On Wed 18-03-20 19:20:41, Cristopher Lameter wrote:

On Wed, 18 Mar 2020, Srikar Dronamraju wrote:

quoted

For a memoryless or offline nodes, node_numa_mem refers to a N_MEMORY
fallback node. Currently kernel has an API set_numa_mem that sets
node_numa_mem for memoryless node. However this API cannot be used for
offline nodes. Hence all offline nodes will have their node_numa_mem set
to 0. However systems can themselves have node 0 as offline i.e

That is a significant change to the basic assumptions for memory less
nodes. Node 0 needed to have memory and processors. Not sure what else
may break.

This assumption is simply incorrect. There many examples but just
one from top of my head 3e8589963773 ("memcg: make it work on sparse
non-0-node systems"). We simply have to forget that some nodes are
special.
-- 
Michal Hocko
SUSE Labs