mm/migrate: update node demotion order on hotplug events

Reclaim-based migration is attempting to optimize data placement in memory
based on the system topology.  If the system changes, so must the
migration ordering.

The implementation is conceptually simple and entirely unoptimized.  On
any memory or CPU hotplug events, assume that a node was added or removed
and recalculate all migration targets.  This ensures that the
node_demotion[] array is always ready to be used in case the new reclaim
mode is enabled.

This recalculation is far from optimal, most glaringly that it does not
even attempt to figure out the hotplug event would have some *actual*
effect on the demotion order.  But, given the expected paucity of hotplug
events, this should be fine.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Dave Hansen <[email protected]>
Signed-off-by: "Huang, Ying" <[email protected]>
Reviewed-by: Yang Shi <[email protected]>
Reviewed-by: Zi Yan <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Wei Xu <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Greg Thelen <[email protected]>
Cc: Keith Busch <[email protected]>
Cc: Yang Shi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions