On 08.06.21 15:38, David Hildenbrand wrote:
The memory hot(un)plug documentation is outdated and incomplete. Most of
the content dates back to 2007, so it's time for a major overhaul.
Let's rewrite, reorganize and update most parts of the documentation. In
addition to memory hot(un)plug, also add some details regarding
ZONE_MOVABLE, with memory hotunplug being one of its main consumers.
Drop the file history, that information can more reliably be had from
the git log.
The style of the document is also properly fixed that e.g., "restview"
renders it cleanly now.
In the future, we might add some more details about virt users like
virtio-mem, the XEN balloon, the Hyper-V balloon and ppc64 dlpar.
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: linux-doc@xxxxxxxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
After a follow-up discussion on v1, the following on top:
diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst
index 353b67e76439..15330ad4b764 100644
--- a/Documentation/admin-guide/mm/memory-hotplug.rst
+++ b/Documentation/admin-guide/mm/memory-hotplug.rst
@@ -35,7 +35,7 @@ used to expose persistent memory, other performance-differentiated memory and
reserved memory regions as ordinary system RAM to Linux.
Linux only supports memory hot(un)plug on selected 64 bit architectures, such as
-x86_64, aarch64, ppc64, s390x and ia64.
+x86_64, arm64, ppc64, s390x and ia64.
Memory Hot(Un)Plug Granularity
------------------------------
@@ -178,9 +178,9 @@ Or one can explicitly request a kernel zone (usually ZONE_NORMAL) by::
% echo online_kernel > /sys/devices/system/memory/memoryXXX/state
-In any case, if offline succeeds, the state of the memory block is changed to be
-"online". If it fails, an error will be returned by the kernel via the system
-call that triggered the respective file modification.
+In any case, if onlining succeeds, the state of the memory block is changed to
+be "online". If it fails, the state of the memory block will remain unchanged
+and the above commands will fail.
Onlining Memory Blocks Automatically
------------------------------------
@@ -234,8 +234,15 @@ Or alternatively::
% echo 0 > /sys/devices/system/memory/memoryXXX/online
-If offline succeeds, the state of the memory block is changed to be "offline".
-If it fails, an error will be returned by the kernel.
+If offlining succeeds, the state of the memory block is changed to be "offline".
+If it fails, the state of the memory block will remain unchanged and the above
+commands will fail, for example, via::
+
+ bash: echo: write error: Device or resource busy
+
+or via::
+
+ bash: echo: write error: Invalid argument
Observing the State of Memory Blocks
------------------------------------
@@ -535,7 +542,7 @@ block might fail:
offlining; this applies to memory blocks present during boot only.
- Special memory blocks prevented by the system from getting offlined. Examples
- include any memory available during boot on aarch64 or memory blocks spanning
+ include any memory available during boot on arm64 or memory blocks spanning
the crashkernel area on s390x; this usually applies to memory blocks present
during boot only.
--
Thanks,
David / dhildenb
