Dean Kent (dkent@realworldtech.com) on 5/14/07 wrote:
>Isn't this a different issue (or a tangential one, at least) to what was being
>discussed? The statement being made (or so I understood it) was that the address
>space had to map all possible memory addresses, so a machine with 1GB of memory
>would necessarily have every address space mapped to 2GB. My understanding is that
>you only allocate pages of virtual memory for what is needed to hold the program/data,
>and add them as necessary as the working set size grows - is this not a correct understanding?

Yeah, I think Linus misread you and answered the wrong question.
The Linux kernel likes to map the entire physical memory into the kernel virtual address space and gains simplicity and performance from it.
However, it also works fine without it.