OpenWrt – Rev 3

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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"

        grep -sq ^"$zram_dev " /proc/swaps && {
                logger -s -t zram_applicable -p daemon.notice "[OK] '$zram_dev' already active"
                return 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 core="$1"

        echo "/dev/zram${core:-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"
}

list_cpu_idx()
{
        # Offset by 1 if /dev/zram0 is in use by /tmp
        if [ "$(mount | grep /dev/zram0)" ]; then
                local line i=1
                # Hot-add new ZRAM device (if necessary)
                if [ ! -b /dev/zram1 ]; then 
                        cat /sys/class/zram-control/hot_add
                fi
        else
                local line i=0
        fi
        
        while read line; do {
                case "$line" in
                        [Pp]rocessor*)
                                echo $i
                                i=$(( $i + 1 ))
                        ;;
                esac
        } done <"/proc/cpuinfo"
}

start()
{
        # http://shmilyxbq-compcache.googlecode.com/hg/README
        # if >1 cpu_core, reinit kmodule with e.g. num_devices=4

        local zram_size="$( zram_size )"
        local zram_dev core

        for core in $( list_cpu_idx ); do {
                zram_dev="$( zram_dev "$core" )"
                zram_applicable "$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"
                echo $(( $zram_size * 1024 * 1024 )) >"/sys/block/$( basename $zram_dev )/disksize"
                mkswap "$zram_dev"
                swapon "$zram_dev"
        } done
}

stop()
{
        local zram_dev proc_entry

        for core in $( list_cpu_idx ); do {
                zram_dev="$( zram_dev "$core" )"
                proc_entry="/sys/block/$( basename "$zram_dev" )/reset"

                grep -sq ^"$zram_dev " /proc/swaps && {
                        logger -s -t zram_stop -p daemon.debug "deactivate swap $zram_dev"
                        swapoff "$zram_dev"
                }

                zram_reset "$zram_dev" "claiming memory back"
        } done
}