On Thu 17-12-20 13:52:39, Pavel Tatashin wrote: > Document the special handling of page pinning when ZONE_MOVABLE present. > > Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> > Suggested-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> > --- > 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 > -- Michal Hocko SUSE Labs
