#!/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

# percent of RAM assigned to zRam swap devices
RATIO=33
# priority of zRam swap devices
PRIORITY=1024

# load system specific configurations
[ -r /etc/default/zram ] && . /etc/default/zram
[ -r /etc/sysconfig/zram ] && . /etc/sysconfig/zram
 
start() {
    # get number of CPUs
    num_cpus=$(grep -c ^processor /proc/cpuinfo 2>/dev/null)
    # if something goes wrong, assume we have 1
    [ $? -eq 0 ] && [ "${num_cpus:-0}" != 0 ] || num_cpus=1
 
    # load kernel module
    if /sbin/modinfo zram 2>/dev/null | grep -q ' zram_num_devices:' 2>/dev/null; then
        /sbin/modprobe zram zram_num_devices=$num_cpus
    elif /sbin/modinfo zram 2>/dev/null | grep -q ' num_devices:' 2>/dev/null; then
        /sbin/modprobe zram num_devices=$num_cpus
    else
        /bin/echo "Unable to load zram kernel module." && exit 1
    fi
 
    # get amount of memory
    mem_total_kb=$(awk '$1 == "MemTotal:" {print $2}' /proc/meminfo)
	
    # assign RATIO% of system memory to zram
    mem_total_zram=$((mem_total_kb * ${RATIO:-33} / 100 * 1024))

    # create one zram swap device per cpu
    for i in $(seq 0 $((num_cpus - 1))); do
        # enable lz4 if supported
        /bin/grep -q lz4 /sys/block/zram$i/comp_algorithm 2>/dev/null && /bin/echo lz4 > /sys/block/zram$i/comp_algorithm 2>/dev/null
        # initialize the device
        /bin/echo $((mem_total_zram / num_cpus)) > /sys/block/zram$i/disksize 2>/dev/null
        # create a swap filesystem
        /sbin/mkswap /dev/zram$i >/dev/null 2>&1
        # activate zram swap device
        /bin/echo -n "Adding swap device /dev/zram$i... "
        /sbin/swapon -p ${PRIORITY:-1024} /dev/zram$i >/dev/null 2>&1
        result=$? && [ ${result} -eq 0 ] && /bin/echo "OK" || /bin/echo "ERROR"
    done
    [ ${result:-0} -ge ${return:-0} ] && return=${result}
}
 
stop() {
    # remove swap devices
    for dev in $(awk '$1 ~ /^\/dev\/zram/ {print $1}' /proc/swaps); do
        /bin/echo -n "Removing swap device $dev... "
        /sbin/swapoff $dev >/dev/null 2>&1
        result=$? && [ ${result} -eq 0 ] && /bin/echo "OK" || /bin/echo "ERROR"
    done
    [ ${result:-0} -ge ${return:-0} ] && return=${result}
    # remove zram kernel module
    if grep -q "^zram " /proc/modules; then
        sleep 1
        /sbin/rmmod zram
    fi
}
 
status() {
    for block in /sys/block/zram*; do
        [ -d "$block" ] && /bin/echo -n "/dev/${block/*\/}: " || continue
        [ $(<$block/compr_data_size) -gt 0 ] \
          && compr_ratio=$(awk "BEGIN { printf \"%.2f\", "$(<$block/orig_data_size)/$(<$block/compr_data_size)" }") \
          || compr_ratio=0
        [ -r $block/stat ] && [ -r $block/mm_stat ] \
          && /usr/bin/awk 'NF==11 {printf("read: %8d, write: %8d, wait: %8d", $1, $5, $11)}' $block/stat && /bin/echo -n ", " \
          && /usr/bin/awk 'NF==7 {printf("orig_data_size: %12d, compr_data_size: %12d", $1, $2)}' $block/mm_stat && /bin/echo -n ", " \
          && /bin/echo "compr_ratio: $compr_ratio" \
          || /bin/echo "read: $(<$block/num_reads), write: $(<$block/num_writes), orig_data_size: $(<$block/orig_data_size), compr_data_size: $(<$block/compr_data_size), compr_ratio: $compr_ratio"
    done
}
 
case "$1" in
    start)
        start
        ;;
    stop)
        stop
        ;;
    restart)
        stop
        start
        ;;
    status)
        status
        ;;
    *)
        /bin/echo "Usage: $0 {start|stop|restart|status}"
esac

exit ${return:-1}