#!/bin/sh /etc/rc.common

START=15

extra_command "compact" "Trigger compaction for all zram swap devices"
extra_command "status" "Print out information & statistics about zram swap devices"

ram_getsize()
{
	local line

	while read line; do case "$line" in MemTotal:*) set $line; echo "$2"; break ;; esac; done </proc/meminfo
}

zram_getsize()	# in megabytes
{
	local zram_size="$( uci -q get system.@system[0].zram_size_mb )"
	local ram_size="$( ram_getsize )"

	if [ -z "$zram_size" ]; then
		# e.g. 6mb for 16mb-routers or 61mb for 128mb-routers
		echo $(( ram_size / 2048 ))
	else
		echo "$zram_size"
	fi
}

zram_dev()
{
	local idx="$1"
	echo "/dev/zram${idx:-0}"
}

zram_reset()
{
	local dev="$1"
	local message="$2"
	local proc_entry="/sys/block/$( basename "$dev" )/reset"

	logger -s -t zram_reset -p daemon.debug "$message via $proc_entry"
	echo "1" >"$proc_entry"
}

zram_getdev()
{
	#get unallocated zram dev
	local zdev=$( zram_dev )

	if [ "$(mount | grep $zdev)" ]; then
		local idx=$(cat /sys/class/zram-control/hot_add)
		zdev="$( zram_dev $idx )"
	fi

	echo $zdev
}

zram_comp_algo()
{
	local dev="$1"
	local zram_comp_algo="$( uci -q get system.@system[0].zram_comp_algo )"

	if [ -z "$zram_comp_algo" ]; then
		# default to lzo, which is always available
		zram_comp_algo="lzo"
	fi

	if [ $(grep -c "$zram_comp_algo" /sys/block/$( basename $dev )/comp_algorithm) -ne 0 ]; then
		logger -s -t zram_comp_algo -p daemon.debug "set compression algorithm '$zram_comp_algo' for zram '$dev'"
		echo $zram_comp_algo > "/sys/block/$( basename $dev )/comp_algorithm"
	else
		logger -s -t zram_comp_algo -p daemon.debug "compression algorithm '$zram_comp_algo' is not supported for '$dev'"
	fi
}

#print various stats info about zram swap device
zram_stats()
{
	local zdev="/sys/block/$( basename "$1" )"

	printf "\nGathering stats info for zram device \"$( basename "$1" )\"\n\n"

	printf "ZRAM\n----\n"
	printf "%-25s - %s\n" "Block device" $zdev
	awk '{ printf "%-25s - %d MiB\n", "Device size", $1/1024/1024 }' <$zdev/disksize
	printf "%-25s - %s\n" "Compression algo" "$(cat $zdev/comp_algorithm)"

	awk 'BEGIN { fmt = "%-25s - %.2f %s\n"
		fmt2 = "%-25s - %d\n"
		print "\nDATA\n----" }
		{ printf fmt, "Original data size", $1/1024/1024, "MiB"
		printf fmt, "Compressed data size", $2/1024/1024, "MiB"
		printf fmt, "Compress ratio", $1/$2, ""
		print "\nMEMORY\n------"
		printf fmt, "Memory used, total", $3/1024/1024, "MiB"
		printf fmt, "Allocator overhead", ($3-$2)/1024/1024, "MiB"
		printf fmt, "Allocator efficiency", $2/$3*100, "%"
		printf fmt, "Maximum memory ever used", $5/1024/1024, "MiB"
		printf fmt, "Memory limit", $4/1024/1024, "MiB"
		print "\nPAGES\n-----"
		printf fmt2, "Same pages count", $6
		printf fmt2, "Pages compacted", $7 }' <$zdev/mm_stat

	awk '{ printf "%-25s - %d\n", "Free pages discarded", $4 }' <$zdev/io_stat
}

zram_compact()
{
	# compact zram device (reduce memory allocation overhead)
	local zdev="/sys/block/$( basename "$1" )"

	local old_mem_used=$(awk '{print $3}' <$zdev/mm_stat)
	local old_overhead=$(awk '{print $3-$2}' <$zdev/mm_stat)

	echo 1 > $zdev/compact

	# If not running interactively, than just return
	[ -z "$PS1" ] && return 0

	echo ""
	echo "Compacting zram device $zdev"
	awk -v old_mem="$old_mem_used" -v ovr="$old_overhead" 'BEGIN { fmt = "%-25s - %.1f %s\n" }
		{ printf fmt, "Memory usage reduced by ", (old_mem-$3)/1024/1024, "MiB"
		printf fmt, "Overhead reduced by", (ovr-($3-$2))/ovr*100, "%" }' <$zdev/mm_stat
}

start()
{
	[ -e /proc/swaps ] || {
		logger -s -t zram_start -p daemon.crit "kernel doesn't support swap"
		return 1
	}

	if [ $( grep -cs zram /proc/swaps ) -ne 0 ]; then
		logger -s -t zram_start -p daemon.notice "zram swap is already mounted"
		return 1
	fi

	local zram_dev="$( zram_getdev )"

	[ -e "$zram_dev" ] || {
		logger -s -t zram_start -p daemon.crit "[ERROR] device '$zram_dev' not found"
		return 1
	}

	local zram_size="$( zram_getsize )"
	local zram_priority="$( uci -q get system.@system[0].zram_priority )"

	if [ -z "$zram_priority" ]; then
		zram_priority="100"
	fi

	logger -s -t zram_start -p daemon.debug "activating '$zram_dev' for swapping ($zram_size MiB)"

	zram_reset "$zram_dev" "enforcing defaults"
	zram_comp_algo "$zram_dev"
	echo $(( $zram_size * 1024 * 1024 )) >"/sys/block/$( basename "$zram_dev" )/disksize"
	busybox mkswap "$zram_dev"
	busybox swapon -d -p $zram_priority "$zram_dev"
}

stop()
{
	local zram_dev

	for zram_dev in $( grep zram /proc/swaps |awk '{print $1}' ); do {
		logger -s -t zram_stop -p daemon.debug "deactivate swap $zram_dev"
		busybox swapoff "$zram_dev" && zram_reset "$zram_dev" "claiming memory back"
		local dev_index="$( echo $zram_dev | grep -o "[0-9]*$" )"
		if [ $dev_index -ne 0 ]; then
			logger -s -t zram_stop -p daemon.debug "removing zram $zram_dev"
			echo $dev_index > /sys/class/zram-control/hot_remove
		fi
	} done
}

# show memory stats for all zram swaps
status()
{
	for zram_dev in $( grep zram /proc/swaps |awk '{print $1}' ); do {
		zram_stats "$zram_dev"
	} done
}

# trigger compaction for all zram swaps
compact()
{
	for zram_dev in $( grep zram /proc/swaps |awk '{print $1}' ); do {
		zram_compact "$zram_dev"
	} done
}
