Re: [PATCH] RFC : Page table macros

From: Ian Wienand <ianw_at_gelato.unsw.edu.au>
Date: 2005-11-17 09:41:33
On Wed, Nov 16, 2005 at 02:29:27PM -0800, Chen, Kenneth W wrote:
> It may make sense for the pte level, but I don't see any value being added
> at pgd, pud, and pmd level.  Nobody knows on top of their head what is
> PMD_ENTRY_BITS.  One can grep, but that's my point, why should someone do
> the extra grep in order to find out that size of a pointer is 3?  One
> already know.

Well, therein lies my point.  Is it the size of a pointer or is it the
size of a pte/middle/uppper/global directory entry?  Yes, it is just
terminology; but if you're talking about "size of a blah directory
entry" and you have that size defined in pgtable.h, I think it is
better to use that definition in your assembly rather than refer to
it in some way that generates the same code but has slightly different
meaning.

The 4 level page table case where things have been left as
(4*PAGE_SHIFT - 9) I think shows that abstracting to think about
things as entries rather than as pointers is useful.

-i

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Received on Thu Nov 17 09:42:18 2005

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