Bug#295678: kernel-image packages with CONFIG_HIGHMEM64G=y enabled

[Horms <horms@debian.org>]

On Tue, Aug 09, 2005 at 05:34:33PM -0600, dann frazier wrote:
> On Tue, 2005-08-09 at 11:29 +0200, Christian Hammers wrote:
> > Hello
> > 
> > The problems is not Dell PowerEdge specific. My TYAN Tiger-i7320-S5350
> > (standard dual xeon server from www.ipc2u.com) also reports only 3.5GB 
> > after booting the Sarge 2.6 kernel :-( The BIOS reports full 4GB.
> > So if it does not hurt anybody I suggest turning on 64GB support.
> 
> >From arch/i386/Kconfig:
> 
>     If more than 4 Gigabytes is used then answer "64GB" here. This
>     selection turns Intel PAE (Physical Address Extension) mode on.
>     PAE implements 3-level paging on IA32 processors. PAE is fully
>     supported by Linux, PAE mode is implemented on all recent Intel
>     processors (Pentium Pro and better). NOTE: If you say "64GB" here,
>     then the kernel will not boot on CPUs that don't support PAE!
> 
> So it looks like this would hurt other users.  And, on machines that do
> support PAE, I've seen benchmarks that demonstrate a significant
> performance loss.  However, this was on a 2.4.25 kernel, not a recent
> 2.6, and I no longer have a link to those results - google might.
> 
> I think supporting these machines would mean adding an additional x86
> kernel-image flavor.

I think if it is a performance hit (on a sufficiently prevalent
set of hardware) then a new flavour would be in order.

On the machines not booting front, it seems those machines
are probably going to be using the 383 or 586 flavours rather
than the 686 flavour, so adding this option to the latter
shouldn't cause those machines to stop booting.

-- 
Horms