In many computer systems, it's important to protect different applications or groups of applications from others. You don't want one application—whether defective or malicious—to corrupt another or prevent it from running.
To address this issue, some systems use virtual walls, called partitions, around a set of applications to ensure that each partition is given an engineered set of resources. The primary resource considered is CPU time, but can also include any shared resource, such as memory and file space (disk or flash).
Figure 1. Static partitions guarantee that processes get the resources specified by the system designer.Typically, the main objective of competing resource partitioning systems is to divide a computer into a set of smaller computers that interact as little as possible; however, this approach isn't very flexible. Adaptive partitioning takes a much more flexible view.
QNX Neutrino partitions are adaptive because:
- you can change configurations at run time
- they're typically fixed at one configuration time
- the partition behavior auto-adapts to conditions at run time. For example:
- free time is redistributed to other scheduler partitions
- filesystems can bill time to clients with a mechanism that temporarily moves threads between time partitions
As a result, adaptive partitions are less restrictive and much more powerful. In addition to being adaptive, time partitions allow you to easily model the fundamentally different behavior of CPU time when viewed as a resource.