Re: [kernel-reviewers] a small code review (2414483) Automated g4 rollback of changelist 2396062.

[Andi Kleen <ak@suse.de>]

Martin Bligh <mbligh@google.com> writes:

> Tim Hockin wrote:
> > On Wed, Apr 26, 2006 at 10:12:14AM -0700, Ken Harrenstien wrote:
> >
> >>That doesn't work because IIRC it only reports the amount of memory
> >>the kernel has been told (eg via "mem=") to manage in a certain sense,
> >>not how much is actually physically available.
> >>
> >>The I2 netboot kernel would really REALLY like some exported /proc
> >>values that accurately report physical memory (if nothing else, the
> >>number of DIMMs and their sizes).  It has to figure this out in order
> >>to install the proper kernel with proper LILO command-line args.
> > The kernel can't really know how much memory is in the system without
> > getting chipset-specific.
> > MTRR is a good way to hazard a guess, and will probably be right,
> > but as
> > you indicated, BIOS vendors have historically been REALLY bad about
> > MTRRs.  Better now, but bad a few years ago.
> > SMBIOS (on our boards) *does* accurately report the number of DIMMS
> > and
> > their sizes (and more!).  But it only works on Google BIOS.

Actually quite a lot of SMBIOS report DIMMs more or less correct.
It works even on my laptop.

I implemented support for it in the latest mcelog (--dmi). Not all
and a few big names screw it up (in particular the mappings from
address range to interleave set). But overall it looks surprisingly
good so far. 

-Andi