Subroutine is a priority setting in the VI Execution properties. From the LabVIEW Help:
Select subroutine priority to make the LabVIEW execution system run the VI as efficiently as possible. VIs that you set for Subroutine priority do not share execution time with other VIs. Selecting the subroutine priority also prevents any screen redraws and other system functions from occurring. You cannot abort a VI that has subroutine priority.
When to use the Subroutine Setting
- VIs that are atomic and should not be preempted by other calls
- Use when you have plenty of VIs that perform simple computations. It removes overhead of calling each.