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Documentation: sysfs/memory: clarify some memory block device properties 

In commit 53cdc1cb29 ("drivers/base/memory.c: indicate all memory blocks
as removable") we changed the output of the "removable" property of memory
devices to return "1" if and only if the kernel supports memory offlining.

Let's update documentation, stating that the interface is legacy.  Also
update documentation of the "state" property and "valid_zones" properties.

Link: https://lkml.kernel.org/r/20210201181347.13262-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
master
David Hildenbrand 2021-02-25 17:17:28 -08:00 committed by Linus Torvalds
parent e9a2e48e87
commit a89107c047
2 changed files with 40 additions and 27 deletions
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51
Documentation/ABI/testing/sysfs-devices-memory
View File

@ -13,13 +13,13 @@ What: /sys/devices/system/memory/memoryX/removable
Date: June 2008
Contact: Badari Pulavarty <pbadari@us.ibm.com>
Description:
The file /sys/devices/system/memory/memoryX/removable
indicates whether this memory block is removable or not.
This is useful for a user-level agent to determine
identify removable sections of the memory before attempting
potentially expensive hot-remove memory operation
The file /sys/devices/system/memory/memoryX/removable is a
legacy interface used to indicated whether a memory block is
likely to be offlineable or not. Newer kernel versions return
"1" if and only if the kernel supports memory offlining.
Users: hotplug memory remove tools
http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils
lsmem/chmem part of util-linux
What: /sys/devices/system/memory/memoryX/phys_device
Date: September 2008
@ -44,23 +44,25 @@ Date: September 2008
Contact: Badari Pulavarty <pbadari@us.ibm.com>
Description:
The file /sys/devices/system/memory/memoryX/state
is read-write. When read, its contents show the
online/offline state of the memory section. When written,
root can toggle the the online/offline state of a removable
memory section (see removable file description above)
using the following commands::
is read-write. When read, it returns the online/offline
state of the memory block. When written, root can toggle
the online/offline state of a memory block using the following
commands::
# echo online > /sys/devices/system/memory/memoryX/state
# echo offline > /sys/devices/system/memory/memoryX/state
For example, if /sys/devices/system/memory/memory22/removable
contains a value of 1 and
/sys/devices/system/memory/memory22/state contains the
string "online" the following command can be executed by
by root to offline that section::
# echo offline > /sys/devices/system/memory/memory22/state
On newer kernel versions, advanced states can be specified
when onlining to select a target zone: "online_movable"
selects the movable zone. "online_kernel" selects the
applicable kernel zone (DMA, DMA32, or Normal). However,
after successfully setting one of the advanced states,
reading the file will return "online"; the zone information
can be obtained via "valid_zones" instead.
While onlining is unlikely to fail, there are no guarantees
that offlining will succeed. Offlining is more likely to
succeed if "valid_zones" indicates "Movable".
Users: hotplug memory remove tools
http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils
@ -70,8 +72,19 @@ Date: July 2014
Contact: Zhang Zhen <zhenzhang.zhang@huawei.com>
Description:
The file /sys/devices/system/memory/memoryX/valid_zones is
read-only and is designed to show which zone this memory
block can be onlined to.
read-only.
For online memory blocks, it returns in which zone memory
provided by a memory block is managed. If multiple zones
apply (not applicable for hotplugged memory), "None" is returned
and the memory block cannot be offlined.
For offline memory blocks, it returns by which zone memory
provided by a memory block can be managed when onlining.
The first returned zone ("default") will be used when setting
the state of an offline memory block to "online". Only one of
the kernel zones (DMA, DMA32, Normal) is applicable for a single
memory block.
What: /sys/devices/system/memoryX/nodeY
Date: October 2009

16
Documentation/admin-guide/mm/memory-hotplug.rst
View File

@ -162,14 +162,14 @@ Under each memory block, you can see 5 files:
which will be performed on all sections in the block.
``phys_device`` read-only: legacy interface only ever used on s390x to
expose the covered storage increment.
``removable`` read-only: contains an integer value indicating
whether the memory block is removable or not
removable. A value of 1 indicates that the memory
block is removable and a value of 0 indicates that
it is not removable. A memory block is removable only if
every section in the block is removable.
``valid_zones`` read-only: designed to show which zones this memory block
can be onlined to.
``removable`` read-only: legacy interface that indicated whether a memory
block was likely to be offlineable or not. Newer kernel
versions return "1" if and only if the kernel supports
memory offlining.
``valid_zones`` read-only: designed to show by which zone memory provided by
a memory block is managed, and to show by which zone memory
provided by an offline memory block could be managed when
onlining.
The first column shows it`s default zone.