CART: Cache Access Reordering Tree for Efficient Cache and Memory Accesses in GPUs

Graphics processing units (GPUs) have been increasingly used to accelerate general purpose computing. Thousands of concurrently running threads in a GPU demand a highly efficient memory subsystem for data supply. A key factor that affects the memory subsystem is the order of memory accesses. While reordering memory accesses at L2 cache has large potential benefits to both cache and DRAM, little work has been conducted to exploit this. In this paper, we investigate the largely unexplored opportunity of L2 cache access reordering. We propose Cache Access Reordering Tree (CART), a novel architecture that can improve memory subsystem efficiency by actively reordering memory accesses at L2 cache to be cache-friendly and DRAM-friendly. Evaluation results using a wide range of benchmarks show that, the proposed CART is able to improve the average IPC of memory intensive benchmarks by 34.2% with only 1.7% area overhead.