.\" Copyright (c) 2007-2008 Joseph Koshy.  All rights reserved.
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.\" $FreeBSD$
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.Dd September 22, 2008
.Dt PMC_ENABLE 3
.Os
.Sh NAME
.Nm pmc_disable ,
.Nm pmc_enable
.Nd administrative control of hardware performance counters
.Sh LIBRARY
.Lb libpmc
.Sh SYNOPSIS
.In pmc.h
.Ft int
.Fn pmc_disable "int cpu" "int pmc"
.Ft int
.Fn pmc_enable "int cpu" "int pmc"
.Sh DESCRIPTION
These functions allow specific hardware performance monitoring
counters in a system to be disabled and enabled administratively.
The hardware performance counters available on each CPU are numbered
using small non-negative integers, in a system dependent manner.
Disabled counters will not be available to applications for use.
.Pp
The invoking process needs to have the
.Dv PRIV_PMC_MANAGE
privilege to perform these operations.
.Pp
Function
.Fn pmc_disable
disables the hardware counter numbered by argument
.Fa pmc
on CPU number
.Fa cpu .
.Pp
Function
.Fn pmc_enable
enables the hardware counter numbered by argument
.Fa pmc
on CPU number
.Fa cpu .
.Sh IMPLEMENTATION NOTES
Hardware PMCs that are currently in use by applications cannot be
disabled.
Allocation of a process scope software PMC marks all
hardware PMCs in the system with the same pmc number as being in-use.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
A call to these functions may fail with the following errors:
.Bl -tag -width Er
.It Bq Er EBUSY
Function
.Fn pmc_disable
specified a hardware PMC is currently in use.
.It Bq Er EINVAL
Arguments
.Fa cpu
or
.Fa pmc
were invalid.
.It Bq Er ENXIO
Argument
.Fa cpu
specified a disabled or absent CPU.
.It Bq Er EPERM
The current process lacks sufficient privilege to perform this
operation.
.El
.Sh SEE ALSO
.Xr pmc 3 ,
.Xr pmc_cpuinfo 3 ,
.Xr pmc_pmcinfo 3 ,
.Xr hwpmc 4 ,
.Xr pmccontrol 8 ,
.Xr priv_check 9