Application-level load migration and its implementation on top of PVM

Abstract

The development and experiment of a load (process) migration scheme conceptually similar to moving house is described. The basic idea is to migrate a process by starting a new process on another processor with checkpoint data prepared by the old process itself but transferred automatically by the migration system. The new process will then unpack the data and resume the computation. The migration mechanism of our facility is implemented by a set of library calls on top of PVM. It performs functions such as freezing and unfreezing communications, checking load conditions, selecting destination processors, starting new processes and receiving migrated data. Before migrating, a process needs to freeze communication, handle pending messages in the receive buffer and pack checkpoint data. Besides the usual merits of concurrency, location transparency and the absence of residual dependency, our scheme solves the incoming message problem at the application level and is portable and easy to use in a heterogeneous environment. Our experiment shows that our facility can help to utilize 74% of idle CPU cycles of a network of workstations with less than 6% overhead on their normal operations.