INFORMATION TECHNOLOGY ARCHITECTURES

Information Technology Architectures

Information Technology Architectures

Introduction

Real-time operating systems or RTOS are an important class of operating systems. Like all operating systems, RTOS can be examined from a variety of perspectives, including theory and actual implementation. An RTOS is defined as...:"...the one in which the correctness of the computations not only depends upon the logical correctness of the computation but also upon the time at which the result is produced. If the timing constraints of the system are not met, scheme failure is said to have occurred."

QNX Real-time OS

The main responsibility of any operating system is to manage a computer's resources. Some system processes call for strict resource management and scheduling. These processes depend on the OS to handle multiple events and to ensure that the system responds to those events within predictable time limits. The QNX philosophy is that the more responsive the OS, the more "time" a real-time application has to meet its deadlines.

Architecture

The heart of the QNX OS is the Neutrino kernel. It can be scaled to very small sizes with a fully functional core kernel of only 12K. The Neutrino kernel conforms to the POSIX-standard API.

Scheduling

When building an application (real-time, embedded, graphical, or otherwise), the developer may want several algorithms within the application to execute concurrently. inside Neutrino, this concurrency is accomplished by utilising the POSIX thread form, which characterises a method as containing one or more gist of execution. (Jason Hopes 2007 Pp. 77)

When thread is pre-empted

The running thread is pre-empted when a higher-priority thread is placed on the ready queue (it becomes READY, as the result of its block condition being resolved). The pre-empted thread remains at the start of the ready queue for that priority and the higher-priority thread runs.

When thread yields

The running gist voluntarily yields the processor (sched yield()) and is put ...