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
