Re: [RFC PATCH 0/5] Use an alternative to _PAGE_PROTNONE for _PAGE_NUMA v2

[Linus Torvalds]

On Wed, Apr 9, 2014 at 4:34 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
>
> How painful would it be to get rid of _PAGE_NUMA entirely?  Page bits
> are a highly precious commodity and saving one would be valuable.

I don't think _PAGE_NUMA is a problem. It's only set when the page is
not present, so we have tons of bits then.

Now, that's still inconvenient for the 32-bit pte case, because we do
*not* have tons of bits for non-present cases since we need them for
the swap indexes.

This is different from _PAGE_SOFT_DIRTY, which we do need for both
present and swapped-out entries.

Or am I missing something?

            Linus
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