159 lines
3.9 KiB
Groff
159 lines
3.9 KiB
Groff
.\" 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,
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.\" version 2, as published by the Free Software Foundation.
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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 License along
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.\" with this program; if not, write to the Free Software Foundation, Inc.,
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.\" 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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.\"
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.TH CHRT 1 "August 2014" "util-linux" "User Commands"
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.SH NAME
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chrt \- manipulate the real-time attributes of a process
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.SH SYNOPSIS
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.B chrt
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[options]
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.IR priority\ command\ [ argument ...]
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.br
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.B chrt
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[options]
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.B \-p
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.RI [ priority ]\ pid
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.SH DESCRIPTION
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.PP
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.B chrt
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sets or retrieves the real-time scheduling attributes of an existing \fIpid\fR,
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or runs \fIcommand\fR with the given attributes. Both the 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 the 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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.PP
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The
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.BR SCHED_RESET_ON_FORK
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flag for policies SCHED_RR and SCHED_FIFO is supported
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since Linux 2.6.31.
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.SH OPTIONS
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.TP
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.BR -a ,\ --all-tasks
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Set or retrieve the scheduling attributes of all the tasks (threads) for a
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given PID.
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.TP
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.BR -b ,\ --batch
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Set scheduling policy to
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.B SCHED_BATCH
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(Linux-specific). The priority argument has to be set to zero.
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.TP
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.BR -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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.BR -i ,\ --idle
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Set scheduling policy to
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.B SCHED_IDLE
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(Linux-specific). The priority argument has to be set to zero.
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.TP
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.BR -m ,\ --max
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Show minimum and maximum valid priorities, then exit.
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.TP
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.BR -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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.BR -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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.BR -R ,\ --reset-on-fork
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Add
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.B SCHED_RESET_ON_FORK
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flag to the
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.B SCHED_FIFO
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or
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.B SCHED_RR
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scheduling policy (Linux-specific).
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.TP
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.BR -r ,\ --rr
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Set scheduling policy to
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.BR SCHED_RR .
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When policy is not defined the
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.B SCHED_RR
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is used as default.
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.TP
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.BR -v ,\ --verbose
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Show status information.
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.TP
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.BR -V ,\ --version
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Display version information and exit.
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.TP
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.BR -h ,\ --help
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Display help text 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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.B chrt
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.I priority
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.IR 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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.B chrt \-p
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.I pid
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.TP
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Or set them:
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.B chrt \-r \-p
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.I priority 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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.P
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Linux default scheduling policy is
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.BR SCHED_OTHER .
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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 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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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 AVAILABILITY
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The chrt command is part of the util-linux package and is available from
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ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
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