Best way to troubleshoot slow VI.

[Orion HE · Accepted solution]

Sure, I will look somewhere else for help.

[MattBradley]

Well, if you are going to mark your own post as the solution, you should do it sooner.  No sense wasting all of our time when you know the answer.  😉

[altenbach]

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Orion HE wrote:

And I am aware of the memory limitations of 32 bit OS.  But I am also aware that until you hit the wall, performance is not effected.

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While you are at it, you might also want to get away from this very simplistic and wrong concept. performance can be affected way before you run out of memory. Performance is affected as soon as you have multiple heavy CPU users running in parallel.

Some examples:

• LabVIEW arrays need contiguous memory, so the size is limited by the largest free section in memory and memory fragmentation can limit you way before you run out of ram.
• Put a couple dozens of while loops, all without a wait, inside a VI and watch how sluggish things get. Now make the VI timecritical priority... (actually, don't!;))

[Ben]

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altenbach wrote:

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Orion HE wrote:

And I am aware of the memory limitations of 32 bit OS.  But I am also aware that until you hit the wall, performance is not effected.

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While you are at it, you might also want to get away from this very simplistic and wrong concept. performance can be affected way before you run out of memory. Performance is affected as soon as you have multiple heavy CPU users running in parallel.

Some examples:

• LabVIEW arrays need contiguous memory, so the size is limited by the largest free section in memory and memory fragmentation can limit you way before you run out of ram.
• Put a couple dozens of while loops, all without a wait, inside a VI and watch how sluggish things get. Now make the VI timecritical priority... (actually, don't!;))

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I am afraid it is way beyond that state. The profile above showed the CPU's had a lot of idle time. That fact combined with the report of slow performance and the large amount of memory being used makes me think that most of the processes where in a page fail wait state due to memory thrashing. Right-click on the procces page and showing page swaps etc would either confirm or denigh that possiblity.

Ben

[altenbach]

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Ben wrote:

I am afraid it is way beyond that state.

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Oh, definitely! My comment was very generic, simply questioning some of global statements made. 😉

[Orion HE]

Update, the perceived "slowness" had to do with a dedicated touch screen on the network polling my PLC every 0ms.  I imagine not a lot of Labview users are trying to write applications in the same vein as I am.  Plus I may have not made myself clear.  Sorry for bothering so many of you.

@ Ben.  You seem to be stuck on my level of ram usage.  But I had already stated that I had several programs open so that I don't have to shut them down and reopen them constantly.  At no point did I complain about PC performance, though you may have thought that my VI performance was based on sluggish PC performance, that concern should have been abated when I told you of all of the programs I run and showed the processor spec of my computer.  There is no thrashing, as I am not using the virtual memory, I have plenty of physical memory left over.  And right now, I running my VI, I get 0 hard faults per second.

[Ben]

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Orion HE wrote:

Update, the perceived "slowness" had to do with a dedicated touch screen on the network polling my PLC every 0ms.  I imagine not a lot of Labview users are trying to write applications in the same vein as I am.  Plus I may have not made myself clear.  Sorry for bothering so many of you.

@ Ben.  You seem to be stuck on my level of ram usage.  But I had already stated that I had several programs open so that I don't have to shut them down and reopen them constantly.  At no point did I complain about PC performance, though you may have thought that my VI performance was based on sluggish PC performance, that concern should have been abated when I told you of all of the programs I run and showed the processor spec of my computer.  There is no thrashing, as I am not using the virtual memory, I have plenty of physical memory left over.  And right now, I running my VI, I get 0 hard faults per second.

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Thank you for the update! it helps us help othres in the future.

Re "...not a lot..."

agreed!

One of my rookies (mellowbuck) wrote the app featured in figure 2 of this KB article.

 

In his case he was talking to a cFP from a LV touch panel app.

Ben

PS please mark your update as a reply to make it easier to find. Again thanks for the update.