NAME

pmc_read, pmc_rw, pmc_write — read and write hardware performance counters

LIBRARY

Performance Counters Library (libpmc, -lpmc)

#include <pmc.h>

int
pmc_read(pmc_id_t pmc, pmc_value_t *value);

int
pmc_rw(pmc_id_t pmc, pmc_value_t newvalue, pmc_value_t *oldvaluep);

int
pmc_write(pmc_id_t pmc, pmc_value_t value);

These functions read and write the current value of a PMC.

Function pmc_read() will read the current value of the PMC specified by argument pmc and write it to the location specified by argument value.

Function pmc_write() will set the current value of the PMC specified by argument pmc to the value specified by argument value.

Function pmc_rw() combines a read and a write into a single atomic operation.

For write operations the PMC should be a quiescent state.

Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

A call to these functions may fail with the following errors:

[EBUSY]: A write operation specified a currently running PMC.
[EINVAL]: Argument pmc specified a PMC not in a readable state.
[EINVAL]: The PMC specified by argument pmc was not owned by the current process.