[PATCH v2 0/5] mm: demotion: Introduce new node state N_DEMOTION_TARGETS

[Jagdish Gediya <jvgediya@linux.ibm.com>]

Current implementation to find the demotion targets works
based on node state N_MEMORY, however some systems may have
dram only memory numa node which are N_MEMORY but not the
right choices as demotion targets.

This patch series introduces the new node state
N_DEMOTION_TARGETS, which is used to distinguish the nodes which
can be used as demotion targets, node_states[N_DEMOTION_TARGETS]
is used to hold the list of nodes which can be used as demotion
targets, support is also added to set the demotion target
list from user space so that default behavior can be overridden.

node state N_DEMOTION_TARGETS is also set from the dax kmem
driver, certain type of memory which registers through dax kmem
(e.g. HBM) may not be the right choices for demotion so in future
they should be distinguished based on certain attributes and dax
kmem driver should avoid setting them as N_DEMOTION_TARGETS,
however current implementation also doesn't distinguish any 
such memory and it considers all N_MEMORY as demotion targets
so this patch series doesn't modify the current behavior.

Current code which sets migration targets is modified in
this patch series to avoid some of the limitations on the demotion
target sharing and to use N_DEMOTION_TARGETS only nodes while
finding demotion targets.

Changelog
----------

v2:
In v1, only 1st patch of this patch series was sent, which was
implemented to avoid some of the limitations on the demotion
target sharing, however for certain numa topology, the demotion
targets found by that patch was not most optimal, so 1st patch
in this series is modified according to suggestions from Huang
and Baolin. Different examples of demotion list comparasion
between existing implementation and changed implementation can
be found in the commit message of 1st patch.

Jagdish Gediya (5):
  mm: demotion: Set demotion list differently
  mm: demotion: Add new node state N_DEMOTION_TARGETS
  mm: demotion: Add support to set targets from userspace
  device-dax/kmem: Set node state as N_DEMOTION_TARGETS
  mm: demotion: Build demotion list based on N_DEMOTION_TARGETS

 .../ABI/testing/sysfs-kernel-mm-numa          | 12 ++++
 drivers/base/node.c                           |  4 ++
 drivers/dax/kmem.c                            |  2 +
 include/linux/nodemask.h                      |  1 +
 mm/migrate.c                                  | 67 +++++++++++++++----
 5 files changed, 72 insertions(+), 14 deletions(-)

-- 
2.35.1