RE: [PATCH] RFC : Page table macros

From: Luck, Tony <tony.luck_at_intel.com>
Date: 2005-11-17 10:05:15
> 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.

This is perhaps a good point.  If someone ever wants to get 4-level
page tables running with 64K pagesize, they will want to allocate
less than a full page at one (or more) levels (since 13+13+13+13+16
is 68 ... more bits than we need).  So expressions like
       (4*PAGE_SHIFT - 9)
will reveal even more hidden assumptions.

However, I can't quite imagine a structure where the entries in
the _upper_ levels are anything except pointers (unless h/w is
walking the upper levels and imposes some other structure ... but
this is not the case for ia64).

-Tony
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Received on Thu Nov 17 10:05:54 2005

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