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33 .Nd read and write hardware performance counters
39 .Fn pmc_read "pmc_id_t pmc" "pmc_value_t *value"
41 .Fn pmc_rw "pmc_id_t pmc" "pmc_value_t newvalue" "pmc_value_t *oldvaluep"
43 .Fn pmc_write "pmc_id_t pmc" "pmc_value_t value"
45 These functions read and write the current value of a PMC.
49 with read the current value of the PMC specified by argument
51 and write it to the location specified by argument
56 will set the current value of the PMC specified by argument
58 to the value specified by argument
63 combines a read and a write into a single atomic operation.
65 For write operations the PMC should be a quiescent state.
69 A call to these functions may fail with the following errors:
72 A write operation specified a currently running PMC.
76 specified a PMC not in a readable state.
78 The PMC specified by argument
80 was not owned by the current process.