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  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.

       -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.