Re: [PATCH] Fake NUMA emulation for PowerPC

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

Kumar Gala wrote:

quoted

On Dec 7, 2007, at 3:35 PM, Balbir Singh wrote:

quoted

Olof Johansson wrote:

quoted

Hi,

On Sat, Dec 08, 2007 at 02:44:25AM +0530, Balbir Singh wrote:

quoted

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