I would like to know which of both is faster; a tmpfs or a ext4 ramdisk.
If someone knows a good way to benchmark disk perfomance on ubuntu, I will gladly do the test myself and post the results.
For many file operations, they probably have approximately the same speed. If you have journaling turned on for the ext4 filesystem though, that might slow things down.
However, the main benefit of tmpfs is that it only uses as much RAM (or swap) as is needed to store the files. In contrast, a 500MB ramdisk will use that much RAM whether it is 10% full or 100% full.
tmpfs of course. It also avoids having to preallocate a fixed size of ram. One common disk benchmark is bonnie++.