Re: [Bugme-new] [Bug 2019] New: Bug from the mm subsystem involving X (fwd)

[Martin J. Bligh]

--Andi Kleen <ak@xxxxxxx> wrote (on Saturday, February 07, 2004 04:54:03 +0100):

> "Martin J. Bligh" <mbligh@xxxxxxxxxxx> writes:
>  
>> If we really want to do good testing, we should make a fake NUMA config
>> that can run a 4x SMP box as fake NUMA, with half the memory in each
>> "node" and half the processors ... but I never got around to coding that ;-)
> 
> I have such a patch for x86-64 if anybody is interested in that.
> 
> x86-64 low level NUMA is quite different from IA32 NUMA though so it 
> would be a bit difficult to port.

Not quite sure what you mean ... I was driving at pretending an SMP box
was NUMA ... but the x86_64 is already NUMA ... are you grouping nodes
together into single nodes with 2 cpus each?

What might be intriguing is to use Nick's domains stuff to create a heirarchy
for the scheduler where we have 1 cpu nodes and 2 cpu nodes above that, but
still keep the normal NUMA stuff flat for mem allocation. What might be 
interesting is a heirarchy where if this is the HT connections of cpu layouts:

1 --- 2
|     |
|     | 
|     |
3 --- 4

then domains of (1,2,3) (2,3,4) (1,3,4) (1 2 4), with a view to restricting
the "double hop" traffic as much as possible. But I'm not sure the domains
code copes with multiple overlapping domains - Nick?

Andi, do you already set up the mem allocation fallback zonelists like that?

M.

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