Below is a service for slackware which should be located in the 
/etc/rc.d/rc.zram file. It manages zram, which allows for RAM compression.

I recommend setting ZRAM_SIZE to the entire amount of RAM you have.

Don't forget to add to rc.local:
if [ -x /etc/rc.d/rc.zram ]; then
  echo "Activating zram device:  /etc/rc.d/rc.zram start"
  /etc/rc.d/rc.zram start
fi

-------------------------------------------------------------------------------

#!/bin/sh

set -e

ZRAM_DEV="${ZRAM_DEV:-zram0}"
ZRAM_ALGO="${ZRAM_ALGO:-lz4}"
ZRAM_SIZE="${ZRAM_SIZE:-8G}"

zram_start() {
  if ! lsmod | grep -wq '^zram'; then
    modprobe zram
  fi
  if ! grep -wq "^/dev/$ZDEV" /proc/swaps; then
    zramctl "/dev/$ZRAM_DEV" --algorithm "$ZRAM_ALGO" --size "$ZRAM_SIZE" 
    mkswap "/dev/$ZRAM_DEV"
    swapon --discard "/dev/$ZRAM_DEV"
  fi
}

zram_stop() {
  if lsmod | grep -wq '^zram'; then
    if grep -wq "^/dev/$ZRAM_DEV" /proc/swaps; then
      swapoff "/dev/$ZRAM_DEV"
      modprobe -r zram
    fi
  fi
}

zram_status() {
  if ! lsmod | grep -wq '^zram'; then
    echo "zram module not loaded"
    exit 0
  fi

  for ZDEV in $(ls -1 /dev | grep -Ew '^zram[0-9]+'); do
    if ! grep -wq "^/dev/$ZDEV" /proc/swaps; then
      echo "/dev/$ZDEV inactive"
    fi
  done

  zramctl
}

case "$1" in
'start')
  zram_start
  ;;
'stop')
  zram_stop
  ;;
'restart')
  zram_stop
  zram_start
  ;;
'status')
  zram_status
  ;;
*)
  echo "usage $0 start|stop|restart|status"
esac