Re: 2G memory split

[Jeff V. Merkey]

Jeff V. Merkey wrote:

> Linus Torvalds wrote:
>
> > On Tue, 10 Jan 2006, Martin Bligh wrote:
> >
> >
> > > The non-1GB-aligned ones need to be disbarred when PAE is on, I think.
> >
> > Well, right now _all_ the non-3:1 cases need to be disbarred. I think 
> > we depend on the kernel mapping only ever being the _one_ last entry 
> > in the top-level page table, which is only true with the 3:1 mapping.
> >
> > But I didn't check.
>
>
> No. It works fine (or seems to) with 2:2 mapping. I've tested with 
> these extensively
> and am shipping products on the 1U appliances with 2:2 and I have 
> never seen any problems
> with 2.6.9-2.6.13.
>
> The only unpleasant side affect with 3:1 is user apps seem to rely on 
> swap space
> a little more than I like -- perhaps this is the side affect you are 
> referring to?
>
> RH ES uses 4:4 which is ideal and superior to this hack.
>
> Jeff
Take that back. I checked the build and 2:2 does not work correctly with 
highmem enabled. So
you may be correct. Highmem support is crap anyway and a 4:4 scheme is 
what this should have been
from the start. It's ok. The nice thing about Linux if you don't like 
what Linus is cooking in the kitchen,
you can add your own ingredients and make something else.

Jeff
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