On 2/2/21 2:45 PM, Yang Shi wrote:

quoted

Should we keep it simple for now and only try to demote those pages that are
free of cpusets and memory policies?
Actually, demoting those pages to a CPU or a NUMA node that does not fall into
their set, would violate those constraints right?

Yes, this has been discussed since the very beginning. There is not an
easy way to figure out the memory placement policy (cpuset and
mempolicy) from "page". I think this also prevents "demote those pages
that are free of cpusets and memory policies".

The conclusion was the violation should be fine for now. And the
demotion feature is opt'ed in by a new node reclaim mode.

This has come up a couple of times.

I'll add a bit of changelog material about it in the last patch since
that's where the opt-in is introduced.