Re: [RFC][PATCH 0/10] alternate 4-level page tables patches

[Andi Kleen <ak@suse.de>]

On Wed, Dec 22, 2004 at 10:19:09PM +1100, Nick Piggin wrote:
> But the advantages I see in the source code are a) pud folding matches 
> exactly
> how pmd folding was done on 2 level architectures, and b) it doesn't touch
> either of the "business ends" of the page table structure (ie. top most or
> bottom most levels).  I think these two points give some (if only slight)
> advantage in maintainability and consistency.

Sure, but when it's merged then pml4_t (or p<whatever>_t) would be 
the "business end", so it doesn't make much difference longer term.
After all future linux coders will not really care what was in the
past, just what is in the code at the time they hack on it.


> If I can get the bulk of the architectures changed and tested, the arch
> maintainers don't kick up too much fuss, it has a relatively trouble free 
> run
> in -mm, and Andrew and Linus are still happy to merge before 2.6.11, would 
> you
> be OK with the pud version (in principle)?

I can't say I'm very enthusiastic about it (but more due to scheduling
issues than technical issues). I don't see anything wrong with them by itself,
but I also don't think they have any particular advantages over the
pml4 version. But in the end the main thing I care about is that
4 level pagetables get in in some form, where exactly the
new level is added and how it is named is secondary.

I would prefer if it happened sooner though because the work
is not finished (the optimized walking is still needed),
and i've been just waiting for getting merged and settled
down a bit before continuing. 

-Andi

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