I was reading up on a rather-dated article on the kernel managing memory and had this question on where the Page Table Entries (PTE) would go into.
For this example, the author assumes we are on a 32-bit machine with 4GB memory without PAE. The article assumes 3GB to be addressable as virtual memory (4KB pages of 3GB == 786,432 pages). But if there was a PTE of 4 bytes for each page, that in itself would account for ~3.1MB of memory which should be set aside by the kernel. Is this going to be a part of kernel memory? ie. kernel reserved memory apart from the user addressable 3GB?
So, does the kernel first calculate and arrive at how much kernel (system) memory would be needed and how much it can mark as user-addressable memory at boot?
What other stuff would reside in kernel/system-reserved memory?