This article says that Linux uses three-level page tables.
However, in the book Professional Linux Kernel Architecture, in chapter 3.3.1, it says that Linux uses five-level page tables.
Also, this article says ' The merging of five-level page tables (outside of the merge window) for 4.11-rc2, instead, barely raised an eyebrow.'
My question is how many page table levels does Kernel actually use? If it changed in the history, which version?