Using multiple streams can improve the overall system performance by mitigating the data transfer overhead on heterogeneous systems. Currently, very few cases have been streamed to demonstrate the streaming performance impact and a systematic investigation of streaming necessity and how-to over a large number of test cases remains a gap. In this paper, we use a total of 56 benchmarks to build a statistical view of the data transfer overhead, and give an in-depth analysis of the impacting factors. Among the heterogeneous codes, we identify two types of non-streamable codes and three types of streamable codes, for which a streaming approach has been proposed. Our experimental results on the CPU-MIC platform show that, with multiple streams, we can improve the application performance by up 90 . Our work can serve as a generic flow of using multiple streams on heterogeneous platforms.
@cite_11: As both CPUs and GPUs become employed in a wide range of applications, it has been acknowledged that both of these Processing Units (PUs) have their unique features and strengths and hence, CPU-GPU collaboration is inevitable to achieve high-performance computing. This has motivated a significant amount of research on heterogeneous computing techniques, along with the design of CPU-GPU fused chips and petascale heterogeneous supercomputers. In this article, we survey Heterogeneous Computing Techniques (HCTs) such as workload partitioning that enable utilizing both CPUs and GPUs to improve performance and or energy efficiency. We review heterogeneous computing approaches at runtime, algorithm, programming, compiler, and application levels. Further, we review both discrete and fused CPU-GPU systems and discuss benchmark suites designed for evaluating Heterogeneous Computing Systems (HCSs). We believe that this article will provide insights into the workings and scope of applications of HCTs to researchers and motivate them to further harness the computational powers of CPUs and GPUs to achieve the goal of exascale performance.
@cite_8: Developing highly scalable algorithms for global atmospheric modeling is becoming increasingly important as scientists inquire to understand behaviors of the global atmosphere at extreme scales. Nowadays, heterogeneous architecture based on both processors and accelerators is becoming an important solution for large-scale computing. However, large-scale simulation of the global atmosphere brings a severe challenge to the development of highly scalable algorithms that fit well into state-of-the-art heterogeneous systems. Although successes have been made on GPU-accelerated computing in some top-level applications, studies on fully exploiting heterogeneous architectures in global atmospheric modeling are still very less to be seen, due in large part to both the computational difficulties of the mathematical models and the requirement of high accuracy for long term simulations. In this paper, we propose a peta-scalable hybrid algorithm that is successfully applied in a cubed-sphere shallow-water model in global atmospheric simulations. We employ an adjustable partition between CPUs and GPUs to achieve a balanced utilization of the entire hybrid system, and present a pipe-flow scheme to conduct conflict-free inter-node communication on the cubed-sphere geometry and to maximize communication-computation overlap. Systematic optimizations for multithreading on both GPU and CPU sides are performed to enhance computing throughput and improve memory efficiency. Our experiments demonstrate nearly ideal strong and weak scalabilities on up to 3,750 nodes of the Tianhe-1A. The largest run sustains a performance of 0.8 Pflops in double precision (32 of the peak performance), using 45,000 CPU cores and 3,750 GPUs.
@cite_16: In this paper, we describe our experiment developing an implementation of the Linpack benchmark for TianHe-1, a petascale CPU GPU supercomputer system, the largest GPU-accelerated system ever attempted before. An adaptive optimization framework is presented to balance the workload distribution across the GPUs and CPUs with the negligible runtime overhead, resulting in the better performance than the static or the training partitioning methods. The CPU-GPU communication overhead is effectively hidden by a software pipelining technique, which is particularly useful for large memory-bound applications. Combined with other traditional optimizations, the Linpack we optimized using the adaptive optimization framework achieved 196.7 GFLOPS on a single compute element of TianHe-1. This result is 70.1 of the peak compute capability and 3.3 times faster than the result using the vendor’s library. On the full configuration of TianHe-1 our optimizations resulted in a Linpack performance of 0.563PFLOPS, which made TianHe-1 the 5th fastest supercomputer on the Top500 list released in November 2009.
@cite_13: A commodity personal computer (PC) can be seen as a hybrid computing system equipped with two different kinds of processors, i.e. CPU and a graphics processing unit (GPU). Since the superiorities of GPUs in the performance and the power efficiency strongly depend on the system configuration and the data size determined at the runtime, a programmer cannot always know which processor should be used to execute a certain kernel. Therefore, this paper presents a runtime environment that dynamically selects an appropriate processor so as to improve the energy efficiency. The evaluation results clearly indicate that the runtime processor selection at executing each kernel with given data streams is promising for energy-aware computing on a hybrid computing system.
@cite_17: We present a runtime framework for the execution of work-loads represented as parallel-operator directed acyclic graphs (PO-DAGs) on heterogeneous multi-core platforms. PO-DAGs combine coarse-grained parallelism at the graph level with fine-grained parallelism within each node, lending naturally to exploiting the intra --- and inter-processing element parallelism present in heterogeneous platforms. We identify four important criteria - Suitability, Locality, Availability and Criticality (SLAC) --- and show that all these criteria must be considered by a heterogeneous runtime framework in order to achieve good performance under varying application and platform characteristics. The proposed model driven runtime (MDR) considers all the aforementioned factors, and tradeoffs among them, by utilizing performance models. These performance models are used to drive key run-time decisions such as mapping of tasks to PEs, scheduling of tasks on each PE, and copying data between memory spaces. We discuss the software architecture and implementation of MDR, and evaluate it using several benchmark programs on three different heterogeneous platforms that contain multi-core CPUs and GPUs. The hardware platforms represent server, laptop, and netbook class systems. MDR achieves up to 4.2X speedup (1.5X on average) over the best of CPU-only, GPU-only, round-robin, GPU-first, and utilization-driven schedulers. We also perform a sensitivity analysis that establishes the importance of considering all four SLAC criteria in order to achieve high performance execution in a heterogeneous runtime framework.
There is a large body of workload partitioning techniques, which intelligently partition the workload between a CPU and a coprocessor at the level of algorithm @cite_16 @cite_8 or during program execution @cite_13 @cite_17 . Partitioning workloads aims to use unique architectural strength of processing units and improve resource utilization @cite_11 . In this work, we focus on how to efficiently utilize the coprocessing device with multiple streams. Ultimately, we need to leverage both workload partitioning and multiple streams to minimize the end-to-end execution time.