Please help with following NUMA-related questions

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To: linux-kernel@vger.kernel.org
Date:	Mon, 25 Jul 2005 06:47:31 -0700

I will greatly appreciate any help regarding the following matters:

(1) How to know whether my machine is NUMA-aware or not,

(2) Difference between memory bank interleaving and node interleaving

(3) When the BIOS asks me to set bank interleaving as AUTO, then it says that
AUTO allows memory access to spread out over banks on the same node or across
nodes decreasing memory access contentions. However, I have no idea when the
memory access is spread over banks on the same node or across nodes. I also
do not know how to tell the machine to access memory across the nodes or on
the same node. I have no idea as to how the AUTO choice affects
NUMA-awareness.

(4) The BIOS also tells me that I could choose bani interleaving as DISABLED.
But I do not know what its implications are for NUMA awareness.

Here are other relevant details. I have a dual-Opteron 250 (2.4GHz) set in
Tyan Thunder 2885 K8W with AMIBIOS version 2.05.

When I bought it last year, the machine was running under SuSE 9.1 Pro and the
Linux kernel was 2.6.5-7.108-smp. At that time both the Hardware Info from
YAST and /vat/log/messages were explicitly mentioning things :

Scanning NUMA topology in Northbridge 24
  <6>Number of nodes 2 (10010)
  <6>Node 0 MemBase 0000000000000000 Limit 000000007fffffff
  <6>Node 1 MemBase 0000000080000000 Limit 00000000cbff0000
  <6>Using node hash shift of 24

These messages indicated that NODE interleaving was off and the machine was
NUMA-aware.

Then, after a few months, the motherboard failed and the machine was sent to
the vendor for repair. It came back with SuSE 9.3 and the Linux kernel
version 2.6.11.4-21.7-smp (geeko@buildhost) (gcc version 3.3.5 20050117
(prerelease) (SUSE Linux)) #1 SMP Thu Jun 2 14:23:14 UTC 2005.

Now both the Hardware Info from YAST and /vat/log/messages DO NOT mention
NUMA anywhere, and I do not have anyway to check whether the
NODE-Interleaving is OFF or ON. My difficulties are compounded because I do
not know how to interpret the chipset related setting in the BIOS.

Currently, in the BIOS setting (Chipset->memory config -> Bank Interleaving),
I am asked to choose between AUTO & DISABLED. No choice is offered for Node
Interleaving.

The only guidance for the choice is that interleaving allows memory access to
spread out over banks on the same node or across nodes decreasing memory
access contentions. Nothing is mentioned about what happens when Interleaving
is disabled. Furthermore, if I choose AUTO, then I do not know when the
memory is spread out over banks on the same node or across nodes.

Any help will be greatly appreciated.

Thanking you in advance.

-- 
Best regards.
Sheo
(Sheo S. Prasad)
Creative Research Enterprises
6354 Camino del Lago
Pleasanton, CA 94566, USA
Voice Phone: (+1) 925 426-9341
Fax   Phone: (+1) 925 426-9417
e-mail: ssp@CreativeResearch.org
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