sentences:  Operating system support for accessing hardware counters is needed to use PAPI.For example, prior to 2010, a Linux/x86 kernel had to be patched with a performance monitoring counters driver (perfctr link) to support PAPI.Since Linux version 2.6.32, and PAPI 2010 releases, PAPI can leverage the existing perf subsystem in Linux, and thus does not need any out of tree driver to be functional anymore.