Sorry, I don't buy that.

a) It does not need to be architecture neutral.  

b) You surely need a way of communicating the discovered topology
   to userspace anyway.

c) $EDITOR /etc/numa-layouf.conf

d) $EDITOR /etc/kswapd.conf

I guess you could do that, but it seems overly complicated to me.
  

quoted

I think mbligh recently got the long-needed arch code in
for cpu to node... But I'm just not able to make the leap of faith that
memory detection is something that can ever comfortably be given to
userspace.

A simple syscall which alows you to launch a kswapd instance against
a group of zones on any group of CPUs provides complete generality 
and flexibility to userspace.  And it is architecture neutral.

If it really is incredibly hard to divine the topology from userspace
then you need to fix that up.  Provide the topology to userspace.
Which has the added benefit of providing, umm, the topology to userspace ;)

Can we make a simple default of 1 per node, which is what 99% 
of people want, and then make it more complicated later if people 
complain? It's really pretty easy:

for (node = 0; node < numnodes; ++node) {
	kswapd = kick_off_kswapd_for_node(node);
	kswapd->cpus_allowed = node_to_cpus(node);
}

Or whatever the current cpus_allowed method is. All we seem to need
is node_to_cpus ... I can give that to you tommorow with no problem,
it's trivial.

M.

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