189 lines
5.3 KiB
Groff
189 lines
5.3 KiB
Groff
.\" $NetBSD: renice.8,v 1.18 2020/10/23 16:14:40 wiz Exp $
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.\"
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.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. 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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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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.\" from: @(#)renice.8 8.1 (Berkeley) 6/9/93
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.\"
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.Dd October 22, 2020
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.Dt RENICE 8
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.Os
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.Sh NAME
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.Nm renice
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.Nd alter priority of running processes
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.Sh SYNOPSIS
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.Nm
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.Ar priority
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.Oo
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.Op Fl gpu
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.Ar who ...
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.Oc
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.Ar ...
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.Nm
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.Fl n
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.Ar increment
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.Oo
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.Op Fl gpu
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.Ar who ...
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.Oc
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.Ar ...
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.Sh DESCRIPTION
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.Nm
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alters the
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scheduling priority of one or more running processes.
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The first argument is the new priority to apply, or if
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.Fl n
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is given, the change to make (applied additively) to the priority.
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This argument may be negative.
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(The interpretation of priorities is discussed below.)
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.Pp
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The following
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.Ar who
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parameters name the target processes, as either process IDs, process
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group IDs, or user names.
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The
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.Fl gpu
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options control the interpretation as follows:
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.Bl -tag -width Ds
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.It Fl g
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Interpret
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.Ar who
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parameters as process group ID's.
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.It Fl p
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Interpret
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.Ar who
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parameters as process IDs.
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This is the default.
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.It Fl u
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Interpret
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.Ar who
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parameters as user names.
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.El
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.Pp
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Each
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.Ar who
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parameter is processed separately and updates the priority of the
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processes it names as follows:
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.Bl -tag -width "with Ds"
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.It with Fl g
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All processes in the process group are updated to the selected
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priority.
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If an
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.Ar increment
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is used, the increment is added to the highest priority found among
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the members of the process group prior to the change.
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.It with Fl p
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The named process is updated to the selected priority.
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If an
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.Ar increment
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is used, the increment is added to the process's previous priority.
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.It with Fl u
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All processes belonging to the specified user are updated to the
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selected priority.
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If an
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.Ar increment
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is used, the increment is added to the highest priority found among
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the processes belonging to the user prior to the change.
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.El
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.Pp
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In conventional terminology a
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.Dq high priority
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process receives a lot of CPU time and a
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.Dq low priority
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process receives relatively little.
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.Dq Niceness
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is the inverse concept: a process with a high niceness level receives
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relatively little CPU time.
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It is about the process being nice to the rest of the system, rather
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than the system being nice to the process.
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.Pp
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The numerical priority values accepted by
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.Nm
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are
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.Em called
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priorities but are actually nicenesses.
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They range from
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.Dv PRIO_MIN
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(\-20)
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to
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.Dv PRIO_MAX
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(20).
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.Dv PRIO_MIN
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is the highest priority, lowest niceness, and receives the most CPU
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time.
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.Dv PRIO_MAX
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is the lowest priority, highest niceness, and receives the least CPU
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time.
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This is confusing but enshrined in historical practice and standards.
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If in doubt, check with
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.Xr ps 1 :
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processes running with elevated priority (getting more CPU time)
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include
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.Sq <
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in the FLAGS column; processes running with reduced priority
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(getting less CPU time) show
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.Sq N
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for
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.Dq nice
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in FLAGS.
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The default priority is 0.
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.Pp
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At priority 20, processes will specifically run only when nothing else
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wants to.
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.Pp
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Users other than the super-user may only alter the priority of
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processes they own,
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and only by increasing the niceness.
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(This prevents overriding administrative fiats.)
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The super-user
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may alter the priority of any process to any legal value.
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.Sh FILES
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.Bl -tag -width /etc/passwd -compact
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.It Pa /etc/passwd
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to map user names to user ID's
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.El
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.Sh EXAMPLES
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.Bd -literal -offset indent
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renice +1 987 -u daemon root -p 32
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.Ed
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.Pp
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changes the priority of process ID's 987 and 32, and
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all processes owned by users daemon and root.
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.Sh SEE ALSO
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.Xr nice 1 ,
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.Xr prenice 1 ,
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.Xr getpriority 2 ,
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.Xr setpriority 2
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.Sh HISTORY
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The
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.Nm
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command appeared in
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.Bx 4.0 .
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.Sh BUGS
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Non-super-users cannot increase scheduling priorities of their own processes,
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even if they were the ones that decreased the priorities in the first place.
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