1ionice(1)                   General Commands Manual                  ionice(1)
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NAME

6       ionice - get/set program io scheduling class and priority
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SYNOPSIS

9       ionice [-c] [-n] [-p] [COMMAND [ARG...]]
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DESCRIPTION

13       This  program  sets the io scheduling class and priority for a program.
14       As of this writing, Linux supports 3 scheduling classes:
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16       Idle.  A program running with idle io priority will only get disk  time
17       when no other program has asked for disk io for a defined grace period.
18       The impact of idle io processes on normal  system  activity  should  be
19       zero. This scheduling class does not take a priority argument.
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21       Best effort.  This is the default scheduling class for any process that
22       hasn't asked for a specific io priority. Programs inherit the CPU  nice
23       setting  for  io  priorities. This class takes a priority argument from
24       0-7, with lower number being higher priority. Programs running  at  the
25       same best effort priority are served in a round-robin fashion.
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27       Real  time.  The RT scheduling class is given first access to the disk,
28       regardless of what else is going on in the system. Thus  the  RT  class
29       needs  to  be used with some care, as it can starve other processes. As
30       with the best effort class, 8 priority levels are defined denoting  how
31       big  a  time slice a given process will receive on each scheduling win‐
32       dow.
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34       If no arguments or just -p is given, ionice will query the  current  io
35       scheduling class and priority for that process.
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OPTIONS

39       -c     The  scheduling class. 1 for real time, 2 for best-effort, 3 for
40              idle.
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42       -n     The scheduling class data. This defines the class data,  if  the
43              class accepts an argument. For real time and best-effort, 0-7 is
44              valid data.
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46       -p     Pass in a process pid to change an already running  process.  If
47              this  argument  is not given, ionice will run the listed program
48              with the given parameters.
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EXAMPLES

52       # ionice -c3 -p89
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54       Sets process with PID 89 as an idle io process.
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56       # ionice -c2 -n0 bash
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58       Runs 'bash' as a best-effort program with highest priority.
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60       # ionice -p89
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62       Returns the class and priority of the process with PID 89.
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NOTES

66       Linux supports io scheduling priorities and classes since  2.6.13  with
67       the CFQ io scheduler.
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AUTHORS

71       Jens Axboe <axboe@suse.de>
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75ionice                            August 2005                        ionice(1)
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