Re: PTE --> 2 values??

[William Lee Irwin III]

On Sun, Nov 23, 2003 at 11:50:15PM -0500, John Smith wrote:
> I saw that Linux is using a 3 level page tables, pgd, pmd and pte. The value
> in the pte can refer to an actual page in memory OR an address on the swap
> device. How does the kernel distinguish the two values such that if the
> value is refering to an swap device address, it will not lookup the address
> in memory ??

There is a present bit. All other bits are available to the OS when the
present bit says "not present". On many machines, Linux' 3-level tree is
a pure software construct, and the processor is informed of translations
in other ways (e.g. inverted pagetables, direct TLB insertion).


-- wli
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