Re: pte_addr_t size reduction for 64 GB case?

[William Lee Irwin III]

Albert Cahalan <albert@xxxxxxxxxxxxxxxxxxxxx> wrote:
>> When handling 64 GB on i386, pte_addr_t really only
>> needs 33 bits to find the PTE. It sure doesn't need
>> the full 64 bits it is using.

On Wed, May 19, 2004 at 12:44:24AM -0700, Andrew Morton wrote:
> yup.

Albert Cahalan <albert@xxxxxxxxxxxxxxxxxxxxx> wrote:
>> How about cheating a bit? If the pte_addr_t only had
>> the high 32 bits of the 36-bit pointer, it would point
>> to a pair of the 8-byte PTEs in a 16-byte chunk of RAM.
>> Then simply examine the PTEs to see which one is the
>> correct one.

On Wed, May 19, 2004 at 12:44:24AM -0700, Andrew Morton wrote:
> They might both map the same page.  It could overflow into page->flags.

An overflow area for the 33rd bits in pte_chains is another idea. A
CONFIG_HIGHMEM32G is another. But Hugh's and/or Andrea's code sounds
nicer than either of those. It doesn't get smaller than 0.

-- wli
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