[gentoo-amd64] Re: I can use only 3GB aout of install 6GB

[Duncan]

Branko Badrljica <brankob@××××××××××.com> posted
4A01A58C.2040908@××××××××××.com, excerpted below, on  Wed, 06 May 2009
16:58:20 +0200:

> Duncan wrote:
>> Then, look at memory model.  Here, with current kernels, I have only
>> one option, Sparse.  However [some have the] Flat and Discontiguous
>> options as well.

> I thought those extra options were just for NUMA systems and were about
> how the memory from several NUMA nodes "fits together" ie whether it has
> to form one continuos memory range or not.

It's possible.  The documentation on them is a bit limited, and I may 
have inferred more than was justified from the fact that the options 
there were so similar to the ones in my BIOS that (seemed to) control the 
>4-gig memory layout.  It's also worth noting that I DO have a NUMA
system here, so my somewhat trial and error method of finding what worked 
for me included that factor as well, and I may have misattributed the 
effects.

Never-the-less, it was the two BIOS options and the two kernel options, 
that together I tweaked, until I came up with a config that gave me use 
of all of memory, the GART based IOMMU (without which I found I couldn't 
boot at all with >4 gig addressable memory, because my SIL_SATA PCI-X 
hardware and/or the kernel driver for it are evidently legacy-PCI and the 
kernel would halt trying to access the disk in DMA mode addressing above 
4G RAM), and NUMA.

Oh, something else I found didn't work, but this is a chipset specific 
errata I believe.  AGP fast-writes simply don't work on this system.  I 
had to disable them both in the BIOS and in xorg.conf.  That's something 
else people might want to watch for.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
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