Re: Why preallocate pmd in x86 32-bit PAE?

[Jeremy Fitzhardinge]

Linus Torvalds wrote:
> So don't do it. Just preallocate for the magic 4-entry PGD. You can make 
> the special case just be something like
>   

Yes, OK, it makes sense.  Conceptually they would be dynamically
allocated and freed, but they'd just happen to start allocated, to avoid
the tlb flush of populating the pgd of an active pagetable.  If you
happened to do a 1G munmap, it may end up freeing and reallocating them,
but that's going to be very rare.  Either way, the other special cases
are avoided (though pgd_populate would still need to be correct, on the
offchance it gets invoked).

    J
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