LabVIEW Real-Time 8.20 Performance Improvements

The LabVIEW 8.20 Real-Time Module includes many performance improvements over previous versions to help you optimize your applications that require high reliability and deterministic control. This document reviews some of the hardware and software improvements.

PID Control

The PID control functions included with LabVIEW 8.20 Real-Time Module have significant performance improvements over previous versions. The control code has been optimized for better performance, especially in cases of multiple channels as shown by the chart below.


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RT FIFOs

The LabVIEW 8.20 Real-Time module also has a new set of real-time FIFO VIs for interthread communication. Real-Time FIFOs are important mechanisms for passing data between multiple threads within a real-time application, without inducing jitter.


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Single-Point IO

With improvements in the LabVIEW 8.0 and LabVIEW 8.20, as well as improvements in driver software; single-point IO performance for control has improved in most cases. One test done to benchmark performance finds the maximum sustainable rate on various controllers to perform an analog input read, a PID control algorithm, and an analog output read. The following tables show the performance improvements for various configurations of hardware.


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This article (and LabView as whole) has a very weak point in UNDEFINED responsivness. In an average 10 MIPS real-time system you can ENSURE, that the ISR starts performing in 1us if you really want it. In a real-time control the number of available operations per second is often not so important as the fact, that the I/O operations like ADC read must happen in EXACTLY defined time and that the responses to external events must happen in certain time limits. In my opinion real-time control in LabView and on a hardware where you have all the perverse PC dirty tricks like "cache memories" x86 "architecture" and multithreaded "Real Time" OS (this is a contradiction) is a nightmare. Just "stability" is less then sufficinet.
- Jan 3, 2007