LabVIEW
Labview 8 Performance , FGV's very very slow. Stuck,Need solution ASAP.
Hi,
I have a very STRANGE issue here, I migrated my working Labview 7.1.1 RT code to Labview 8.0 and noticed the performance degradation beyond acceptance level.
I use "RT Simple CPU Usage.VI" to check the CPU resources. I usually poll the FPGA cards in a time critical VI, (I have 2 FPGA cards). After polling I use a FGV to transfer it out into a normal priority thread and process it. In Labview 7.1 my CPU Usage never exceed 40%. However in labview 8 it’s a constant 100% . I have attached a screen shot of my 7.1 Vi's which have been migrated to 8.0.
The processing would be comparing values, storing to disk etc. However, the FGV’s in Labview 8 are hogging up the resources and that seems to be the bottle neck. ( I disabled every other loops/ tasks inorder to come down to this conclusion). I also tried using the so called "Shared variables w/FIFO's enabled" and the result is still the same. if i disable the reading of the FGV's, my idle usage with polling is 20%. This doesn't make sense to me, in theory what works in LV 7.1 should work in 8.0.
Also, I cannot switch to LV7.1 once 8.0 is installed. Does anyone know the dependencies required to bring it back to 7.1 through the MAX "add/remove software"?
Please advice.
- Yes, I did change the timed loop to a regular while loop with a "wait until next ms" with 1 ms. and i played around with the Normal priority VI until I saw the CPU usage come down. Basically I started the NPL to a 100ms and gradually came down. The conclusion was anything less than 25ms caused the CPU to peak at 100%. This latency is simply not acceptable considering what is required.
- I reinstalled Labview 8 on a fresh PC to make sure that no version issues existed with 7.1 and 8.0, still no go.
- Mass compiled all VI's.
- Took the same above example and replaced the FGV with Shared variables and the result is the same.
- Put additonal benchmarks for calculating the time required to execute each part of the code by getting the tick count and tickcount after the code is executed in a sequence structure. The sad answer is the difference was ZERO.
- Within the timed loops, also check whether "Finished Late" turned on. Answer = NO.
Anything else which I can do to investigate?
Steven,
Need to add to your comments on my second question. I uninstalled the Network Variable Engine and the Variable Client Support, but you would also need to downgrade the NI-RIO to 1.4, only then will it allow you to install LV7.
However, this did not solve my problem because a 78433R was not recognized in the MAX(Needed NI-RIO 1.3, which Magically disappeared as an option) . Hence, uninstalled all NI products, 7.1/8.0 and reinstalled. A few hrs later
Same old code is perfectly stable in 7.1.1, allowing me interthread transfer @ 1ms.
So this may be an issue which someone may want to recreate on their systems.
Until this problem is solved, I cannot migrate to LV8.
Regards,
Ash
Steven, Ben.
Yes, the link is correct. However, I did try this before. I had removed the VI's which were polling the RT CPU usage and enabled the Real time system manager. The Results were the same and the inter thread transfer did not improve.
Within the RTSM my CPU also spiked and hovered around 70-80%. Which is too much
From prior experience, the RTSM adds additional overhead to update the memory usage and CPU usage on the CPU. Disabling the memory checkbox yields a bit bettor usage but still below 7.1.1 acceptance level.
I am really stumped on this problem and haven't done any further experiments with LV8.
Regards,
Ash
