Re: [PATCH] Fake NUMA emulation for PowerPC

[Kumar Gala <galak@kernel.crashing.org>]

On Dec 7, 2007, at 4:12 PM, Balbir Singh wrote:

> Kumar Gala wrote:
> > On Dec 7, 2007, at 3:35 PM, Balbir Singh wrote:
> >
> > > Olof Johansson wrote:
> > > > Hi,
> > > >
> > > > On Sat, Dec 08, 2007 at 02:44:25AM +0530, Balbir Singh wrote:
> > > >
> > > > > Comments are as always welcome!
> > > >
> > > > Care to explain what this is useful for? (Not saying it's a  
> > > > stupid idea,
> > > > just wondering what the reason for doing it is).
> > >
> > > In my case, I use it to test parts of my memory controller patches  
> > > on an
> > > emulated NUMA machine. I plan to use it to test out page migration
> > > across nodes.
> >
> > Can you explain that further.  I'm still not clear on why this is  
> > useful.
> >
> > - k
>
> Sure. In my case I need to emulate NUMA nodes to do some NUMA specific
> testing. The memory controller I've written has some interesting data
> structures like per node, per zone LRU lists. To be able to test those
> features on a non-numa box is a problem, since we get just the  
> default node.

Maybe I'm missing something, what do you mean by memory controller  
you've written?  (I'm use to the term 'memory controller' meaning the  
actual RAM control).

> To be able to test the memory controller under NUMA, I use fake NUMA
> nodes. x86-64 has a similar feature, the code I have here is the
> simplest I could come up with for PowerPC.
>
> I just thought of another very interesting use case, it can be used to
> split up the zone's lru lock which is highly contended.

- k
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