Re: PROBLEM: OOPSes in PREEMPT SMP for AMD Opteron Dual-Core with Memhole Mapping (non tainted kernel)

From: Jacob Martin
Date: Mon Jun 13 2005 - 19:00:14 EST


On Monday 13 June 2005 10:06 am, Andi Kleen wrote:
> On Sun, Jun 12, 2005 at 03:29:50PM -0400, Jacob Martin wrote:
> > Hardware memhole mapping never seems to work, or causes lockups right
> > away. I need to test it further though.
> >
> > I have discovered that with the following features enabled:
> >
> > 1. Software memhole mapping
> > 2. Continuous,
> >
> > linux sees the entire 4GB of memory. However, when things start getting
> > requested from the upper half, there are Oopses generated. Attached are
> > two Oopses that occurred under the test scenario described.
>
> What happens when you boot with numa=off or with numa=noacpi ?

You got it! It seems to be working just fine without it compiled into the
kernel.

> The system seems to believe it has memory in an area not covered
> by mem_map.

I think you hit it right on the head.

I enabled NUMA because I had anticipated upgrading later. So I guess if you
don't actually have NUMA set up hardware-wise, and enable this module, then
you will have problems.

Maybe a simple update to the kernel "K8 NUMA support" Processor feature's help
section should be made to note this? Or, is there something that could be
fixed somewhere. I wouldn't mind helping, it was baffling me for two weeks.

> > launch big memory apps.
> >
> > I suppose I could write a program to consume/probe the upper memory half.
> > Anyone know of a good/quicky way to do that?
>
> You can use the attached program which I often use for similar purposes.
> It writes nearly all free memory in a loop and also often triggers memory
> problems.

Thanks for that too!

Sincerely,
Jacob Martin


--
Jacob Martin
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