OpenWrt – Rev 1

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

START=15

ram_size()
{
        local line

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

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

        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_applicable()
{
        local zram_dev="$1"

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

        which mkswap >/dev/null || {
                logger -s -t zram_applicable -p daemon.err "[ERROR] 'mkswap' not installed"
                return 1
        }

        which swapon >/dev/null || {
                logger -s -t zram_applicable -p daemon.err "[ERROR] 'swapon' not installed"
                return 1
        }

        which swapoff >/dev/null || {
                logger -s -t zram_applicable -p daemon.err "[ERROR] 'swapoff' not installed"
                return 1
        }
}

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 "$zram_comp_algo" ] || [ ! -e /sys/block/$( basename $dev )/comp_algorithm ]; then
                return 0
        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
}

zram_comp_streams()
{
        local dev="$1"
        local logical_cpus=$( grep -ci "^processor" /proc/cpuinfo )
        [ $logical_cpus -gt 1 ] || return 1
        local zram_comp_streams="$( uci -q get system.@system[0].zram_comp_streams )"
        [ -n "$zram_comp_streams" ] && [ "$zram_comp_streams" -le "$logical_cpus" ] || zram_comp_streams=$logical_cpus
        if [ -e /sys/block/$( basename $dev )/max_comp_streams ]; then
                logger -s -t zram_comp_streams -p daemon.debug "Set max compression streams to '$zram_comp_streams' for zram '$dev'"
                echo $zram_comp_streams > /sys/block/$( basename $dev )/max_comp_streams
        fi
}

start()
{
        local zram_size="$( zram_size )"
        local zram_dev

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

        zram_dev="$( zram_getdev )"
        zram_applicable "$zram_dev" || return 1

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

        zram_reset "$zram_dev" "enforcing defaults"
        zram_comp_algo "$zram_dev"
        zram_comp_streams "$zram_dev"
        echo $(( $zram_size * 1024 * 1024 )) >"/sys/block/$( basename "$zram_dev" )/disksize"
        mkswap "$zram_dev"
        swapon "$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 $zram_dev"
                swapoff "$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
}