ViPZonE: Hardware Power Variability-Aware Virtual Memory Management for Energy Savings

Abstract—Hardware variability is predicted to increase dramatically over the coming years as a consequence of continued technology scaling. In this paper, we apply the Underdesigned and Opportunistic Computing (UnO) paradigm by exposing system-level power variability to software to improve energy efficiency. We present ViPZonE, a memory management solution in conjunction with application annotations that opportunistically performs memory allocations to reduce DRAM energy. ViPZonE’s components consist of a physical address space with DIMM-aware zones, a modified page allocation routine, and a new virtual memory system call for dynamic allocations from userspace. We implemented ViPZonE in the Linux kernel with GLIBC API support, running on a real x86-64 testbed with significant access power variation in its DDR3 DIMMs. We demonstrate that on our testbed, ViPZonE can save up to 27.80% memory energy, with no more than 4.80 % performance degradation across a set of PARSEC benchmarks tested with respect to the baseline Linux software. Furthermore, through a hypothetical “what-if ” extension, we predict that in future non-volatile memory systems which consume almost no idle power, ViPZonE could yield even greater benefits, demonstrating the ability to exploit memory hardware variability through opportunistic software. Index Terms—DRAM, variability, energy-aware systems, main memory, allocation/deallocation strategies, operating systems F