zram

#!/bin/bash
### BEGIN INIT INFO
# Provides: zram
# Required-Start:
# Required-Stop:
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Increased Performance In Linux With zRam (Virtual Swap Compressed in RAM)
# Description: Adapted from systemd scripts at https://github.com/mystilleef/FedoraZram
### END INIT INFO

kernel_version_at_least() {
    ver=$(uname -r)
    [ "$1" = "$ver" ] && return 1 || [ "$1" = "`echo -e "$1\n$ver" | sort -V | head -n1`" ]
}

start() {
    # get the number of CPUs
    num_cpus=$(grep -c processor /proc/cpuinfo)
    # if something goes wrong, assume we have 1
    [ "$num_cpus" != 0 ] || num_cpus=1

    # set decremented number of CPUs
    decr_num_cpus=$((num_cpus - 1))

    # get the amount of memory in the machine
    mem_total_kb=$(grep MemTotal /proc/meminfo | grep -E --only-matching '[[:digit:]]+')
    mem_total=$((mem_total_kb * 1024))

    # load dependency modules
    if kernel_version_at_least 3.8; then
        modprobe zram num_devices=$num_cpus
    elif kernel_version_at_least 3.2; then
        modprobe zram zram_num_devices=$num_cpus
    else 
        echo "Your kernel is too old!"
        RETVAL=1
    fi

    if ! [[ $RETVAL -eq 1 ]]; then
        # initialize the devices
        for i in $(seq 0 $decr_num_cpus); do
            echo $((mem_total / num_cpus)) > /sys/block/zram$i/disksize
        done

        # Creating swap filesystems
        for i in $(seq 0 $decr_num_cpus); do
            mkswap /dev/zram$i
        done

        # Switch the swaps on
        for i in $(seq 0 $decr_num_cpus); do
            swapon -p 100 /dev/zram$i
        done
    fi
}

stop() {
    # get the number of CPUs
    num_cpus=$(grep -c processor /proc/cpuinfo)

    # set decremented number of CPUs
    decr_num_cpus=$((num_cpus - 1))

    # Switching off swap
    for i in $(seq 0 $decr_num_cpus); do
        if [ "$(grep /dev/zram$i /proc/swaps)" != "" ]; then
            swapoff /dev/zram$i
            sleep 1
        fi
    done

    sleep 1
    rmmod zram
}

case "$1" in
    start)
        start
        ;;
    stop)
        stop
        ;;
    restart)
        stop
        sleep 3
        start
        ;;
    *)
        echo "Usage: $0 {start|stop|restart}"
        RETVAL=1
esac