path: root/Documentation/admin-guide
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authorPavel Tatashin <>2021-05-04 18:39:12 -0700
committerLinus Torvalds <>2021-05-05 11:27:26 -0700
commitfa965fd54827a6b6967602051736da9c163b79b7 (patch)
tree2b4ea2a772f199616315d326c8063b8483579731 /Documentation/admin-guide
parentd1e153fea2a8940273174fc17733c44323d35cd5 (diff)
memory-hotplug.rst: add a note about ZONE_MOVABLE and page pinning
Document the special handling of page pinning when ZONE_MOVABLE present. Link: Signed-off-by: Pavel Tatashin <> Suggested-by: David Hildenbrand <> Acked-by: Michal Hocko <> Cc: Dan Williams <> Cc: David Rientjes <> Cc: Ingo Molnar <> Cc: Ira Weiny <> Cc: James Morris <> Cc: Jason Gunthorpe <> Cc: Jason Gunthorpe <> Cc: John Hubbard <> Cc: Joonsoo Kim <> Cc: Matthew Wilcox <> Cc: Mel Gorman <> Cc: Michal Hocko <> Cc: Mike Kravetz <> Cc: Oscar Salvador <> Cc: Peter Zijlstra <> Cc: Sasha Levin <> Cc: Steven Rostedt (VMware) <> Cc: Tyler Hicks <> Cc: Vlastimil Babka <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'Documentation/admin-guide')
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst
index 5307f90738aa..05d51d2d8beb 100644
--- a/Documentation/admin-guide/mm/memory-hotplug.rst
+++ b/Documentation/admin-guide/mm/memory-hotplug.rst
@@ -357,6 +357,15 @@ creates ZONE_MOVABLE as following.
Unfortunately, there is no information to show which memory block belongs
+.. note::
+ Techniques that rely on long-term pinnings of memory (especially, RDMA and
+ vfio) are fundamentally problematic with ZONE_MOVABLE and, therefore, memory
+ hot remove. Pinned pages cannot reside on ZONE_MOVABLE, to guarantee that
+ memory can still get hot removed - be aware that pinning can fail even if
+ there is plenty of free memory in ZONE_MOVABLE. In addition, using
+ ZONE_MOVABLE might make page pinning more expensive, because pages have to be
+ migrated off that zone first.
.. _memory_hotplug_how_to_offline_memory:
How to offline memory