[PATCH v6 00/10] Implement numa node notifier

Oscar Salvador
2025-06-09T09:22:05Z

v5 -> v6:
- Remove redundant checks (per David)
- Fix build failure
- Drop 'nid' parameter from memory notify (Per David)
- Add RB/ACKs-by

v4 -> v5:
- Split out conversion for different consumers (per David)
- Renamed node-notifier actions (per David)
- Added new Documentation for new node-notifier and updated
the memory-notifier one to reflect the changes
- Make sure we do not trigger anything when !CONFIG_NUMA (per David)

v3 -> v4:
- Fix typos pointed out by Alok Tiwari
- Further cleanups suggested by Vlastimil
- Add RBs-by from Vlastimil

v2 -> v3:
- Add Suggested-by (David)
- Replace last N_NORMAL_MEMORY mention in slub (David)
- Replace the notifier for autoweitght-mempolicy
- Fix build on !CONFIG_MEMORY_HOTPLUG

v1 -> v2:
- Remove status_change_nid_normal and the code that
deals with it (David & Vlastimil)
- Remove slab_mem_offline_callback (David & Vlastimil)
- Change the order of canceling the notifiers
in {online,offline}_pages (Vlastimil)
- Fix up a couple of whitespaces (Jonathan Cameron)
- Add RBs-by

Memory notifier is a tool that allow consumers to get notified whenever
memory gets onlined or offlined in the system.
Currently, there are 10 consumers of that, but 5 out of those 10 consumers
are only interested in getting notifications when a numa node changes its
memory state.
That means going from memoryless to memory-aware of vice versa.

Which means that for every {online,offline}_pages operation they get
notified even though the numa node might not have changed its state.
This is suboptimal, and we want to decouple numa node state changes from
memory state changes.

While we are doing this, remove status_change_nid_normal, as the only
current user (slub) does not really need it.
This allows us to further simplify and clean up the code.

The first patch gets rid of status_change_nid_normal in slub.
The second patch implements a numa node notifier that does just that, and have
those consumers register in there, so they get notified only when they are
interested.

The third patch replaces 'status_change_nid{_normal}' fields within
memory_notify with a 'nid', as that is only what we need for memory
notifer and update the only user of it (page_ext).

Consumers that are only interested in numa node states change are:

- memory-tier
- slub
- cpuset
- hmat
- cxl
- autoweight-mempolicy

Oscar Salvador (10):
mm,slub: Do not special case N_NORMAL nodes for slab_nodes
mm,memory_hotplug: Remove status_change_nid_normal and update
documentation
mm,memory_hotplug: Implement numa node notifier
mm,slub: Use node-notifier instead of memory-notifier
mm,memory-tiers: Use node-notifier instead of memory-notifier
drivers,cxl: Use node-notifier instead of memory-notifier
drivers,hmat: Use node-notifier instead of memory-notifier
kernel,cpuset: Use node-notifier instead of memory-notifier
mm,mempolicy: Use node-notifier instead of memory-notifier
mm,memory_hotplug: Drop status_change_nid parameter from memory_notify

Documentation/core-api/memory-hotplug.rst | 76 ++++++--
.../zh_CN/core-api/memory-hotplug.rst | 3 -
drivers/acpi/numa/hmat.c | 8 +-
drivers/base/node.c | 21 +++
drivers/cxl/core/region.c | 16 +-
drivers/cxl/cxl.h | 4 +-
include/linux/memory.h | 2 -
include/linux/node.h | 40 +++++
kernel/cgroup/cpuset.c | 2 +-
mm/memory-tiers.c | 19 +-
mm/memory_hotplug.c | 165 ++++++++----------
mm/mempolicy.c | 13 +-
mm/page_ext.c | 16 +-
mm/slub.c | 60 ++-----
14 files changed, 238 insertions(+), 207 deletions(-)

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2.49.0