HOWTO: Set maximum CPU consumption in percentage by any process

[onemyndseye]

Thanks for this. It was most helpful for my home media server ...

I had to make some changes for my needs though as your method for polling for limited PIDs was always returning null... I ended up rewriting abit but the key change was the line:

 LIMITED_PIDS=$(ps -eo args | gawk '$1=="cpulimit" {print $3}')
## changed to (more explaination below) ##
 LIMITED_PIDS=$(ps -eo args | grep cpulimited-bin |grep -v grep |awk '{print $3}')

I needed a version with start/stop built in and also wanted logging.. So my finial code which is still being tested is:

cpulimited.sh

#!/bin/bash
# ==============================================================
# CPU limit daemon - set PID's max. percentage CPU consumptions
# ==============================================================
# Variables
CPU_LIMIT=25                   # Maximum percentage CPU consumption by each PID
DAEMON_INTERVAL=3              # Daemon check interval in seconds
LOG=/var/log/cuplimited.log
CPULIMITED_TMPDIR=/tmp/cpulimited
CONFIG=/etc/cpulimited/cpulimited.conf

BLACKLIST=0
WHITELIST=0
PROCESSES_LIST=

do_help() {
cat <<EOF
Usage:  $0 <options> start|stop
                     -f   ::  Run in foreground
       -c <config file>   ::  Use specified config file

EOF
exit 0
}
do_cpuwatcher() {

# Search and limit violating PIDs
while [ -z "$EXIT" ]; do
   sleep $DAEMON_INTERVAL
   # Check for exit
   DCMD=$(cat "$CONTROL_FILE" |tail -n 1)
   if [ "$DCMD" = "exit" ]; then
     echo "Shutdown requested..."
     PIDS="$(ps ax |grep cpulimited-bin |awk '{print $1}')"
     echo "Removing CPU limits ..."
     kill -9 $PIDS >/dev/null 2>&1
     sleep 1
     cd /tmp
     echo "Cleaning up ..."
     rm -rfd $CPULIMITED_TMPDIR
     echo "Goodbye"
     EXIT=1
     exit 0
   fi
   NEW_PIDS=$(eval "$NEW_PIDS_COMMAND")
   LIMITED_PIDS=$(ps -eo args | grep cpulimited-bin |grep -v grep |awk '{print $3}')
   QUEUE_PIDS=$(comm -23 <(echo "$NEW_PIDS" | sort -u) <(echo "$LIMITED_PIDS" | sort -u) | grep -v '^$')
   if [ -n "$QUEUE_PIDS" ]; then
     echo "These PIDs are already limited: $LIMITED_PIDS"
     echo "These PIDs are now entering the queue: $QUEUE_PIDS"
   fi
   for i in $QUEUE_PIDS; do
        echo "Setting limits for PID: $i"
        if [ -z "$FOREGROUND" ]; then
           ./cpulimited-bin -p $i -l $CPU_LIMIT -z >>$LOG 2>&1 &
        else
           ./cpulimited-bin -p $i -l $CPU_LIMIT -z &
        fi
   done
done
exit 0
}


# Init
##  Process commandline options
while [ "$1" ]; do
   case "$1" in
     -f)
         FOREGROUND=1
         shift 1
      ;;
     -c)
         CONFIG=$2
         shift 2
      ;;
  start)
         CMD=start
         shift 1
         break
       ;;
   stop)
         CMD=stop
         shift 1
         break
      ;;
      *)
       do_help
       break
   esac
done
if [ -z "$CMD" ]; then
  do_help
  exit 0
fi


[ -f $CONFIG ] && . $CONFIG
if [ $BLACKLIST = 1 -a $WHITELIST = 1 ]; then
   echo "Cannot use both whitelist AND blacklist.  Please check your config"
   exit 1
else
   if [ "$BLACKLIST" = "yes" ]; then
     MODE=blacklist
     NEW_PIDS_COMMAND="top -b -n1 -c | grep -E '$BLACK_PROCESSES_LIST' | gawk '\$9>CPU_LIMIT {print \$1}' CPU_LIMIT=$CPU_LIMIT"
   fi
   if [ "$WHITELIST" = "yes" ]; then
     MODE=whitelist
     NEW_PIDS_COMMAND="top -b -n1 -c | gawk 'NR>6' | grep -E -v '$WHITE_PROCESSES_LIST' | gawk '\$9>CPU_LIMIT {print \$1}' CPU_LIMIT=$CPU_LIMIT"
   fi
   if [ -z "$MODE" ]; then
     MODE=supervisor
     NEW_PIDS_COMMAND="top -b -n1 -c | gawk 'NR>6 && \$9>CPU_LIMIT {print \$1}' CPU_LIMIT=$CPU_LIMIT"
   fi
fi

##########  END Init ############


case "$CMD" in
   start)
       echo "Starting up in $MODE mode ..."
       if [ -d $CPULIMITED_TMPDIR ]; then
         echo "Already running or stale tmp directory detected. Aborting ..."
         exit 23
       else
         mkdir -p $CPULIMITED_TMPDIR
         CONTROL_FILE="${CPULIMITED_TMPDIR}/control"
         chown -R root:root $CPULIMITED_TMPDIR
         chmod 700 $CPULIMITED_TMPDIR
         cd $CPULIMITED_TMPDIR
         CPULIMIT=$(which cpulimit)
         ln -s $CPULIMIT cpulimited-bin
         touch $CONTROL_FILE
         if [ -n "$FOREGROUND" ]; then
           # Do not fork
           do_cpuwatcher
         else
           # Fork into the background
           do_cpuwatcher >>$LOG &
         fi
       fi
       ;;
    stop)
        echo "Sending stop signal ..."
        CONTROL_FILE="${CPULIMITED_TMPDIR}/control"
        echo "exit" >$CONTROL_FILE
      ;;
esac

I set a temp directory up for the script and symlinked /usr/bin/cpulimit to ./cpulimited-bin to ease in grep'ing for cpulimit processes spawned by this script. I also added the ability to set changes from a config file. The other change is that BLACKLIST/WHITELIST is a mode toggle (0/1) and PROCESS_LIST would contain the strings to act on... Most all other changes were simply stylistic.

Thanks again!