mkdir -p writebehind.tmp
cd writebehind.tmp

NR=100

if [ ! -d dummy ] ; then
	mkdir dummy
	for i in $(seq $NR) ; do
		size_kb=$[$RANDOM % 64 * 1024]
		dd if=/dev/zero of=dummy/$i bs=1024 count=$size_kb
	done
	sync -f .
fi

echo SIZE
du -sh dummy

for mode in 0 1 2; do
	sudo sysctl vm.dirty_write_behind=$mode

	echo COPY
	time time cp -r dummy copy

	grep Dirty /proc/meminfo

	echo SYNC
	time sync -f copy

	rm -fr copy
done