2006-12-06 17:26:54 -06:00
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.\" chrt(1) manpage
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.\"
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.\" Copyright (C) 2004 Robert Love
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.\"
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, write to the Free
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.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
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.\" USA.
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.\"
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.\" 2002-05-11 Robert Love <rml@tech9.net>
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.\" Initial version
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.\"
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.TH CHRT "1" "Apr 2003" "schedutils" "Linux User's Manual"
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.SH NAME
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chrt \- manipulate real-time attributes of a process
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.SH SYNOPSIS
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.B chrt
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.RI [ options ]\ prio
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.IR command\ [ arg ]...
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.br
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.B chrt
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.RI [ options ]
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.B \-p
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.RI [ prio ]\ pid
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.SH DESCRIPTION
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.PP
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.BR chrt (1)
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sets or retrieves the real-time scheduling attributes of an existing PID or
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runs COMMAND with the given attributes. Both policy (one of
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.BR SCHED_OTHER ,
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.BR SCHED_FIFO ,
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.BR SCHED_RR ,
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.BR SCHED_BATCH ,
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or
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.BR SCHED_IDLE )
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and priority can be set and retrieved.
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.PP
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The
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.BR SCHED_BATCH
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policy is supported since Linux 2.6.16. The
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.BR SCHED_IDLE
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policy is supported since Linux 2.6.23.
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.SH OPTIONS
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.TP
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.B -p, --pid
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operate on an existing PID and do not launch a new task
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.TP
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.B -b, --batch
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set scheduling policy to
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.BR SCHED_BATCH
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.TP
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.B -f, --fifo
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set scheduling policy to
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.BR SCHED_FIFO
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.TP
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.B -i, --idle
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set schedulng policy to
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.BR SCHED_IDLE
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.TP
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.B -m, --max
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show minimum and maximum valid priorities, then exit
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.TP
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.B -o, --other
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set policy scheduling policy to
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.BR SCHED_OTHER
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.TP
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.B -r, --rr
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set scheduling policy to
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.BR SCHED_RR
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(the default)
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.TP
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.B -h, --help
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display usage information and exit
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.TP
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.B -v, --version
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output version information and exit
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.SH USAGE
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.TP
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The default behavior is to run a new command::
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chrt prio command [arguments]
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.TP
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You can also retrieve the real-time attributes of an existing task:
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chrt -p pid
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.TP
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Or set them:
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chrt -p prio pid
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.SH PERMISSIONS
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A user must possess
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.BR CAP_SYS_NICE
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to change the scheduling attributes of a process. Any user can retrieve the
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scheduling information.
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.SH NOTES
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Only
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.BR SCHED_FIFO ,
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.BR SCHED_OTHER
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and
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.BR SCHED_RR
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are part of POSIX 1003.1b Process Scheduling. The other scheduling attributes
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may be ignored on some systems.
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.SH AUTHOR
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Written by Robert M. Love.
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.SH COPYRIGHT
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Copyright \(co 2004 Robert M. Love
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.br
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This is free software; see the source for copying conditions. There is NO
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warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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.SH "SEE ALSO"
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.BR taskset (1),
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.BR nice (1),
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.BR renice (1)
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.sp
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See
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.BR sched_setscheduler (2)
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for a description of the Linux scheduling scheme.
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.SH AVAILABILITY
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The chrt command is part of the util-linux-ng package and is available from
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ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
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