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SubjectRe: [patch 2/2] enables booting a NUMA system where some nodes have no memory
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On Wed, 2006-11-15 at 14:41 -0800, Christoph Lameter wrote:
> On Wed, 15 Nov 2006, Martin Bligh wrote:
>
> > A node is an arbitrary container object containing one or more of:
> >
> > CPUs
> > Memory
> > IO bus
> >
> > It does not have to contain memory.
>
> I have never seen a node on Linux without memory. I have seen nodes
> without processors and without I/O but not without memory.This seems to be
> something new?

I sent this out earlier in response to another message from Christoph
regarding nodes w/o memory. Don't know if it made it...

>On Fri, 2006-11-10 at 10:16 -0800, Christoph Lameter wrote:
>> On Wed, 8 Nov 2006, KAMEZAWA Hiroyuki wrote:
>>
>> > I wonder there are no code for creating NODE_DATA() for
device-only-node.
>>
>> On IA64 we remap nodes with no memory / cpus to the nearest node
with
>> memory. I think that is sufficient.

I don't think this happens anymore. Back in the ~2.6.5 days, when we
would configure our numa platforms with 100% of memory interleaved [in
hardware at cache line granularity], the cpus would move to the
interleaved "pseudo-node" and the memoryless nodes would be removed.
numactl --hardware would show something like this:

# uname -r
2.6.5-7.244-default
# numactl --hardware
available: 1 nodes (0-0)
node 0 size: 65443 MB
node 0 free: 64506 MB

I started seeing different behavior about the time SPARSEMEM went in.
Now, with a 2.6.16 base kernel [same platform, hardware interleaved
memory], I see:

# uname -r# numactl --hardware
available: 5 nodes (0-4)
node 0 size: 0 MB
node 0 free: 0 MB
node 1 size: 0 MB
node 1 free: 0 MB
node 2 size: 0 MB
node 2 free: 0 MB
node 3 size: 0 MB
node 3 free: 0 MB
node 4 size: 65439 MB
node 4 free: 64492 MB
node distances:
node 0 1 2 3 4
0: 10 17 17 17 14
1: 17 10 17 17 14
2: 17 17 10 17 14
3: 17 17 17 10 14
4: 14 14 14 14 10
2.6.16.21-0.8-default

[Aside: The firmware/SLIT says that the interleaved memory is closer to
all nodes that other nodes' memory. This has interesting implications
for the "overflow" zone lists...]

Lee

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