Re: [PATCH 1/4] x86_64: Switch to SPARSE_VIRTUAL

Christoph Lameter
2007-04-02T22:37:58Z

On Tue, 3 Apr 2007, Andi Kleen wrote:

> If it works I would be inclined to replaced old sparsemem with Christoph's
> new one on x86-64. Perhaps that could cut down the bewildering sparsemem
> ifdef jungle that is there currently.
>
> But I presume it won't work on 32bit because of the limited address space?

Not in general but it will work in non PAE mode. 4GB need 2^(32-21+4) =
16MB pages. This would require the mapping on 4 4MB pages.

For 64GB you'd need 256M which would be a quarter of low mem. Probably
takes up too much of low mem.

> > But, without some cold, hard, data, we mere mortals without the 1024-way
> > machines can only guess. ;)
>
> Yep.
>
> -Andi (who would be scared of a 1024 way x86 machine)

- Christoph (who does not believe that Andi has to wait long for
something bigger)