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

       -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

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.