On scalability for MPI runtime systems

The future of high performance computing, as being currently foretold, will gravitate toward hundreds of thousands to million node machines, harnessing the computing power of billions of cores. While the hardware part is well covered, the software infrastructure at that scale is vague. However, no matter what the infrastructure will be, efficiently running parallel applications on such large machines will require optimized runtime environments that are scalable and resilient. More particularly, considering a future where Message Passing Interface (MPI) remains a major programming paradigm, the MPI implementations will have to seamlessly adapt to launching and managing large scale applications on resources several levels of magnitude larger than today. In this paper, we present a modified version of the Open MPI runtime that has been adapted towards a scalability goal. We evaluate the performance and compare it with two widely used runtime systems: the default version of Open MPI and MPICH2; using various underlying launching systems. The performance evaluation demonstrates a significant improvement over the state of the art. We also discuss the basic requirements for an exascale-ready parallel runtime.