Re: 3.1-rc2: CONFIG_NUMA Question

[David Rientjes]

On Thu, 18 Aug 2011, Justin Piszcz wrote:

> > The max of NUMA nodes is specified by CONFIG_NODES_SHIFT,
> > in your case, it is 6, which means it supports up to 2^6 nodes.
> Ok, is there any overhead having more than is needed?
> 

Yeah, try to avoid going above 8 because that causes nodemasks that are 
typically allocated on the stack of kernel text to be dynamically 
allocated through the slab allocator to avoid the possibility of overflow.  
I doubt you have the need for more than 64 nodes, so I'd highly recommend 
leaving it at the default unless you want to debug or test some large 
numa=fake settings.
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