Hardware Performance Counters

Most modern CPUs have built-in performance counters. Each CPU design measures and counts metrics corresponding to its architecture. Several research groups have attempted to make portable interfaces for the hardware performance counters across the wide range of CPU architectures.

• One of the best known is PAPI: A Portable Interface to Hardware Performance Counters.
• Another interface, Rabbit, is available for Intel or AMD CPUs.

Both provide access to performance counter data from the CPU. Such low-level packages require interaction with the kernel; they are extensions to its basic functionality. In order to use any of the C library interfaces, either support must be compiled directly into the kernel, or a special hardware performance counter module must be built and loaded. Beowulf builders are encouraged to immediately extend their operating system with support for hardware performance counters.