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50f6c13997
This was added in b2ca2e50b9, and serves to provide an initial value
to the PMC, eliminating the need for a second syscall via pmc_set(3).
Reviewed by: gnn, 0mp (manpages)
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D29885
200 lines
5.4 KiB
Groff
200 lines
5.4 KiB
Groff
.\" Copyright (c) 2007-2008 Joseph Koshy. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd April 21, 2021
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.Dt PMC_ALLOCATE 3
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.Os
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.Sh NAME
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.Nm pmc_allocate ,
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.Nm pmc_release
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.Nd allocate and free performance monitoring counters
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.Sh LIBRARY
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.Lb libpmc
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.Sh SYNOPSIS
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.In pmc.h
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.Ft int
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.Fo pmc_allocate
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.Fa "const char *eventspecifier"
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.Fa "enum pmc_mode mode"
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.Fa "uint32_t flags"
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.Fa "int cpu"
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.Fa "pmc_id_t *pmcid"
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.Fa "uint64_t count"
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.Fc
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.Ft int
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.Fn pmc_release "pmc_id_t pmc"
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.Sh DESCRIPTION
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Function
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.Fn pmc_allocate
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allocates a performance monitoring counter that measures the events
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named by argument
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.Fa eventspecifier ,
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and writes the allocated handle to the location pointed to by argument
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.Fa pmcid .
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.Pp
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Argument
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.Fa eventspecifier
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comprises an PMC event name followed by an optional comma separated
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list of keywords and qualifiers.
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The allowed syntax for argument
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.Fa eventspecifier
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is processor specific and is listed in section
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.Sx "EVENT SPECIFIERS"
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in the
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.Xr pmc 3
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manual page.
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.Pp
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The desired PMC mode is specified by argument
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.Fa mode .
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Legal values for the
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.Fa mode
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argument are:
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.Bl -tag -width ".Dv PMC_MODE_SS" -compact
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.It Dv PMC_MODE_SC
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Allocate a system-scope counting PMC.
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.It Dv PMC_MODE_SS
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Allocate a system-scope sampling PMC.
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.It Dv PMC_MODE_TC
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Allocate a process-scope counting PMC.
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.It Dv PMC_MODE_TS
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Allocate a process-scope sampling PMC.
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.El
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.Pp
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Mode specific modifiers may be specified using argument
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.Fa flags .
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The flags supported at PMC allocation time are:
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.Bl -tag -width ".Dv PMC_F_LOG_PROCEXIT" -compact
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.It Dv PMC_F_DESCENDANTS
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For process-scope PMCs, automatically track descendants of attached
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processes.
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.It Dv PMC_F_LOG_PROCCSW
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For process-scope counting PMCs, generate a log event at every context
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switch containing the incremental number of hardware events seen
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by the process during the time it was executing on the CPU.
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.It Dv PMC_F_LOG_PROCEXIT
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For process-scope counting PMCs, accumulate hardware events seen
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when the process was executing on a CPU and generate a log event
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when an attached process exits.
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.El
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PMCs allocated with flags
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.Dv PMC_F_LOG_PROCCSW
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and
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.Dv PMC_F_LOG_PROCEXIT
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need a log file to be configured before they are started.
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.Pp
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For system scope PMCs, the argument
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.Fa cpu
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is a non-negative value that specifies the CPU number
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that the PMC is to be allocated on.
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Process scope PMC allocations should specify the constant
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.Dv PMC_CPU_ANY
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for this argument.
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.Pp
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The
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.Fa count
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argument behaves identically to the
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.Xr pmc_set 3
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function's
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.Fa value
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argument.
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For counting PMCs,
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.Fa count
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specifies the initial value of the allocated PMC.
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For sampling PMCs,
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.Fa count
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specifies the reload count.
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.Pp
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Function
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.Fn pmc_release
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releases the PMC denoted by argument
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.Fa pmcid .
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.Sh RETURN VALUES
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If successful, function
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.Fn pmc_allocate
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sets the location specified by argument
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.Fa pmcid
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to the handle of the allocated PMC and returns 0.
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In case of an error, the function returns -1 and sets the global
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variable
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.Va errno
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to indicate the error.
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.Pp
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.Rv -std pmc_release
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The argument
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.Fa mode
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to function
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.Fn pmc_allocate
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had an invalid value.
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.It Bq Er EINVAL
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Argument
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.Fa cpu
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to function
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.Fn pmc_allocate
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had an invalid CPU number.
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.It Bq Er EINVAL
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Argument
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.Fa flags
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contained flags that were unsupported or otherwise incompatible with
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the requested PMC mode.
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.It Bq Er EINVAL
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Argument
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.Fa eventspecifier
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to function
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.Fn pmc_allocate
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specified an event not supported by hardware or contained a syntax
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error.
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.It Bq Er ENXIO
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Function
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.Fn pmc_allocate
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requested the use of a hardware resource that was absent or
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administratively disabled.
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.It Bq Er EOPNOTSUPP
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The underlying hardware does not support the capabilities needed for
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a PMC being allocated by a call to
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.Fn pmc_allocate .
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.It Bq Er EPERM
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A system scope PMC allocation was attempted without adequate process
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privilege.
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.It Bq Er ESRCH
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Function
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.Fn pmc_release
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was called without first having allocated a PMC.
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.It Bq Er EINVAL
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Argument
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.Fa pmcid
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to function
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.Fn pmc_release
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did not specify a PMC previously allocated by this process.
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.El
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.Sh SEE ALSO
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.Xr pmc 3 ,
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.Xr pmc_attach 3 ,
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.Xr pmc_configure_logfile 3 ,
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.Xr pmc_start 3 ,
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.Xr hwpmc 4
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