Re: [RFC, PATCHv1 00/28] 5-level paging

From: Andi Kleen
Date: Fri Dec 09 2016 - 11:40:17 EST

> On other hand, large virtual address space would put more pressure on
> cache -- at least one more page table per process, if we make 56-bit VA
> default.

The top level page always has to be there unless you disable it at boot time
(unless you go for a scheme where some processes share top level pages, and
others do not, which would likely be very complicated)

But even with that it is more than one: A typical set up has at least two extra
4K pages overhead, one for the bottom and one for the top mappings. Could easily be