具有硬體支援之 ARM 架構上效能監控計數器的虛擬化

Abstract

虛擬化技術已經被廣泛的應用在各個領域，包含了在雲端平台上系統虛 擬化服務，也因為如此在虛擬化環境下系統效能的分析和評估的需求也越來 愈重要，為了要找到複雜軟體系統的效能瓶頸，必須要使用可以讀取硬體效 能計數器的分析工具，雖然現在的處理器基本上都具備了硬體效能計數器， 但是在虛擬化環境下，虛擬機器無法直接操作硬體效能計數器，以至於虛擬 化環境下的軟體效能分析和評估相對於原生系統上更加困難。 自從ARM Cortex A15 有了硬體虛擬化支援之後，系統虛擬化技術在 ARM 的架構上提供了全虛擬化支援而且效能方面得到大量的改善，然而ARM 架構下的虛擬機器仍然無法使用硬體效能計數器。 在這篇論文中將會描述硬體效能計數器虛擬化的設計與實作，讓ARM 架構上的虛擬機器可以使用虛擬的硬體效能計數器來量測與評估軟體效能，最後也會比較在虛擬機器和原生環境下，當我們跑微基準測試軟體所讀取到的硬體效能計數器數據的準確性和穩定性。

Virtualization is comprehensively applied in a variety of different domains, including emerging cloud environments that provide full virtualized operation system as a service. The demand for performance analysis and system diagnosis in virtualization environment is increasing. Profiling tools based on hardware performance counters are necessary for performance debugging of complex software system. All modern processors are equipped with hardware performance counters, but virtual machine monitors (VMMs) do not expose them to the guest virtual machines. Therefore, profiling tools commonly used in native environments are not available in virtualized environments, and performance analysis of software running in a virtualized environment is contrastively difficult. With virtualization hardware extension since ARM Cortex A15, system virtualization on ARM architecture supports full virtualization and earns great performance improvement. However, the hardware performance counters are still untouchable to the guest virtual machines on ARM architecture. This thesis describes the design and implementation of hardware performance counters virtualization that is used to access in the guest virtual machines on ARM architecture with hardware virtualization extension. We present experimental results based on microbenchmarks that show the accuracy and usability of the obtained measurements when compared to native execution.