1:ionice

From Linux Man Pages

      ionice - get/set program io scheduling class and priority
      
      ionice [-c] [-n] [-p] [COMMAND [ARG...]]

Contents 1 DESCRIPTION 2 OPTIONS 3 EXAMPLES 4 NOTES 5 CATEGORY

DESCRIPTION

      This  program  sets  the  io  scheduling  class  and priority for a program. As of this writing, Linux supports 3
      scheduling classes:
 
      Idle.  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.
 
      Best effort.  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 0-7, with
      lower number being higher priority. Programs running at the same best effort priority are served in a round-robin
      fashion.
 
      Real time.  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,  8  priority levels are defined denoting how big a time slice a given process will receive on each
      scheduling window.
 
      If no arguments or just -p is given, ionice will query the current io scheduling class and priority for that pro-
      cess.

OPTIONS

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

EXAMPLES

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

NOTES

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

CATEGORY