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On the Design of Chant: A Talking Threads Package
INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA
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Lightweight threads are becoming increasingly useful in supporting parallelism and asynchronous control structures in applications and language implementations. However, lightweight thread packages traditionally support only shared memory synchronization and communication primitives, limiting their use in distributed memory environments. We introduce the design of a runtime interface, called Chant, that supports lightweight threads with the capability of communication using both point-to-point and remote service request primitives, built from standard message passing libraries. This is accomplished by extending the POSIX threads interface with global thread identifiers, global thread operations, and message passing primitives. This paper introduces the Chant interface and describes the runtime issues in providing an efficient, portable implementation of such an interface. In particular, we present performance results of the initial portion of our runtime system point-to-point message passing among threads. We examine the issue of thread scheduling in the presence of polling for messages, and measure the overhead incurred when using this interface as opposed to using the underlying communication layer directly. We show that our design can accommodate various polling methods, depending on the level of support present in the underlying thread system, and imposes little overhead in point-to-point message passing over the existing communication layer.
APPROVED FOR PUBLIC RELEASE