Bug#295678: kernel-image packages with CONFIG_HIGHMEM64G=y enabled
On Wed, Aug 10, 2005 at 11:57:35AM +0900, Horms wrote:
> 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.
>
I can't say I'm a fan of adding another flavour. How many people are
actually using >4GB of memory on x86? I suspect (or hope) that people
who are going to be doing those sorts of things will be using x86_64
and ia64 hardware. Christian's problem, aiui, is simply that the kernel
sees 3.5GB instead of 4GB. I'm not sure whether this is by design, or is
a bug, but I'd much rather see that fixed instead.
Reply to: