From: Pavel Tatashin <pasha.tatashin@soleen.com>
To: pasha.tatashin@soleen.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, akpm@linux-foundation.org, vbabka@suse.cz,
mhocko@suse.com, david@redhat.com, osalvador@suse.de,
dan.j.williams@intel.com, sashal@kernel.org,
tyhicks@linux.microsoft.com, iamjoonsoo.kim@lge.com,
mike.kravetz@oracle.com, rostedt@goodmis.org, mingo@redhat.com,
jgg@ziepe.ca, peterz@infradead.org, mgorman@suse.de,
willy@infradead.org, rientjes@google.com, jhubbard@nvidia.com,
linux-doc@vger.kernel.org
Subject: [PATCH v3 6/6] memory-hotplug.rst: add a note about ZONE_MOVABLE and page pinning
Date: Fri, 11 Dec 2020 15:21:40 -0500 [thread overview]
Message-ID: <20201211202140.396852-7-pasha.tatashin@soleen.com> (raw)
In-Reply-To: <20201211202140.396852-1-pasha.tatashin@soleen.com>
Document the special handling of page pinning when ZONE_MOVABLE present.
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Suggested-by: David Hildenbrand <david@redhat.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
prev parent reply other threads:[~2020-12-11 21:30 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-11 20:21 [PATCH v3 0/6] prohibit pinning pages in ZONE_MOVABLE Pavel Tatashin
2020-12-11 20:21 ` [PATCH v3 1/6] mm/gup: don't pin migrated cma pages in movable zone Pavel Tatashin
2020-12-11 20:21 ` [PATCH v3 2/6] mm cma: rename PF_MEMALLOC_NOCMA to PF_MEMALLOC_PIN Pavel Tatashin
2020-12-14 14:03 ` Michal Hocko
2020-12-15 4:37 ` Pavel Tatashin
2020-12-11 20:21 ` [PATCH v3 3/6] mm: apply per-task gfp constraints in fast path Pavel Tatashin
2020-12-14 14:09 ` Michal Hocko
2020-12-15 5:20 ` Pavel Tatashin
2020-12-15 8:25 ` Michal Hocko
2020-12-15 17:35 ` Pavel Tatashin
2020-12-11 20:21 ` [PATCH v3 4/6] mm: honor PF_MEMALLOC_PIN for all movable pages Pavel Tatashin
2020-12-14 14:17 ` Michal Hocko
2020-12-15 5:24 ` Pavel Tatashin
2020-12-15 8:27 ` Michal Hocko
2020-12-15 17:28 ` Pavel Tatashin
2020-12-11 20:21 ` [PATCH v3 5/6] mm/gup: migrate pinned pages out of movable zone Pavel Tatashin
2020-12-11 20:23 ` Jason Gunthorpe
2020-12-11 20:40 ` Pavel Tatashin
2020-12-11 20:46 ` Jason Gunthorpe
2020-12-11 21:09 ` Pavel Tatashin
2020-12-11 21:29 ` David Hildenbrand
2020-12-11 21:35 ` Pavel Tatashin
2020-12-11 21:53 ` David Hildenbrand
2020-12-11 23:00 ` Pavel Tatashin
2020-12-12 0:07 ` John Hubbard
2020-12-11 23:50 ` Jason Gunthorpe
2020-12-12 7:29 ` David Hildenbrand
2020-12-14 13:36 ` Jason Gunthorpe
2020-12-14 14:21 ` David Hildenbrand
2020-12-14 14:30 ` Michal Hocko
2020-12-14 14:19 ` Michal Hocko
2020-12-11 20:21 ` Pavel Tatashin [this message]
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