Exploring cache bypassing and partitioning for multi-tasking on GPUs.

Graphics Processing Units (GPUs) computing has become ubiquitous for embedded system, evidenced by its wide adoption for various general purpose applications. As more and more applications are accelerated by GPUs, multi-tasking scenario starts to emerge. Multi-tasking allows multiple applications to simultaneously execute on the same GPU and share the resource. This brings new challenges due to the contention among the different applications for the shared resources such as caches. However, the caches on GPUs are difficult to use. If used inappropriately, it may hurt the performance instead of improving it. In this paper, we propose to use cache partitioning together with cache bypassing as the shared cache management mechanism for multi-tasking on GPUs. The combined approach aims to reduce the interference among the tasks and preserve the locality for each task. However, the interplay among the cache partitioning and bypassing brings greater challenges. On one hand, the partitioned cache space to each task affects its cache bypassing decision. On the other hand, cache bypassing affects the cache capacity required for each task. To address this, we propose a two-step approach. First, we use cache partitioning to assign dedicated cache space to each task to reduce the interference among the tasks. During this process, we compare cache partitioning with coarse-grained cache bypassing. Then, we use fine-grained cache bypassing to selectively bypass certain data requests and threads for each task. We explore different cache partitioning and bypassing designs and demonstrate the potential benefits of this approach. Experiments using a wide range of applications demonstrate that our technique improves the overall system throughput by 52% on average compared to the default multi-tasking solution on GPUs.