The post in question uses tmpfs, which means it uses a combination of ram and swap. You may want to look into ramfs instead as it only uses ram space. I would imagine the command is similar. You could also use ramdisk which creates a virtual device that you can apply a filesystem to and everything.

Sources:

"tmpfs will use swap space when neccessary"

source = https://stackoverflow.com/questions/7242484/can-i-over-run-the-tmpfs-size

"If you compare it to ramfs (which was the template to create tmpfs)
you gain swapping and limit checking."

source = www.kernel.org/doc/Documentation/filesystems/tmpfs.txt

"The memory used by tmpfs grows and shrinks to accommodate the files it contains and can be swapped out to swap space"

source = http://en.wikipedia.org/wiki/Tmpfs

"Tmpfs uses swap, where as Ramfs doesn't."

source = What is the difference between tmpfs and ramfs