INtime® 3.1 Software - tenAsys

Chapter 5: Designing RT applications
Target environments
Methodology
Developing INtime applications involves balancing between the target environments:
• The RT environment, where you create portions of the application that require
RT robustness and determinism.
• The Windows environment, where you can add RT object access to a
Win32 application.
A critical aspect of any INtime application is the division of labor between Windows
processes and RT processes and, to a finer degree, between the threads in each process.
Important guidelines for developing RT user applications include:
• Limit RT processes to performing only time-critical functions: For maximum
performance, applications must be divided appropriately between the RT and
Windows portions. The INtime software scheduler gives precedence to RT
processes and threads. This preferential scheduling guarantees the best possible
RT response.
For example, to optimize user interface (UI) performance, design INtime
applications so that RT activity occurs in event-driven bursts. An INtime
application that executes for too long on the RT kernel can consume too many
CPU cycles and therefore degrade the system’s Windows capabilities. This
typically causes a sluggish GUI on the Windows side.
Note
Adverse effects in the Windows interface, disk and network operation become noticeable
when RT CPU utilization on your system exceeds 70 percent. On a multi-core computer
configured for dedicated mode, INtime software can consume close to 100 percent of its
processor without affecting Windows.
• Determine which Windows threads require the greater relative priority: The
relative priority given to each of the Windows threads of an INtime application can
determine the perceived performance of the application in a heavily loaded
system. The higher the relative priority given to a Windows thread, the more likely
the thread will perform sufficiently in a heavily loaded system.
Determining which threads require the greater relative priority depends on the nature
of the application. For example, giving higher relative priority to data manipulation
and data storage threads can sacrifice data display and user interface performance
when the system is heavily loaded. If an application is data-intensive or the system
has no keyboard or display, then sacrificing user interface performance may be
desirable. Conversely, if a requirement of an application is a responsive user
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