[v3,0/6] mm / virtio-mem: support ZONE_MOVABLE

Message

David Hildenbrand Aug. 4, 2020, 7:24 a.m. UTC

@Andrew can we give this a churn and consider it for v5.9 in case there
are no more comments?

Patch #1-#4 have RB's, patch #5 is virtio-mem stuff maintained by me,
patch #6 is just a doc update.

---

Currently, virtio-mem does not really support ZONE_MOVABLE. While it allows
to online fully plugged memory blocks to ZONE_MOVABLE, it does not allow
to online partially-plugged memory blocks to ZONE_MOVABLE and will never
consider such memory blocks when unplugging memory. This might be
surprising for users (especially, if onlining suddenly fails).

Let's support partially plugged memory blocks in ZONE_MOVABLE, allowing
partially plugged memory blocks to be online to ZONE_MOVABLE and also
unplugging from such memory blocks.

This is especially helpful for testing, but also paves the way for
virtio-mem optimizations, allowing more memory to get reliably unplugged.

Cleanup has_unmovable_pages() and set_migratetype_isolate(), providing
better documentation of how ZONE_MOVABLE interacts with different kind of
unmovable pages (memory offlining vs. alloc_contig_range()).

v2 -> v3:
- "mm: document semantics of ZONE_MOVABLE"
-- Fix a typo

v1 -> v2:
- "mm/page_isolation: don't dump_page(NULL) in set_migratetype_isolate()"
-- Move to position 1, add Fixes: tag
-- Drop unused "out:" label
- "mm/page_isolation: drop WARN_ON_ONCE() in set_migratetype_isolate()"
-- Keep curly braces on "else" case
- Replace "[PATCH v1 5/6] mm/page_alloc: restrict ZONE_MOVABLE optimization
           in has_unmovable_pages() to memory offlining"
  by "mm: document semantics of ZONE_MOVABLE"
-- Brain dump of what I know about ZONE_MOVABLE

David Hildenbrand (6):
  mm/page_isolation: don't dump_page(NULL) in set_migratetype_isolate()
  mm/page_alloc: tweak comments in has_unmovable_pages()
  mm/page_isolation: drop WARN_ON_ONCE() in set_migratetype_isolate()
  mm/page_isolation: cleanup set_migratetype_isolate()
  virtio-mem: don't special-case ZONE_MOVABLE
  mm: document semantics of ZONE_MOVABLE

 drivers/virtio/virtio_mem.c | 47 +++++++------------------------------
 include/linux/mmzone.h      | 34 +++++++++++++++++++++++++++
 mm/page_alloc.c             | 22 +++++------------
 mm/page_isolation.c         | 39 ++++++++++++++----------------
 4 files changed, 65 insertions(+), 77 deletions(-)