Enhancing Entropy Throttling: New Classes of Injection Control in Interconnection Networks

Abstract

SUMMARYState-of-the-art parallel computers, which are growing in parallelism, require a lot of things in their interconnection networks. Although wide spectrum of efforts in research and development for effective and practical interconnection networks are reported, the problem is still open. One of the largest issues is congestion control that intends to maximize the network performance in terms of throughput and latency. Throttling, or injection limitation, is one of the center ideas of congestion control. We have proposed a new class of throttling method, Entropy Throttling, whose foundation is entropy concept of packets. The throttling method is successful in part, however, its potentials are not sufficiently discussed. This paper aims at exploiting capabilities of the Entropy Throttling method via comprehensive evaluation. Major contributions of this paper are to introduce two ideas of hysteresis function and guard time and also to clarify wide performance characteristics in steady and unsteady communication situations. By introducing the new ideas, we extend the Entropy throttling method. The extended methods improve communication performance at most 3.17 times in the best case and 1.47 times in average compared with non-throttling cases in collective communication, while the method can sustain steady communication performance.

A Static Packet Scheduling Approach for Fast Collective Communication by Using PSO

“…Literature [3], [6]- [8] shows representative methods and the authors have also proposed effective throttling methods [4], [5], [9]. The dynamic control solutions are effective in stable situations of communication, however, they do not guarantee optimal behaviors in unsteady communications.…”

“…Literature [4], [5] suggests that appropriate intervals between injection of packets possibly increase performance. It is a natural consequence since consecutive (i.e., zerodelay) packet injection causes unnecessary congestion.…”

“…For comparison purpose, we use our dynamic control method named Entropy Throttling [4], [5]. This method suspends packet injection (i.e., throttling), when the network detects congested situation.…”