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Man Pages

Manual Reference Pages  -  CPULIMIT (1)


cpulimit -- limits the CPU usage of a process




cpulimit [TARGET] [OPTIONS...] [ -- PROGRAM]


TARGET must be exactly one of these:
-p, --pid=N
  pid of the process
-e, --exe=FILE
  name of the executable program file
-P, --path=PATH
  absolute path name of the executable program file
-b, --background
  run cpulimit in the background, freeing up the terminal
-c, --cpu specify the number of CPU cores available. Usually this is detected for us.
-l, --limit=N
  percentage of CPU allowed from 1 up. Usually 1 - 100, but can be higher on multi-core CPUs. (mandatory)
-q, --quiet
  Runs in quiet mode, avoids writing update messages to console.
-k, --kill kill target process instead of throttling its CPU usage
-r, --restore
  restore a process killed using the -k flag.
-s, --signal
  send an alternative signal to the watched process when we exit. Default is SIGCONT.
-v, --verbose
  show control statistics
-z, --lazy exit if there is no suitable target process, or if it dies
-- This is the final CPUlimit option. All following options are for another program we will launch.
-h, --help display this help and exit


Assuming you have started ‘foo --bar‘ and you find out with top(1) or ps(1) that this process uses all your CPU time you can either
[sh] cpulimit -e foo -l 50
  limits the CPU usage of the process by acting on the executable program file (note: the argument "--bar" is omitted)
[sh] cpulimit -p 1234 -l 50
  limits the CPU usage of the process by acting on its PID, as shown by ps(1)
[sh] cpulimit -P /usr/bin/foo -l 50
  same as -e but uses the absolute path name
[sh] /usr/bin/someapp
cpulimit -p $! -l 25 -b
  Useful for scripts where you want to throttle the last command run.
[sh] cpulimit -l 20 firefox
  Launch Firefox web browser and limit its CPU usage to 20%
[sh] cpulimit -l 25 -- firefox -private
  Launch Firefox web browser in private mode and limit its CPU usage to 25%
[sh] cpulimit -c 2 -p 12345 -l 25
  The -c flag sets the number of CPU cores the program thinks are available. Usually this is detected for us, but can be over-ridden.
[sh] cpulimit -l 20 -k firefox
  Launch the Firefox program and kill it if the process goes over 20% CPU usage.
[sh] cpulimit -l 20 -p 1234 -s SIGTERM
  Throttle process 1234 at 20% CPU usage. If cpulimit is forced to exit, it sends the watched process the SIGTERM signal.


o cpulimit always sends the SIGSTOP and SIGCONT signals to a process, both to verify that it can control it and to limit the average amount of CPU it consumes. This can result in misleading (annoying) job control messages that indicate that the job has been stopped (when actually it was, but immediately restarted). This can also cause issues with interactive shells that detect or otherwise depend on SIGSTOP/SIGCONT. For example, you may place a job in the foreground, only to see it immediately stopped and restarted in the background. (See also <>.)
o When invoked with the -e or -P options, cpulimit looks for any process under /proc with a name that matches the process name argument given. Furthermore, it uses the first instance of the process found. To control a specific instance of a process, use the -p option and provide a PID.
o The current version of cpulimit assumes the kernel HZ value 100.


This manpage was written for the Debian project by gregor herrmann <> but may be used by others.
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cpulimit CPULIMIT (1) June 2012

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