Switching Optically-Connected Memories in a Large-Scale System

Recent trends in processor and memory systems in large-scale computing systems reveal a new "memory wall" that prompts investigation on alternate main memory organization separating main memory from processors and arranging them in separate ensembles. In this paper, we study the feasibility of transferring data across processors by using the optical interconnection fabric that acts as a bridge between processor and memory ensembles. We propose a memory switching protocol that transfers data across processors without physically moving the data across electrical switches. Such a mechanism allows large-scale data communication across processors through transfer of a few tiny blocks of meta-data. We present detailed techniques for supporting two communication patterns prevalent in any large-scale scientific and data management applications. We present experimental results analyzing the feasibility of memory switching in a wide range of applications, and characterize applications based on the impact of the memory switching on their performance.