基于计数器的处理器核性能分析与优化

随着处理器微体系结构日益复杂,性能分析在处理器研制过程中的作用越来越重要。常用的性能分析方法是建立性能模型,该方法主要用于研制初期的设计空间探索,如果用于微体系结构级的分析和优化,速度和精度都会成为限制因素。提出了一种基于计数器的性能分析方法,该方法以项目组已经完成的一款处理器核的硬件实现代码为基础,在处理器核外部添加一个专用性能监测单元,收集微体系结构分析和优化需要的各种事件,并通过结果分析器对统计的事件进行分析,得到微体系结构实现的性能受限因素。采用此方法,在FPGA原型系统上对SPEC CPU2000测试程序运行时的性能受限因素进行了分析,并根据分析结果采取了相应的优化措施,优化后的处理器核性能得到了明显提升。

Counters Based Performance Analysis and Optimization of a Processor Core

With the ever-increasing design complexity in the processor microarchitecture, performance analysis becomes more and more important in the research and design of processors. Performance models are used widely in the performance analysis, which are more suitable for the design space exploration in the early stage. When being used in microarchitecture optimizations, the accuracy and speed of performance models are the limiting factors. In this paper, a performance analysis method based on counters is proposed. In this method, the RTL code of an processor core is used as a baseline, and a specialized performance monitor unit is added to collect the events needed by the microarchitecture analysis and optimization. Then the collected events are sent to a result analyzer, where the factors affecting the performance are obtained. Adopting the method, we analyze what affect the performance when running SPEC CPU2000 benchmarks on FPGA prototyping, and optimize the microarchitecture of processor core according to the analysis results. The performance of the optimized processor core is improved obviously.