NUMA setup on Tyan s2895

[Lionel Elie Mamane <lionel@mamane.lu>]

Hi,

Still with my Tyan s2895, I have two CPUs and 4GB, made of 8*512MB
DIMM modules, of RAM. The motherboard's documentation clearly shows
that four memory slots (two banks) are attached to each CPU. See the
block diagram on page 2 of
ftp://ftp.tyan.com/datasheets/d_s2895_100.pdf .

What I find strange is the NUMA setup Linux reports:

 Scanning NUMA topology in Northbridge 24
 Number of nodes 2
 Node 0 MemBase 0000000000000000 Limit 000000007fffffff
 Node 1 MemBase 0000000080000000 Limit 000000015fffffff
 node 1 shift 24 addr ff000000 conflict 0
 Using node hash shift of 25
 Bootmem setup node 0 0000000000000000-000000007fffffff
 Bootmem setup node 1 0000000080000000-000000015fffffff
 On node 0 totalpages: 524287
   DMA zone: 4096 pages, LIFO batch:1
   Normal zone: 520191 pages, LIFO batch:31
   HighMem zone: 0 pages, LIFO batch:1
 On node 1 totalpages: 917503
   DMA zone: 0 pages, LIFO batch:1
   Normal zone: 917503 pages, LIFO batch:31
   HighMem zone: 0 pages, LIFO batch:1

How come it is so different: 917503 (a tad less than 3584MB) pages
versus 524287 (a tad less than 2GB)! I'd have expected an at least
roughly half-half split? Err... As I realise things, the addition of
the two is much more than my RAM. Would the PCI hole / mappings be
included herein?

More info on system:

master@capsaicin:~$ cat /proc/mtrr
reg00: base=0x00000000 (   0MB), size=2048MB: write-back, count=1
reg01: base=0x100000000 (4096MB), size=1024MB: write-back, count=1
reg02: base=0x140000000 (5120MB), size= 512MB: write-back, count=1
reg03: base=0x80000000 (2048MB), size= 512MB: write-back, count=1

and

BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 0000000000096400 (usable)
 BIOS-e820: 0000000000096400 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000c2000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 000000009ff20000 (usable)
 BIOS-e820: 000000009ff20000 - 000000009ff2d000 (ACPI data)
 BIOS-e820: 000000009ff2d000 - 000000009ff80000 (ACPI NVS)
 BIOS-e820: 000000009ff80000 - 00000000a0000000 (reserved)
 BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
 BIOS-e820: 00000000fec00000 - 00000000fec00400 (reserved)
 BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
 BIOS-e820: 00000000fff80000 - 0000000100000000 (reserved)
 BIOS-e820: 0000000100000000 - 0000000160000000 (usable)


-- 
Lionel