zram Usage as Default in Debian (?)

[Rainer Dorsch <ml@bokomoko.de>]

Hello,

I recently setup zram (for compressed swap space in RAM) on an older low RAM  
machine. I was quite happy with the result and started now to do the same 
setup also on my other machines. I am wondering if anybody is investigating, 
if debian should do that by default when installing a new machine or even 
better also when machines get upgraded.

Here is what I did:

(see http://crunchbanglinux.org/forums/post/150355/#p150355 for more details)

/etc/modules: add zram

add (num_devices=<number cpu cores>)
rd@blackbox:~$ cat /etc/modprobe.d/zram.conf
options zram num_devices=2
rd@blackbox:~$ 

/etc/init.d/zram
#!/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

start() {
    # get the number of CPUs
    num_cpus=$(grep -c processor /proc/cpuinfo)
    # if something goes wrong, assume we have 1
    [ "$num_cpus" != 0 ] || num_cpus=1

    # set decremented number of CPUs
    decr_num_cpus=$((num_cpus - 1))

    # get the amount of memory in the machine
    mem_total_kb=$(grep MemTotal /proc/meminfo | grep -E --only-matching 
'[[:digit:]]+')
    mem_total=$((mem_total_kb * 1024))

    # load dependency modules
    modprobe zram num_devices=$num_cpus

    # initialize the devices
    for i in $(seq 0 $decr_num_cpus); do
    echo $((mem_total / num_cpus)) > /sys/block/zram$i/disksize
    done

    # Creating swap filesystems
    for i in $(seq 0 $decr_num_cpus); do
    mkswap /dev/zram$i
    done

    # Switch the swaps on
    for i in $(seq 0 $decr_num_cpus); do
    swapon -p 100 /dev/zram$i
    done
}

stop() {
    # get the number of CPUs
    num_cpus=$(grep -c processor /proc/cpuinfo)

    # set decremented number of CPUs
    decr_num_cpus=$((num_cpus - 1))

    # Switching off swap
    for i in $(seq 0 $decr_num_cpus); do
    if [ "$(grep /dev/zram$i /proc/swaps)" != "" ]; then
    swapoff /dev/zram$i
    sleep 1
    fi
    done

    sleep 1
    rmmod zram
}

case "$1" in
    start)
        start
        ;;
    stop)
        stop
        ;;
    restart)
        stop
        sleep 3
        start
        ;;
    *)
        echo "Usage: $0 {start|stop|restart}"
        RETVAL=1
esac
exit $RETVAL


################END##############

# update-rc.d zram defaults

Thanks,
Rainer
-- 
Rainer Dorsch
http://bokomoko.de/