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$FreeBSD: head/lib/libpmc/pmc_read.3 196441 2009-08-23 06:22:31Z jkoshy $
.Dd November 25, 2007 .Os .Dt PMC_READ 3 .Sh NAME .Nm pmc_read , .Nm pmc_rw , .Nm pmc_write , .Nd read and write hardware performance counters .Sh LIBRARY .Lb libpmc .Sh SYNOPSIS n pmc.h .Ft int .Fn pmc_read "pmc_id_t pmc" "pmc_value_t *value" .Ft int .Fn pmc_rw "pmc_id_t pmc" "pmc_value_t newvalue" "pmc_value_t *oldvaluep" .Ft int .Fn pmc_write "pmc_id_t pmc" "pmc_value_t value" .Sh DESCRIPTION These functions read and write the current value of a PMC.
p Function .Fn pmc_read with read the current value of the PMC specified by argument .Fa pmc and write it to the location specified by argument .Fa value .
p Function .Fn pmc_write will set the current value of the PMC specified by argument .Fa pmc to the value specified by argument .Fa value .
p Function .Fn pmc_rw combines a read and a write into a single atomic operation.
p For write operations the PMC should be a quiescent state. .Sh RETURN VALUES .Rv -std .Sh ERRORS A call to these functions may fail with the following errors: l -tag -width Er t Bq Er EBUSY A write operation specified a currently running PMC. t Bq Er EINVAL Argument .Fa pmc specified a PMC not in a readable state. t Bq Er EINVAL The PMC specified by argument .Fa pmc was not owned by the current process. .El .Sh SEE ALSO .Xr pmc 3 , .Xr hwpmc 4