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

[Christoph Lameter]

On Mon, 2 Apr 2007, Andi Kleen wrote:

> > No no no. For the gazillions time: All of 1-1 mapped kernel memory on 
> > x86_64 needs a 2 MB page table entry. The virtual memmap uses the same. 
> > There are *no* additional TLBs used.
> 
> But why do you reserve an own virtual area then if you claim to not use any
> additional mappings? 

The 1-1 area using mappings for 2MB pages right? So it uses a virtual 1-1 
area. It already has a virtual mapping.

What we do for virtual memmap here is also use 2MB pages but order the 
pages a bit different so that they provide a linear memory map.

So the number of TLBs in use stays the same. There are a few additional 
higher level page table pages that are needed to provide the alternate 
view that generates the linear mapping but that is just a couple of pages.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/