[Discuss] Limiting amount of memory

[bogstad at pobox.com (Bill Bogstad)]

On Fri, Sep 13, 2013 at 10:10 PM, Richard Pieri <richard.pieri at gmail.com> wrote:
> Bill Bogstad wrote:
>>
>> It would still be nice to know where the memory is being used.
>
>
> Some Googling about lead me to the PCI memory hole:
> http://en.wikipedia.org/wiki/PCI_hole

Thanks.   I've read it now.

>...
> As to why mem=16G leaves the system with only 9GB detected? Dunnow. If
> mem=8G yields ~6GB useable then mem=16G should yield ~14GB usable on that
> box. There could be some kind of memory mapping weirdness between the PCI
> allocations and the kernel RAM constraints.

Ahh the kernel does figure into this. :-)   Particularily since losing
6G when the entire 32-bit PCI space is only 4G does seem a bit odd.
I also can't imagine that people buying Windows servers would be happy
to see 38% of the RAM they purchased (6G/16G) just disappear.   Maybe
Windows and the BIOS have some way to communicate about memory
availability that Linux doesn't understand.   I would call that a bug
(or at least a deficiency) in Linux.

Bill Bogstad