1.\" 2.\" Copyright (c) 1994, Henrik Vestergaard Draboel 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. All advertising materials mentioning features or use of this software 14.\" must display the following acknowledgement: 15.\" This product includes software developed by Henrik Vestergaard Draboel. 16.\" 4. The name of the author may not be used to endorse or promote products 17.\" derived from this software without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" $FreeBSD: src/usr.sbin/rtprio/rtprio.1,v 1.19.2.4 2002/06/21 16:42:31 charnier Exp $ 32.\" 33.Dd July 23, 1994 34.Dt RTPRIO 1 35.Os 36.Sh NAME 37.Nm rtprio , 38.Nm idprio 39.Nd execute, examine or modify a utility's or process's realtime 40or idletime scheduling priority 41.Sh SYNOPSIS 42.Nm [id|rt]prio 43.Nm [id|rt]prio 44.Oo Fl Oc Ns Ar pid 45.Nm [id|rt]prio 46.Ar priority 47.Ar command 48.Op args 49.Nm [id|rt]prio 50.Ar priority 51.Fl Ar pid 52.Nm [id|rt]prio 53.Fl t 54.Ar command 55.Op args 56.Nm [id|rt]prio 57.Fl t 58.Fl Ar pid 59.Sh DESCRIPTION 60The 61.Nm 62utility is used for controlling realtime process scheduling. 63.Pp 64The 65.Nm idprio 66utility is used for controlling idletime process scheduling, and can be called 67with the same options as 68.Nm . 69.Pp 70A process with a realtime priority is not subject to priority 71degradation, and will only be preempted by another process of equal or 72higher realtime priority. 73.Pp 74A process with an idle priority will run only when no other 75process is runnable and then only if its idle priority is equal or 76greater than all other runnable idle priority processes. 77.Pp 78Both 79.Nm 80or 81.Nm idprio 82when called without arguments will return the realtime priority 83of the current process. 84.Pp 85If 86.Nm 87is called with 1 argument, it will return the realtime priority 88of the process with the specified 89.Ar pid . 90.Pp 91If 92.Ar priority 93is specified, the process or program is run at that realtime priority. 94If 95.Fl t 96is specified, the process or program is run as a normal (non-realtime) 97process. 98.Pp 99If 100.Ar -pid 101is specified, the process with the process identifier 102.Ar pid 103will be modified, else if 104.Ar command 105is specified, that program is run with its arguments. 106.Pp 107.Ar Priority 108is an integer between 0 and RTP_PRIO_MAX (usually 31). 0 is the 109highest priority 110.Pp 111.Ar Pid 112of 0 means "the current process". 113.Pp 114Only root is allowed to set realtime or idle priority for a process. 115.Sh EXIT STATUS 116If 117.Nm 118execute a command, the exit value is that of the command executed. 119In all other cases, 120.Nm 121exits 0 on success, and 1 for all other errors. 122.Sh EXAMPLES 123To see which realtime priority the current process is at: 124.Bd -literal -offset indent -compact 125.Sy "rtprio" 126.Ed 127.Pp 128To see which realtime priority of process 129.Em 1423 : 130.Bd -literal -offset indent -compact 131.Sy "rtprio 1423" 132.Ed 133.Pp 134To run 135.Xr cron 8 136at the lowest realtime priority: 137.Bd -literal -offset indent -compact 138.Sy "rtprio 31 cron" 139.Ed 140.Pp 141To change the realtime priority of process 142.Em 1423 143to 144.Em 16 : 145.Bd -literal -offset indent -compact 146.Sy "rtprio 16 -1423" 147.Ed 148.Pp 149To run 150.Xr tcpdump 1 151without realtime priority: 152.Bd -literal -offset indent -compact 153.Sy "rtprio -t tcpdump" 154.Ed 155.Pp 156To change the realtime priority of process 157.Em 1423 158to 159.Dv RTP_PRIO_NORMAL 160(non-realtime/normal priority): 161.Bd -literal -offset indent -compact 162.Sy "rtprio -t -1423" 163.Ed 164.Pp 165To make depend while not disturbing other machine usage: 166.Bd -literal -offset indent -compact 167.Sy "idprio 31 make depend" 168.Ed 169.Sh SEE ALSO 170.Xr nice 1 , 171.Xr ps 1 , 172.Xr rtprio 2 , 173.Xr setpriority 2 , 174.Xr nice 3 , 175.Xr renice 8 176.Sh HISTORY 177The 178.Nm 179utility appeared in 180.Fx 2.0 , 181but is similar to the HP-UX version. 182.Sh AUTHORS 183.An -nosplit 184.An Henrik Vestergaard Draboel Aq Mt hvd@terry.ping.dk 185is the original author. 186This implementation was substantially rewritten by 187.An David Greenman . 188.Sh CAVEATS 189You can lock yourself out of the system by placing a cpu-heavy 190process in a realtime priority. 191.Sh BUGS 192There is no way to set/view the realtime priority of process 0 193(swapper) (see 194.Xr ps 1 ) . 195.Pp 196There is in 197.Dx 198no way to ensure that a process page is present in memory therefore 199the process may be stopped for pagein (see 200.Xr mprotect 2 , 201.Xr madvise 2 ) . 202.Pp 203Under 204.Dx 205system calls are currently never preempted, therefore non-realtime 206processes can starve realtime processes, or idletime processes can 207starve normal priority processes. 208