Книга: Distributed operating systems

9.1.2. Goals of Chorus

9.1.2. Goals of Chorus

The goals of the Chorus project have evolved along with the system itself. Initially, it was pure academic research, designed to explore new ideas in distributed computing based on the actor model. As time went on, it became more commercial, and the emphasis shifted. The current goals can be roughly summarized as follows:

1. High-performance UNIX emulation.

2. Use on distributed systems.

3. Real-time applications.

4. Integrating object-oriented programming into Chorus.

As a commercial system, much work focuses on tracking evolving UNIX standards, porting the system to new CPU chips, and improving performance. The company wants Chorus to be seen as an alternative to AT&T UNIX, re-engineered, easier to maintain, and oriented to future user requirements.

A second major theme is the need for distribution. Chorus is intended to allow UNIX programs to run on a collection of machines connected by a network. To support distributed applications, various extensions have been added to the programming model. Some of these, such as message-based communication, fit easily in the existing model. Others, such as the introduction of threads, required a rethinking of existing features, such as UNIX signal handling.

A third direction is the introduction of support for real-time applications. The approach taken is to allow real-time programs to run (partly) in kernel mode and have direct access to the microkernel, without any software in the way. User control over interrupts and the scheduling algorithm are also important here.

Finally, another goal is the introduction of object-oriented programming into Chorus in a clean way, without disturbing existing subsystems and applications. How this is being done will be described in detail later in this chapter.

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