NAME

       cpulimit -- limits the CPU usage of a process

SYNOPSIS

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

DESCRIPTION

       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

       OPTIONS

       -b, --background
              run cpulimit in the background, freeing up the terminal

       -f, --foreground
              run cpulimit in foreground while waiting for launched process to finish

       -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

       -m, --monitor-forks
              watch and throttle child processes of the target process Warning: It is  usually  a
              bad idea to use this flag, especially on a shell script. The commands in the script
              will each spawn a process which will, in turn, spawn more copies of this program to
              throttle them, bogging down the system. Also, it is possible for a child process to
              die and for its PID to be assigned to another program. When this happens quickly it
              can cause cpulimit to target the new, unintended process before the old information
              has had a chance to be flushed out. Only use the monitor-forks option  in  specific
              cases, ideally on machines without a lot of new processes being spawned.

       -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

EXAMPLES

       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

       # 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)

       # cpulimit -p 1234 -l 50
              limits the CPU usage of the process by acting on its PID, as shown by ps(1)

       # cpulimit -P /usr/bin/foo -l 50
              same as -e but uses the absolute path name

       # /usr/bin/someapp

       # cpulimit -p $! -l 25 -b
              Useful for scripts where you want to throttle the last command run.

       # cpulimit -l 20 firefox
              Launch Firefox web browser and limit its CPU usage to 20%

       # cpulimit -l 25 -- firefox -private
              Launch Firefox web browser in private mode and limit its CPU usage to 25%

       # 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.

       # cpulimit -l 20 -k firefox
              Launch the Firefox program and kill it if the process goes over 20% CPU usage.

       # 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.

NOTES

       •   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 <http://bugs.debian.org/558763>.)

       •   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.

       •   The current version of cpulimit assumes the kernel HZ value 100.

AUTHOR

       This manpage was written for the Debian project by gregor herrmann <gregoa@debian.org> but
       may be used by others.