Distributed Light Weight Processes in MOS

摘要

Integrated multicomputer systems consist of a set of loosely coupled processors, each with its own local memory, into a single machine environment. In the distributed systems model, various user processes may run concurrently on different machines and possibly communicate to achieve a common goal. This form of concurrency encourages a programming style that uses large grain-size computation blocks. Such distributed programs consist of a set of execution entities (called threads or tasks) that perform considerable amount of work independently and communicate infrequently through messages. Threads are a convenient way of expressing concurrent programs and therefore, many programming languages embody thread-like entities in their syntax. However, the overhead of handling processes by the operating system is costly. For instance, it has been noted that the UNIX processes are heavy-weight in that they carry much associated state information. Therefore, operations on them (e.g. context switching) are slow. (RH)