[PATCH v7 10/14] memory-hotplug.rst: add a note about ZONE_MOVABLE and page pinning
From: Pavel Tatashin <pasha.tatashin@soleen.com>
Date: 2021-01-22 03:41:02
Also in:
linux-kselftest, linux-mm, lkml
Subsystem:
documentation, memory hot(un)plug, memory management - misc, the rest · Maintainers:
Jonathan Corbet, David Hildenbrand, Oscar Salvador, Andrew Morton, Linus Torvalds
Document the special handling of page pinning when ZONE_MOVABLE present. Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com> Suggested-by: David Hildenbrand <redacted> Acked-by: Michal Hocko <mhocko@suse.com> --- Documentation/admin-guide/mm/memory-hotplug.rst | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst
index 5c4432c96c4b..c6618f99f765 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 to ZONE_MOVABLE. This is TBD. +.. 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
--
2.25.1