before the system was rebuilt.  The slow down does not occur after any set number of data points or time, just randomly.  A VI running simultaneously pulling data from the same source as this one does not have any trouble/slow down - this VI is always running concurrently, so it is not a source of the problem.  The task manage doesn't indicate that the CPU is bogged down, or that any other applications are running in the background.  The computer is on an isolated network with about 5 other machines, all of which are pulling data from different sources.

Is there a way to determine where the VI in it execution while it is running?  Anyone else had problems with a VI slowing down after rebuilding a computer?  Any hints as to where I should start looking for my problem.

[josborne]

Sounds like you need to do some basic debugging.  My reccomendation would be to read this first:

http://decibel.ni.com/content/docs/DOC-1695 

And then:

1. Open the VI and make sure you can view the diagram.

2. Run the VI

3. Wait for it to freeze.

4. Click the "lighbulb" to enable execution highlighting after it has frozen, and you should be able to find where it has frozen.

If that doesn't work, I sometimes like to output an application "status" to the front panel using a simple string indicator.  Just write some text to the indicator at the beginning of every step in the VI.  This could also be used to track what is hapenning when the VI freezes. 

[altenbach]

What is the OS? What are the firewall settings? Do you have an updated driver for the network card?

25 seconds is suspiciously similar to the default UDP timeout for UDP read. This might give you a clue where to look. 😉

[tlantzspi]

Thanks for the UDP Read timeout help.  Hopefully there was a problem with the firewall settings.  I disable the firewall, and have yet to have a problem.  I will keep my fingers crossed.