Non-intrusive Migration of MPI Processes in OS-Bypass Networks

Load balancing, maintenance, and energy efficiency are key challenges for upcoming supercomputers. An indispensable tool for the accomplishment of these tasks is the ability to migrate applications during runtime. Especially in HPC, where any performance hit is frowned upon, such migration mechanisms have to come with minimal overhead. This constraint is usually not met by current practice adding further abstraction layers to the software stack. In this paper, we propose a concept for the migration of MPI processes communicating over OS-bypass networks such as InfiniBand. While being transparent to the application, our solution minimizes the runtime overhead by introducing a protocol for the shutdown of individual connections prior to the migration. It is implemented on the basis of an MPI library and evaluated using virtual machines based on KVM. Our evaluation reveals that the runtime overhead is negligible small. The migration time itself is mainly determined by the particular migration mechanism, whereas the additional execution time of the presented protocol converges to 2ms per connection if more than a few dozen connections are shut down at a time.