-.TH ionice "1" "August 2005" ionice
+.TH IONICE 1 "July 2011" "util-linux" "User Commands"
.SH NAME
-ionice \- get/set program io scheduling class and priority
+ionice \- set or get process I/O scheduling class and priority
.SH SYNOPSIS
.B ionice
-[\fI-c\fR] \fI[-n\fR] [\fI-p\fR] [COMMAND [ARG...]]
-
+.RB [ \-c
+.IR class ]
+.RB [ \-n
+.IR level ]
+.RB [ \-t ]
+.B \-p
+.IR PID ...
+.br
+.B ionice
+.RB [ \-c
+.IR class ]
+.RB [ \-n
+.IR level ]
+.RB [ \-t ]
+.B \-P
+.IR PGID ...
+.br
+.B ionice
+.RB [ \-c
+.IR class ]
+.RB [ \-n
+.IR level ]
+.RB [ \-t ]
+.B \-u
+.IR UID ...
+.br
+.B ionice
+.RB [ \-c
+.IR class ]
+.RB [ \-n
+.IR level ]
+.RB [ \-t ]
+.IR "command " [ argument ...]
.SH DESCRIPTION
-This program sets the io scheduling class and priority for a program. As of
-this writing, Linux supports 3 scheduling classes:
+This program sets or gets the I/O scheduling class and priority for a program.
+If no arguments or just \fB\-p\fR is given, \fBionice\fR will query the current
+I/O scheduling class and priority for that process.
+
+When \fIcommand\fR is given,
+.B ionice
+will run this command with the given arguments.
+If no \fIclass\fR is specified, then
+.I command
+will be executed with the "best-effort" scheduling class. The default
+priority level is 4.
-\fBIdle\fR.
-A program running with idle io priority will only get disk time when no other
-program has asked for disk io for a defined grace period. The impact of idle
-io processes on normal system activity should be zero. This scheduling
-class does not take a priority argument. Presently, this scheduling class
+As of this writing, a process can be in one of three scheduling classes:
+.IP "\fBIdle\fP"
+A program running with idle I/O priority will only get disk time when no other
+program has asked for disk I/O for a defined grace period. The impact of an
+idle I/O process on normal system activity should be zero. This scheduling
+class does not take a priority argument. Presently, this scheduling class
is permitted for an ordinary user (since kernel 2.6.25).
+.IP "\fBBest-effort\fP"
+This is the effective scheduling class for any process that has not asked for
+a specific I/O priority.
+This class takes a priority argument from \fI0-7\fR, with a lower
+number being higher priority. Programs running at the same best-effort
+priority are served in a round-robin fashion.
+Note that before kernel 2.6.26 a process that has not asked for an I/O priority
+formally uses "\fBnone\fP" as scheduling class, but the I/O scheduler will treat
+such processes as if it were in the best-effort class. The priority within the
+best-effort class will be dynamically derived from the CPU nice level of the
+process: io_priority = (cpu_nice + 20) / 5.
-\fBBest effort\fR.
-This is the default scheduling class for any process that hasn't asked for
-a specific io priority. Programs inherit the CPU nice setting for io
-priorities. This class takes a priority argument from \fI0-7\fR, with lower
-number being higher priority. Programs running at the same best effort
-priority are served in a round-robin fashion.
+For kernels after 2.6.26 with the CFQ I/O scheduler, a process that has not asked
+for an I/O priority inherits its CPU scheduling class. The I/O priority is derived
+from the CPU nice level of the process (same as before kernel 2.6.26).
-\fBReal time\fR.
+.IP "\fBRealtime\fP"
The RT scheduling class is given first access to the disk, regardless of
-what else is going on in the system. Thus the RT class needs to be used with
-some care, as it can starve other processes. As with the best effort class,
+what else is going on in the system. Thus the RT class needs to be used with
+some care, as it can starve other processes. As with the best-effort class,
8 priority levels are defined denoting how big a time slice a given process
-will receive on each scheduling window. This scheduling class is not
+will receive on each scheduling window. This scheduling class is not
permitted for an ordinary (i.e., non-root) user.
-
-If no arguments or just \fI-p\fR is given, \fIionice\fR will query the
-current io scheduling class and priority for that process.
-
.SH OPTIONS
+.TP
+.BR \-c , " \-\-class " \fIclass\fR
+Specify the name or number of the scheduling class to use; \fI0\fR for none,
+\fI1\fR for realtime, \fI2\fR for best-effort, \fI3\fR for idle.
+.TP
+.BR \-n , " \-\-classdata " \fIlevel\fR
+Specify the scheduling class data. This only has an effect if the class
+accepts an argument. For realtime and best-effort, \fI0-7\fR are valid data
+(priority levels), and \fI0\fR represents the highest priority level.
+.TP
+.BR \-p , " \-\-pid " \fIPID\fR...
+Specify the process IDs of running processes for which to get or set the
+scheduling parameters.
+.TP
+.BR \-P , " \-\-pgid " \fIPGID\fR...
+Specify the process group IDs of running processes for which to get or set the
+scheduling parameters.
+.TP
+.BR \-t , " \-\-ignore"
+Ignore failure to set the requested priority. If \fIcommand\fR was specified,
+run it even in case it was not possible to set the desired scheduling priority,
+which can happen due to insufficient privileges or an old kernel version.
+.TP
+.BR \-h , " \-\-help"
+Display help text and exit.
+.TP
+.BR \-u , " \-\-uid " \fIUID\fR...
+Specify the user IDs of running processes for which to get or set the
+scheduling parameters.
+.TP
+.BR \-V , " \-\-version"
+Display version information and exit.
+.SH NOTES
+Linux supports I/O scheduling priorities and classes since 2.6.13 with the CFQ
+I/O scheduler.
+.SH EXAMPLE
.LP
.TP 7
-\fB-c\fP
-The scheduling class. 1 for real time, 2 for best-effort, 3 for idle.
-.TP 7
-\fB-n\fP
-The scheduling class data. This defines the class data, if the class
-accepts an argument. For real time and best-effort, \fI0-7\fR is valid
-data.
-.TP 7
-\fB-p\fP
-Pass in a process pid to change an already running process. If this argument
-is not given, \fBionice\fP will run the listed program with the given
-parameters.
-.TP 7
-\fB-t\fP
-Ignore failure to set requested priority. If COMMAND is specified, run it
-even in case it was not possible to set desired scheduling priority, what
-can happen due to insufficient privilegies or old kernel version.
-
-.SH EXAMPLES
-.LP
-.TP 7
-# \fBionice\fP -c3 -p89
+# \fBionice\fP \-c 3 \-p 89
.TP 7
-Sets process with PID 89 as an idle io process.
+Sets process with PID 89 as an idle I/O process.
.TP 7
-# \fBionice\fP -c2 -n0 bash
+# \fBionice\fP \-c 2 \-n 0 bash
.TP 7
Runs 'bash' as a best-effort program with highest priority.
.TP 7
-# \fBionice\fP -p89
+# \fBionice\fP \-p 89 91
.TP 7
-Returns the class and priority of the process with PID 89.
-
-.SH NOTES
-Linux supports io scheduling priorities and classes since 2.6.13 with the CFQ
-io scheduler.
-
+Prints the class and priority of the processes with PID 89 and 91.
.SH AUTHORS
-Jens Axboe <axboe@suse.de>
-
+.nf
+Jens Axboe <jens@axboe.dk>
+Karel Zak <kzak@redhat.com>
+.fi
+.SH SEE ALSO
+.BR ioprio_set (2)
.SH AVAILABILITY
-The ionice command is part of the util-linux-ng package and is available from
-ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
+The ionice command is part of the util-linux package and is available from
+https://www.kernel.org/pub/linux/utils/util-linux/.
projects / thirdparty / util-linux.git / blobdiff