On 4/10/19 8:56 PM, Yang Shi wrote:
When demoting to PMEM node, the target node may have memory pressure,This seems like an actively bad idea to me.
then the memory pressure may cause migrate_pages() fail.
If the failure is caused by memory pressure (i.e. returning -ENOMEM),
tag the node with PGDAT_CONTENDED. The tag would be cleared once the
target node is balanced again.
Check if the target node is PGDAT_CONTENDED or not, if it is just skip
demotion.
Why do we need an *active* note to say the node is contended? Why isn't
just getting a failure back from migrate_pages() enough? Have you
observed this in practice?