Applicatio​n pauses for up to 4 seconds at random places in processing loop.

Question

We developed a VI that reads data from an image capture card and processes it in a loop. The processing is accomplished at near real-time approaching the 30 fps rate. Periodically, however, the entire system will hang for nearly 4 seconds. This appears to include all Windows activity. The activity monitor shows processor activity peaking (~100&) and attributes the activity to the LabVIEW process (although the monitor ceases to update during the pause). The pause occurs at random points of execution.
Multiple windows (instances of "Image Display") are updated in the loop. When these are bypassed in favor of a floating window, the severity of the problem diminishes significantly, but occurs occasionally (every couple minutes vs every 15 seconds or so).
I was inclined to blame Windows bookkeeping, but as mentioned above, the activity monitor points to LabVIEW. The problem occurs on multiple platforms (laptops) but is most pronounced on the newer dual-core system.

Answer 1

"I just reassigned the VI's execution priority to "normal" and the problem seems to have subsided. The priority was previously set to "above normal" ..."
That will expalin it if LV was doing a lot of number crunching of large data sets etc. Loops with "zero waits" will help.
LV use a concept called "Cooperative multi-Tasking" and harnesses the OS's services to provided that concept. The "Cooperative" part talks to the idea of porcesses making an efforts not to use all of the CPU without allowing other process to access the same. "Zero Waits" (zero constant wired to a wait ms) is one way that we can let LV know that tight number crunching loops can be interupted to handle other processes. The OS is involved because OS's like Windows will blindly assume that a thread that it schedules will willing give up the CPU after a while. If you don't have Zero-waits or you have heavy number crunching, the thread never releases the CPU. When you set the process to be above normal, LV and the OS did exactly what you said to do.
What exactly are you doing when LV uses all of the CPU?
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction