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
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15 .\" This product includes software developed by Henrik Vestergaard Draboel.
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37 .Nd execute, examine or modify a utility's or process's realtime
38 or idletime scheduling priority
60 utility is used for controlling realtime process scheduling.
64 utility 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.
80 when called without arguments will return the realtime priority
81 of the current process.
85 is called with 1 argument, it will return the realtime priority
86 of the process with the specified
91 is specified, the process or program is run at that realtime priority.
94 is specified, the process or program is run as a normal (non-realtime)
99 is specified, the process with the process identifier
101 will be modified, else if
103 is specified, that program is run with its arguments.
106 is an integer between 0 and RTP_PRIO_MAX (usually 31).
111 of 0 means "the current process".
113 Only root is allowed to set realtime or idle priority for a process.
114 Exceptional privileges can be granted through the
116 policy and the realtime and idletime user groups.
120 .Va security.bsd.unprivileged_idprio
122 If set to non-zero, it lets any user modify the idle priority of processes
125 Note that idle priority increases the chance that a deadlock can occur
126 if a process locks a required resource and then does
131 execute a command, the exit value is that of the command executed.
134 exits 0 on success, and 1 for all other errors.
136 To see which realtime priority the current process is at:
139 To see which realtime priority of process 1423:
144 at the lowest realtime priority:
147 To change the realtime priority of process 1423 to 16:
148 .Dl "rtprio 16 -1423"
152 without realtime priority:
153 .Dl "rtprio -t tcpdump"
155 To change the realtime priority of process 1423
158 (non-realtime/normal priority):
159 .Dl "rtprio -t -1423"
161 To make depend while not disturbing other machine usage:
162 .Dl "idprio 31 make depend"
176 but is similar to the HP-UX version.
179 .An Henrik Vestergaard Draboel Aq Mt hvd@terry.ping.dk
180 is the original author.
184 was substantially rewritten by
187 You can lock yourself out of the system by placing a cpu-heavy
188 process in a realtime priority.
190 There is no way to set/view the realtime priority of process 0
196 no way to ensure that a process page is present in memory therefore
197 the process may be stopped for pagein (see
203 system calls are currently never preempted, therefore non-realtime
204 processes can starve realtime processes, or idletime processes can
205 starve normal priority processes.