evals for StarOS & Medusa

Yod (h13nguye@ieng9.ucsd.edu)
Thu, 20 Apr 2000 00:39:30 -0700 (PDT)

paper9.txt -- StarOS
paper10.txt -- Medusa

Henry H. Nguyen
BS Computer Engineer
ME Computer Engineer
(858) 587 - 7046
Title: Medusa: An Experiment in Distributed Operating Sysem Structure

Medusa is a distributed, multi-user operating system that is also under
development for the Cm* multi-microprocessor computer. The goals of this
system is very much the same as to that of the StarOS system. In fact, Medusa
is the operating system that researchers at Carnegie-Mellon University develop
after they were done with the StarOS operating system. Since both operating
systems were built for the Cm* multi-microprocessor computer, Medusa also rieved
the benefits of cost-performance, reliability, and hardware adaptability that
was percieved for the StarOS operating system. The paper points out that the
design principles of the two systems are different. StarOS was concerned with
making Cm* programmable at a high level by users by providing users with object
addressing mechanism and a set of tools for manipulating parallel programs.
The Medusa, however, emphasizes problems of structure, rather than facilities.
The goal of the project was to gain an understanding of how to build
distributed operating systems and to exploit the hardware to produce a system
organization. The structure of Medusa has two significant characteristics:
One, the operating system is distributed, which means that the functionality
of Medusa is divided into disjoint utilities. Each uility is executed by a
single processor, which provide a private protected environment and implements
a single abstration for the rest of the system. Secondly, parallelism is
implicit and expected in Medusa through the message passing between utilities.
In spite of the ability to provide a variety of communication mechanisms
efficiently, Medusa design philosophy is to localize information that need
not be shared in order to increase the efficiency of a program running on it.
Title: StarOS, a Multiprocessor Operating System for the Support of Task Forces

StarOS is a message-based, object-oriented, multiprocessor operating system
that Carnegie-Mellon University implemented for the Cm* multi-microprocessor
computer, which is a system of approximately 50 processors and 3M bytes of main
memory. StarOS is designed for the support of and experimentation with task
forces, large collections of concurrently executing processes that cooperate
to accomplish a single purpose. By using many small processes, rather than a
few larger ones, this system benefits from having better cost-performance than
its counterparts. Better cost-peformance arrived from the fact that these
processors can run in parallel to maximize usage of the available parallelism
of processes within a task force. Reliability is also greatly enhanced by this
system. If an eror can be contained so that it results in the destruction of
no more than one process, the task might still be completed. The failure of
one processor does not affect the other processors in the system. Another
potential benefit of this implementation is scalability. Hardware adaptability
will be well served if the task force can grow (or shrink) with the addition
(or removal) of processor and memory resources. Being an object-oriented
system, all information is encoded and stored in objects. StarOS's objects
comprised of two portions: data portion and capability list portion. The
capability list portion defines the access rights of the data portion. Like
any other multiprocessor operating systems, synchronization and communication
between processors is a must. To support rapid message communication among
processes, StarOS implements a mailbox type of object. It's capable of
buffering messages which are either single data words or single capabilities.
Mailbox functions are send and receive. Send deliver a message to a registered
receiver, or buffer the message if the registration queue is empty and the
mailbox is not full. Receive return a message from the mailbox.