An enhancer of memory and network for applications with large-capacity data and non-continuous data accessing

摘要

The performance of memory and I/O systems is insufficient to catch up with that of COTS (Commercial Off-The-Shelf) CPU. PC clusters using COTS CPU have been employed for HPC. A cache-based processor is far less effective than a vector processor in applications with low spatial locality. Moreover, for HPC, Google-like server farms and database processing, insufficient capacity of main memory poses a serious problem. Power consumption of a Google-like server farm or a high-end HPC PC cluster is huge. In order to overcome these problems, we propose a concept of a memory and network enhancer equipped with scatter and gather vector access functions, high-performance network connectivity, and capacity extensibility. Communication mechanisms named LHS and LHC are also proposed. LHS and LHC are architectures for reducing latency for mixed messages with small controlling data and large data body. Examples of the killer applications of this new type of hardware are presented. This paper presents not only concepts and simulations but also real hardware prototypes named DIMMnet-2 and DIMMnet-3. This paper presents the evaluations concerning memory issues and network issues. We evaluate the module with NAS CG benchmark class C and Wisconsin benchmarks as applications with memory issues. Although evaluation for CG class C is difficult with conventional cycle-accurate simulation methods, we obtained the result for class C with our original method. As a result, we find that the module can improve its maximum performance about 25 times more with Wisconsin benchmarks. However, the results on a cache-based PC show the cache-line flushing degrades acceleration ratio. This shows the high potential of the proposed extended memory module and processors in combination with DMA-based main memory access such as SPU on Cell/B.E. that does not need cache-line flushing. The LHS and LHC communication mechanisms are evaluated in this paper. The evaluations of their effects on latency are shown.