.\" Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
.\" and Copyright (C) 2013 Michael Kerrisk <mtk.manpages@gmail.com>
.\" Written by Ivana Varekova <varekova@redhat.com>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH perfmonctl 2 2023-03-30 "Linux man-pages 6.05.01"
.SH NAME
perfmonctl \- interface to IA-64 performance monitoring unit
.SH SYNOPSIS
.nf
.B #include <syscall.h>
.B #include <perfmon.h>
.PP
.BI "long perfmonctl(int " fd ", int " cmd ", void " arg [. narg "], int " narg ");"
.fi
.PP
.IR Note :
There is no glibc wrapper for this system call; see HISTORY.
.SH DESCRIPTION
The IA-64-specific
.BR perfmonctl ()
system call provides an interface to the
PMU (performance monitoring unit).
The PMU consists of PMD (performance monitoring data) registers and
PMC (performance monitoring control) registers,
which gather hardware statistics.
.PP
.BR perfmonctl ()
applies the operation
.I cmd
to the input arguments specified by
.IR arg .
The number of arguments is defined by \fInarg\fR.
The
.I fd
argument specifies the perfmon context to operate on.
.PP
Supported values for
.I cmd
are:
.TP
.B PFM_CREATE_CONTEXT
.nf
.BI  "perfmonctl(int " fd ", PFM_CREATE_CONTEXT, pfarg_context_t *" ctxt ", 1);"
.fi
Set up a context.
.IP
The
.I fd
parameter is ignored.
A new perfmon context is created as specified in
.I ctxt
and its file descriptor is returned in \fIctxt\->ctx_fd\fR.
.IP
The file descriptor can be used in subsequent calls to
.BR perfmonctl ()
and can be used to read event notifications (type
.IR pfm_msg_t )
using
.BR read (2).
The file descriptor is pollable using
.BR select (2),
.BR poll (2),
and
.BR epoll (7).
.IP
The context can be destroyed by calling
.BR close (2)
on the file descriptor.
.TP
.B PFM_WRITE_PMCS
.\" pfm_write_pmcs()
.nf
.BI  "perfmonctl(int " fd ", PFM_WRITE_PMCS, pfarg_reg_t *" pmcs ", n);"
.fi
Set PMC registers.
.TP
.B PFM_WRITE_PMDS
.nf
.BI  "perfmonctl(int " fd ", PFM_WRITE_PMDS, pfarg_reg_t *" pmds ", n);"
.fi
.\" pfm_write_pmds()
Set PMD registers.
.TP
.B PFM_READ_PMDS
.\" pfm_read_pmds()
.nf
.BI  "perfmonctl(int " fd ", PFM_READ_PMDS, pfarg_reg_t *" pmds ", n);"
.fi
Read PMD registers.
.TP
.B PFM_START
.\" pfm_start()
.nf
.\" .BI  "perfmonctl(int " fd ", PFM_START, arg, 1);
.BI  "perfmonctl(int " fd ", PFM_START, NULL, 0);"
.fi
Start monitoring.
.TP
.B PFM_STOP
.\" pfm_stop()
.nf
.BI  "perfmonctl(int " fd ", PFM_STOP, NULL, 0);"
.fi
Stop monitoring.
.TP
.B PFM_LOAD_CONTEXT
.\" pfm_context_load()
.nf
.BI  "perfmonctl(int " fd ", PFM_LOAD_CONTEXT, pfarg_load_t *" largs ", 1);"
.fi
Attach the context to a thread.
.TP
.B PFM_UNLOAD_CONTEXT
.\" pfm_context_unload()
.nf
.BI  "perfmonctl(int " fd ", PFM_UNLOAD_CONTEXT, NULL, 0);"
.fi
Detach the context from a thread.
.TP
.B PFM_RESTART
.\" pfm_restart()
.nf
.BI  "perfmonctl(int " fd ", PFM_RESTART, NULL, 0);"
.fi
Restart monitoring after receiving an overflow notification.
.TP
.B PFM_GET_FEATURES
.\" pfm_get_features()
.nf
.BI  "perfmonctl(int " fd ", PFM_GET_FEATURES, pfarg_features_t *" arg ", 1);"
.fi
.TP
.B PFM_DEBUG
.\" pfm_debug()
.nf
.BI  "perfmonctl(int " fd ", PFM_DEBUG, " val ", 0);"
.fi
If
.I val
is nonzero, enable debugging mode, otherwise disable.
.TP
.B PFM_GET_PMC_RESET_VAL
.\" pfm_get_pmc_reset()
.nf
.BI  "perfmonctl(int " fd ", PFM_GET_PMC_RESET_VAL, pfarg_reg_t *" req  ", n);"
.fi
Reset PMC registers to default values.
.\"
.\"
.\" .TP
.\" .B PFM_CREATE_EVTSETS
.\"
.\" create or modify event sets
.\" .nf
.\" .BI  "perfmonctl(int " fd ", PFM_CREATE_EVTSETS, pfarg_setdesc_t *desc , n);
.\" .fi
.\" .TP
.\" .B PFM_DELETE_EVTSETS
.\" delete event sets
.\" .nf
.\" .BI  "perfmonctl(int " fd ", PFM_DELETE_EVTSET, pfarg_setdesc_t *desc , n);
.\" .fi
.\" .TP
.\" .B PFM_GETINFO_EVTSETS
.\" get information about event sets
.\" .nf
.\" .BI  "perfmonctl(int " fd ", PFM_GETINFO_EVTSETS, pfarg_setinfo_t *info, n);
.\" .fi
.SH RETURN VALUE
.BR perfmonctl ()
returns zero when the operation is successful.
On error, \-1 is returned and
.I errno
is set to indicate the error.
.SH STANDARDS
Linux on IA-64.
.SH HISTORY
Added in Linux 2.4;
.\" commit ecf5b72d5f66af843f189dfe9ce31598c3e48ad7
removed in Linux 5.10.
.PP
This system call was broken for many years,
and ultimately removed in Linux 5.10.
.PP
glibc does not provide a wrapper for this system call;
on kernels where it exists, call it using
.BR syscall (2).
.SH SEE ALSO
.BR gprof (1)
.PP
The perfmon2 interface specification