For the majority of the APIs it is necessary that the Performance Inspector device driver be loaded.
Examples include information about the number of active and installed processors, processor word size, processor architecture, type of processor, etc.
Examples include initializing/terminating the SWTRACE facility, enabling/disabling trace major codes, turning tracing on and off, writing trace hooks, etc.
Examples include reading/writing any MSR, accessing the hardware performance counters and their control registers, and accessing performance counter events. Events are specific performance counter configurations managed by the tools.