72 lines
2.3 KiB
Groff
72 lines
2.3 KiB
Groff
.TH ionice "1" "August 2005" ionice
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.SH NAME
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ionice \- get/set program io scheduling class and priority
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.SH SYNOPSIS
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.B ionice
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[\fI-c\fR] \fI[-n\fR] [\fI-p\fR] [COMMAND [ARG...]]
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.SH DESCRIPTION
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This program sets the io scheduling class and priority for a program. As of
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this writing, Linux supports 3 scheduling classes:
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\fBIdle\fR.
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A program running with idle io priority will only get disk time when no other
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program has asked for disk io for a defined grace period. The impact of idle
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io processes on normal system activity should be zero. This scheduling
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class does not take a priority argument.
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\fBBest effort\fR.
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This is the default scheduling class for any process that hasn't asked for
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a specific io priority. Programs inherit the CPU nice setting for io
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priorities. This class takes a priority argument from \fI0-7\fR, with lower
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number being higher priority. Programs running at the same best effort
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priority are served in a round-robin fashion.
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\fBReal time\fR.
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The RT scheduling class is given first access to the disk, regardless of
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what else is going on in the system. Thus the RT class needs to be used with
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some care, as it can starve other processes. As with the best effort class,
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8 priority levels are defined denoting how big a time slice a given process
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will receive on each scheduling window.
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If no arguments or just \fI-p\fR is given, \fIionice\fR will query the
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current io scheduling class and priority for that process.
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.SH OPTIONS
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.LP
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.TP 7
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\fB-c\fP
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The scheduling class. 1 for real time, 2 for best-effort, 3 for idle.
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.TP 7
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\fB-n\fP
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The scheduling class data. This defines the class data, if the class
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accepts an argument. For real time and best-effort, \fI0-7\fR is valid
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data.
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.TP 7
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\fB-p\fP
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Pass in a process pid to change an already running process. If this argument
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is not given, \fBionice\fP will run the listed program with the given
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parameters.
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.SH EXAMPLES
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.LP
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.TP 7
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# \fBionice\fP -c3 -p89
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.TP 7
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Sets process with PID 89 as an idle io process.
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.TP 7
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# \fBionice\fP -c2 -n0 bash
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.TP 7
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Runs 'bash' as a best-effort program with highest priority.
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.TP 7
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# \fBionice\fP -p89
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.TP 7
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Returns the class and priority of the process with PID 89.
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.SH NOTES
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Linux supports io scheduling priorities and classes since 2.6.13 with the CFQ
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io scheduler.
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.SH AUTHORS
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Jens Axboe <axboe@suse.de>
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