Techniques for Shared Resource Management in Systems with Throughput Processors

The continued growth of the computational capability of throughput processors has made throughput processors the platform of choice for a wide variety of high performance computing applications. Graphics Processing Units (GPUs) are a prime example of throughput processors that can deliver high performance for applications ranging from typical graphics applications to general-purpose data parallel (GPGPU) applications. However, this success has been accompanied by new performance bottlenecks throughout the memory hierarchy of GPU-based systems. This dissertation identifies and eliminates performance bottlenecks caused by major sources of interference throughout the memory hierarchy. Specifically, we provide an in-depth analysis of interand intra-application as well as interaddress-space interference that significantly degrade the performance and efficiency of GPU-based systems. To minimize such interference, we introduce changes to the memory hierarchy for systems with GPUs that allow the memory hierarchy to be aware of both CPU and GPU applications’ characteristics. We introduce mechanisms to dynamically analyze different applications’ characteristics and propose four major changes throughout the memory hierarchy. First, we introduce Memory Divergence Correction (MeDiC), a cache management mechanism that mitigates intra-application interference in GPGPU applications by allowing the shared L2 cache and the memory controller to be aware of the GPU’s warp-level memory divergence characteristics. MeDiC uses this warp-level memory divergence information to give more cache space and more memory bandwidth to warps that benefit most from utilizing such resources. Our evaluations show that MeDiC significantly outperforms multiple state-of-the-art caching policies proposed for GPUs. Second, we introduce the Staged Memory Scheduler (SMS), an application-aware CPU-GPU memory request scheduler that mitigates inter-application interference in heterogeneous CPU-GPU systems. SMS creates a fundamentally new approach to memory controller design that decouples the memory controller into three significantly simpler structures, each of which has a separate task, These structures operate together to greatly improve both system performance and fairness. Our three-stage memory controller first groups requests based on row-buffer locality. This grouping allows the second stage to focus on inter-application scheduling decisions. These two stages enforce high-level policies regarding performance and fairness. As a result, the last stage is simple logic that deals only with the low-level DRAM commands and timing. SMS is also configurable: it allows the system software to trade off between the quality of service provided to the CPU versus GPU applications. Our evaluations show that SMS not only reduces inter-application interference caused by the GPU, thereby improving heterogeneous system performance, but also provides better scalability and power efficiency compared to multiple state-of-the-art memory schedulers.