[Discuss] Limiting amount of memory

[tmcallaghan at gmail.com (Tim Callaghan)]

I really appreciate everyones feedback on this.  I'll do some more
experiments next week, what's most important to me is that I can create a
box that has 8G and 16G usable, I'll just have to do reboots to find out
what the correct mem= is for each.

-Tim



On Fri, Sep 13, 2013 at 11:50 PM, Bill Bogstad <bogstad at pobox.com> wrote:

> 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
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