| .\" chrt(1) manpage |
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| .\" Copyright (C) 2004 Robert Love |
| .\" Copyright (C) 2015 Karel Zak <kzak@redhat.com> |
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| .TH CHRT 1 "January 2016" "util-linux" "User Commands" |
| .SH NAME |
| chrt \- manipulate the real-time attributes of a process |
| .SH SYNOPSIS |
| .B chrt |
| [options] |
| .IR priority\ command\ [ argument ...] |
| .br |
| .B chrt |
| [options] |
| .B \-p |
| .RI [ priority ]\ pid |
| .SH DESCRIPTION |
| .PP |
| .B chrt |
| sets or retrieves the real-time scheduling attributes of an existing \fIpid\fR, |
| or runs \fIcommand\fR with the given attributes. |
| |
| .SH POLICIES |
| .TP |
| \fB\-o\fR, \fB\-\-other\fR |
| Set scheduling policy to |
| .BR SCHED_OTHER . |
| This is the default Linux scheduling policy. |
| .TP |
| \fB\-f\fR, \fB\-\-fifo\fR |
| Set scheduling policy to \fBSCHED_FIFO\fR. |
| .TP |
| \fB\-r\fR, \fB\-\-rr\fR |
| Set scheduling policy to |
| .BR SCHED_RR . |
| When no policy is defined, the |
| .B SCHED_RR |
| is used as the default. |
| .TP |
| \fB\-b\fR, \fB\-\-batch\fR |
| Set scheduling policy to |
| .B SCHED_BATCH |
| (Linux-specific, supported since 2.6.16). The priority argument has to be set to zero. |
| .TP |
| \fB\-i\fR, \fB\-\-idle\fR |
| Set scheduling policy to |
| .B SCHED_IDLE |
| (Linux-specific, supported since 2.6.23). The priority argument has to be set to zero. |
| .TP |
| .BR -d ,\ --deadline |
| Set scheduling policy to |
| .B SCHED_DEADLINE |
| (Linux-specific, supported since 3.14). The priority argument has to be set to zero. |
| See also \fB\-\-sched\-runtime\fR, \fB\-\-sched\-deadline\fR and |
| \fB\-\-sched\-period\fR. The relation between the options required by the kernel is |
| runtime <= deadline <= period. |
| .B chrt |
| copies \fIperiod\fR to \fIdeadline\fR if \fB\-\-sched\-deadline\fR is not specified and |
| \fIdeadline\fR to \fIruntime\fR if \fB\-\-sched\-runtime\fR is not specified. |
| It means that at least \fB\-\-sched\-period\fR has to be specified. See |
| .BR sched (7) |
| for more details. |
| |
| .SH "SCHEDULING OPTIONS" |
| .TP |
| \fB\-T\fR, \fB\-\-sched\-runtime\fR \fInanoseconds\fR |
| Specifies runtime parameter for SCHED_DEADLINE policy (Linux-specific). |
| .TP |
| \fB\-P\fR, \fB\-\-sched\-period\fR \fInanoseconds\fR |
| Specifies period parameter for SCHED_DEADLINE policy (Linux-specific). |
| .TP |
| \fB\-D\fR, \fB\-\-sched\-deadline\fR \fInanoseconds\fR |
| Specifies deadline parameter for SCHED_DEADLINE policy (Linux-specific). |
| .TP |
| \fB\-R\fR, \fB\-\-reset-on-fork\fR |
| Add |
| .B SCHED_RESET_ON_FORK |
| flag to the |
| .B SCHED_FIFO |
| or |
| .B SCHED_RR |
| scheduling policy (Linux-specific, supported since 2.6.31). |
| |
| .SH OPTIONS |
| .TP |
| .BR -a ,\ --all-tasks |
| Set or retrieve the scheduling attributes of all the tasks (threads) for a |
| given PID. |
| .TP |
| .BR -m ,\ --max |
| Show minimum and maximum valid priorities, then exit. |
| .TP |
| .BR -p ,\ --pid |
| Operate on an existing PID and do not launch a new task. |
| .TP |
| .BR -v ,\ --verbose |
| Show status information. |
| .TP |
| .BR -V ,\ --version |
| Display version information and exit. |
| .TP |
| .BR -h ,\ --help |
| Display help text and exit. |
| .SH USAGE |
| .TP |
| The default behavior is to run a new command: |
| .B chrt |
| .I priority |
| .IR command\ [ arguments ] |
| .TP |
| You can also retrieve the real-time attributes of an existing task: |
| .B chrt \-p |
| .I pid |
| .TP |
| Or set them: |
| .B chrt \-r \-p |
| .I priority pid |
| .SH PERMISSIONS |
| A user must possess |
| .B CAP_SYS_NICE |
| to change the scheduling attributes of a process. Any user can retrieve the |
| scheduling information. |
| |
| .SH NOTES |
| Only |
| .BR SCHED_FIFO , |
| .B SCHED_OTHER |
| and |
| .B SCHED_RR |
| are part of POSIX 1003.1b Process Scheduling. The other scheduling attributes |
| may be ignored on some systems. |
| .P |
| Linux' default scheduling policy is |
| .BR SCHED_OTHER . |
| .SH SEE ALSO |
| .BR nice (1), |
| .BR renice (1), |
| .BR taskset (1), |
| .BR sched (7) |
| .sp |
| See |
| .BR sched_setscheduler (2) |
| for a description of the Linux scheduling scheme. |
| .SH AUTHORS |
| .UR rml@tech9.net |
| Robert Love |
| .UE |
| .br |
| .UR kzak@redhat.com |
| Karel Zak |
| .UE |
| .SH AVAILABILITY |
| The chrt command is part of the util-linux package and is available from |
| https://www.kernel.org/pub/linux/utils/util-linux/. |