Understanding the requirements imposed by programming model middleware on a common communication subsystem.

In high-performance parallel computing, most programming-model middleware libraries and runtime systems use a communication subsystem to abstract the lower-level network layer. The functionality required of a communication subsystem depends largely on the programming model implemented by the middleware. In order to maximize performance, middleware libraries and runtime systems typically implement their own communication subsystems that are specially tuned for the middleware, rather than use an existing communication subsystem. This situation leads to duplicated effort and prevents different middleware libraries from being used by the same application in hybrid programming models. In this paper we describe features required by various middleware libraries as well as some desirable features that would make it easier to port a middleware library to the communication subsystem and allow the middleware to make use of high-performance features provided by some networking layers. We show that none of the communication subsystems that we evaluate support all of the features.