Analysing the Fidelity of Measurements Performed with Hardware Performance Counters

摘要

Performance evaluation requires accurate and dependable measurements of timing values. Such measurements are usually made using timer methods, but these methods are often too coarse-grained and too inaccurate. Thus, direct usage of hardware performance counters is frequently used for fine-granular measurements due to higher accuracy. However, direct access to these counters may be misleading on mul-ticore computers because cores can be paused or core affinity changed by the operating system, resulting in misleading counter values. The contribution of this paper is the demonstration of an additional, significant flaw arising from the direct use of hardware performance counters. We demonstrate that using JNI and assembler instructions to access the Timestamp Counter from Java applications can result in grossly wrong values, even in single-threaded scenarios.