On Mon, Feb 01, 2021 at 11:13:14AM -0800, Dave Hansen wrote:

Sure.  Were you thinking of a code comment, or enhanced changelog?

Let's say there's a system with two sockets each with the same three
classes of memory: fast, medium and slow.  Each memory class is placed
in its own NUMA node and the CPUs are attached to the fast memory.  That
leaves 6 NUMA nodes (0-5):

	Socket A: 0, 1, 2
	Socket B: 3, 4, 5

The migration path for this configuration path would start on the nodes
with the processors and fast memory, progress through medium and end
with the slow memory:

	0 -> 1 -> 2 -> stop
	3 -> 4 -> 5 -> stop

This is represented in the node_demotion[] like this:

	{  1, // Node 0 migrates to 1
	   2, // Node 1 migrates to 2
	  -1, // Node 2 does not migrate
	   4, // Node 3 migrates to 1
	   5, // Node 4 migrates to 2
	  -1} // Node 5 does not migrate

Is that what you were thinking of?

I would not mind to have the above explanation in a comment somewhere
in the code.


-- 
Oscar Salvador
SUSE L3