zram (previously called compcache) can create RAM based block devices. It is an experimental (staging) module of the Linux kernel since 3.2.
Background information
Startup script
Copy the following script to /etc/init.d/zram:
### BEGIN INIT INFO # Provides: zram # Required-Start: $local_fs # Required-Stop: $local_fs # Default-Start: S # Default-Stop: 0 1 6 # Short-Description: Use compressed RAM as in-memory swap # Description: Use compressed RAM as in-memory swap ### END INIT INFO # Author: Antonio Galea <antonio.galea@gmail.com> # Thanks to Przemysław Tomczyk for suggesting swapoff parallelization FRACTION=75 MEMORY=`perl -ne'/^MemTotal:\s+(\d+)/ && print $1*1024;' < /proc/meminfo` CPUS=`grep -c processor /proc/cpuinfo` SIZE=$(( MEMORY * FRACTION / 100 / CPUS )) case "$1" in "start") param=`modinfo zram|grep num_devices|cut -f2 -d:|tr -d ' '` modprobe zram $param=$CPUS for n in `seq $CPUS`; do i=$((n - 1)) echo $SIZE > /sys/block/zram$i/disksize mkswap /dev/zram$i swapon /dev/zram$i -p 10 done ;; "stop") for n in `seq $CPUS`; do i=$((n - 1)) swapoff /dev/zram$i && echo "disabled disk $n of $CPUS" & done wait sleep .5 modprobe -r zram ;; *) echo "Usage: `basename $0` (start | stop)" exit 1 ;; esac
then you may have to make the script executable:
chmod +x /etc/init.d/zram
then instruct your system to start it at boot time, with the command
insserv zram