GWalloc: A self-adaptive generational wear-aware allocator for non-volatile main memory

Phase Change Memory (PCM) is considered a promising replacement for DRAM due to its superior performance characteristics such as low leakage power, high integration density, byte addressability and non-volatility. However, PCM's limited write endurance significantly hinders its wide application. For example, PCM wears out quickly with traditional dynamic memory allocation policy in embedded systems which aggregates lots of writes in few memory blocks. To extend the lifespan of PCM, some wear-aware dynamic memory allocators have been proposed, which generally depend on some fixed parameters to limit the wear of PCM. However, these allocators can be inflexible as it is difficult to specify appropriate values for the required parameters in different scenarios. In this paper, we propose a Self-Adaptive Generational Wear-Aware Allocator (GWalloc). GWalloc divides memory blocks into two generations: the young and the old generation, according to their number of allocation times. GWalloc also dynamically adjusts the system's wear threshold during allocations so that it can effectively balance the wear degree of PCM and the consumed memory space. The wear threshold restricts the upper wear limit of young memory blocks. Experimental evaluations show that compared with the state-of-the-art wear-aware dynamic memory allocators (NVMalloc, Walloc and UWLalloc), GWalloc improves PCM wear-leveling (evaluated by CV, a wear leveling indicator) by 38.6%, 39.1% and 38.3%, and saves 62.1%, 22.2% and 37.2% memory space overhead.