2 .\" Copyright (c) 1994, Henrik Vestergaard Draboel
3 .\" All rights reserved.
5 .\" Redistribution and use in source and binary forms, with or without
6 .\" modification, are permitted provided that the following conditions
8 .\" 1. Redistributions of source code must retain the above copyright
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10 .\" 2. Redistributions in binary form must reproduce the above copyright
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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
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39 .Nd execute, examine or modify a utility's or process's realtime
40 or idletime scheduling priority
61 is used for controlling realtime process scheduling.
64 is used for controlling idletime process scheduling, and can be called
65 with the same options as
68 A process with a realtime priority is not subject to priority
69 degradation, and will only be preempted by another process of equal or
70 higher realtime priority.
72 A process with an idle priority will run only when no other
73 process is runnable and then only if its idle priority is equal or
74 greater than all other runnable idle priority processes.
79 when called without arguments will return the realtime priority
80 of the current process.
84 is called with 1 argument, it will return the realtime priority
85 of the process with the specified
90 is specified, the process or program is run at that realtime priority.
93 is specified, the process or program is run as a normal (non-realtime)
98 is specified, the process with the process identifier
100 will be modified, else if
102 is specified, that program is run with its arguments.
105 is an integer between 0 and RTP_PRIO_MAX (usually 31). 0 is the
109 of 0 means "the current process".
111 Only root is allowed to set realtime or idle priority for a process.
115 execute a command, the exit value is that of the command executed.
118 exits 0 on success, and 1 for all other errors.
120 To see which realtime priority the current process is at:
121 .Bd -literal -offset indent -compact
125 To see which realtime priority of process
127 .Bd -literal -offset indent -compact
133 at the lowest realtime priority:
134 .Bd -literal -offset indent -compact
138 To change the realtime priority of process
142 .Bd -literal -offset indent -compact
143 .Sy "rtprio 16 -1423"
148 without realtime priority:
149 .Bd -literal -offset indent -compact
150 .Sy "rtprio -t tcpdump"
153 To change the realtime priority of process
157 (non-realtime/normal priority):
158 .Bd -literal -offset indent -compact
159 .Sy "rtprio -t -1423"
162 To make depend while not disturbing other machine usage:
163 .Bd -literal -offset indent -compact
164 .Sy "idprio 31 make depend"
178 but is similar to the HP-UX version.
180 You can lock yourself out of the system by placing a cpu-heavy
181 process in a realtime priority.
183 There is no way to set/view the realtime priority of process 0
189 no way to ensure that a process page is present in memory therefore
190 the process may be stopped for pagein (see
196 system calls are currently never preempted, therefore non-realtime
197 processes can starve realtime processes, or idletime processes can
198 starve normal priority processes.
200 .An Henrik Vestergaard Draboel Aq hvd@terry.ping.dk
201 is the original author.
205 was substantially rewritten by