Re: [PATCH 00/18] Make common x86 arch area for i386 and x86_64 -Take 2

[Martin Bligh]

Christoph Lameter wrote:
> On Fri, 16 Mar 2007, Martin Bligh wrote:
>
> > You have to do some sort of lookup anyway, and Andy seemed to have them
> > all folded into one.
>
> What lookup would you need to do? On x86_64 even the TLB use is 
> hidden by the existing 2M entries for 1-1 mappings.
>
> > Or are you trying to avoid this by going to back to the crud we had
> > in 2.4 where we pretend mem_map is one big array, indexed by pfn with
> > huge sparsely mapped holes in it?
>
> Yes that the advanced way of doing it rather than adding useless custom 
> lookups.

For starters, you can't do that sparse a mapping on a 32 bit system.
I'll let Andy explain the rest of it.

> > Would be nice to work out (and document somewhere) what the pros and
> > cons of virtual memmap vs sparsemem were - ISTR one of the arguments
> > was extremely sparsely layed out machines, and you needed sparsemem
> > for that. But right now we have 3 solutions, which is not a good
> > situation.
>
> Please read my posts to linux-mm on that subject. We discussed it last 
> year in detail and the agreement was that the sparsemem crud needs to be 
> taken out. Kame-san posted patches to do that.

"the agreement"? So Andy agreed to taking it out? Or you and Kame did?

M.


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