#!/bin/sh
zram_module="/lib/modules/zram.ko"
# number of memory can be used as zram
# 0.25 is used for SSD cache, we assume the remaining memory 0.75 *0.4 = 0.3 is swappable
sys_mem_ratio=0.3

op=$1

round_up()
{
	local value=$1
	printf %0.f $value
}

math()
{
	local formula=$1
	php -r "echo($formula);"
}

byte_mb()
{
	local byte=$1
	local value=`math "$value/1024/1024"`
	round_up $value
}

print_entry()
{
	local entry=$1
	local name=`basename $entry`
	local mb="0"
	if test -e $entry ; then
		value=`cat $entry`
		mb=`byte_mb $value`
		echo "$name: ${mb}MB"
	fi
}

print_value()
{
	local entry=$1
	local name=`basename $entry`
	if test -e $entry ; then
		value=`cat $entry`
		echo "$name: $value"
	fi
}

get_cpu_core()
{
	local cores=`cat /proc/cpuinfo | grep "cpu cores" | head -n 1`

	if test "$cores" = "" ; then
		# For platforms that don't have "cpu cores" entry
		cat /proc/cpuinfo | grep processor | wc -l
	else
		echo "$cores" | sed -e "s:cpu cores\t\:\s*\([0-9]*\):\1:g"
	fi
}

get_mem_total_kb()
{
	cat /proc/meminfo | grep MemTotal | sed -e "s:MemTotal\:\s*\([0-9]*\) kB:\1:g"
}

round_up()
{
	local float=$1
	printf "%0.f" $float
}

zram_print()
{
	local msg=$1
	echo "synozram: $msg"
}

zram_setup()
{
	local size_mb=0
	local mem_total_kb=`get_mem_total_kb`
	local cpu_core=`get_cpu_core`
	local last_index=$(($cpu_core -1))
	local node=""
	local node_base=""

	zram_print "Starting..."

	if test ! -e "$zram_module" ;then
		zram_print "zRAM is not supported"
		return
	fi

	# Install lzo modules if needed
	if test -e "/lib/modules/lzo_compress.ko" ;  then
		insmod /lib/modules/lzo_compress.ko
		if test "$?" != "0" ; then
			zram_print "Can't insmod lzo_compress.ko"
		fi
	fi

	if test -e "/lib/modules/lzo_decompress.ko" ; then
		insmod /lib/modules/lzo_decompress.ko
		if test "$?" != "0" ; then
			zram_print "Can't insmod lzo_decompress.ko"
		fi
	fi

	if cat /proc/swaps | grep zram > /dev/null 2>&1 ; then
		zram_print "WARNING: zRAM has started"
		exit
	fi

	# compressed ratio is about 2
	size_mb=`math "$mem_total_kb/1024*$sys_mem_ratio/$cpu_core*2"`
	size_mb=`round_up $size_mb`

	if  lsmod | grep zram ; then
		rmmod zram
	fi
	insmod $zram_module num_devices=$cpu_core

	for i in `seq 0 $last_index` ;do
		node="/dev/zram$i"
		node_base=`basename $node`
		echo $(($size_mb*1024*1024)) > /sys/block/$node_base/disksize

		if test ! -e "$node" ; then
			mknod $node b 252 $i
		fi

		mkswap $node
		swapon -p 1 $node
	done

	cat /proc/swaps

	zram_print "Started"

}

zram_unset()
{
	local size_mb=0
	local cpu_core=`get_cpu_core`
	local last_index=$(($cpu_core -1))
	local node=""

	zram_print "Stopping..."
	if ! cat /proc/swaps | grep zram > /dev/null 2>&1 ; then
		zram_print "zRam can not be stopped due to it doesn't start"
		exit
	fi

	for i in `seq 0 $last_index` ;do
		node="/dev/zram$i"
		if test -e "$node" ; then
			swapoff $node
			rm $node
		fi
	done

	if lsmod | grep zram ; then
		rmmod zram
	fi

	if lsmod | grep lzo_compress; then
		rmmod lzo_compress
	fi

	if lsmod | grep lzo_decompress; then
		rmmod lzo_decompress
	fi

	cat /proc/swaps

	zram_print "Stopped"
}

zram_watch()
{
	local cpu_core=`get_cpu_core`
	local last_index=$(($cpu_core -1))

	while true; do
		clear
		echo "===========`date`==================="
		cat /proc/meminfo | head -n 5
		echo "------------------------"
		for i in `seq 0 $last_index` ;do
			echo "zram$i:"
			# orig_data_size + zero_pages*4k is the original data size
			print_entry "/sys/block/zram$i/orig_data_size"
			print_value "/sys/block/zram$i/zero_pages"
			print_entry "/sys/block/zram$i/compr_data_size"
			print_entry "/sys/block/zram$i/mem_used_total"
			print_value "/sys/block/zram$i/num_reads"
			print_value "/sys/block/zram$i/num_writes"
			echo "------------------------"
		done
		echo ======================================
		cat /proc/swaps
		sleep 5
	done
}

case "$op" in
	start)
		zram_setup
		;;
	stop)
		zram_unset
		;;
	watch)
		zram_watch
		;;
	*)
		echo "unknown option"
		;;
esac