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+What: /sys/devices/system/memory
+Date: June 2008
+Contact: Badari Pulavarty <pbadari@us.ibm.com>
+Description:
+ The /sys/devices/system/memory contains a snapshot of the
+ internal state of the kernel memory blocks. Files could be
+ added or removed dynamically to represent hot-add/remove
+ operations.
+Users: hotplug memory add/remove tools
+ http://www.ibm.com/developerworks/wikis/display/LinuxP/powerpc-utils
+
+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 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
+Contact: Badari Pulavarty <pbadari@us.ibm.com>
+Description:
+ The file /sys/devices/system/memory/memoryX/phys_device
+ is read-only; it is a legacy interface only ever used on s390x
+ to expose the covered storage increment.
+Users: Legacy s390-tools lsmem/chmem
+
+What: /sys/devices/system/memory/memoryX/phys_index
+Date: September 2008
+Contact: Badari Pulavarty <pbadari@us.ibm.com>
+Description:
+ The file /sys/devices/system/memory/memoryX/phys_index
+ is read-only and contains the section ID in hexadecimal
+ which is equivalent to decimal X contained in the
+ memory section directory name.
+
+What: /sys/devices/system/memory/memoryX/state
+Date: September 2008
+Contact: Badari Pulavarty <pbadari@us.ibm.com>
+Description:
+ The file /sys/devices/system/memory/memoryX/state
+ 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
+
+ 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
+
+
+What: /sys/devices/system/memory/memoryX/valid_zones
+Date: July 2014
+Contact: Zhang Zhen <zhenzhang.zhang@huawei.com>
+Description:
+ The file /sys/devices/system/memory/memoryX/valid_zones is
+ 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
+Contact: Linux Memory Management list <linux-mm@kvack.org>
+Description:
+ When CONFIG_NUMA is enabled, a symbolic link that
+ points to the corresponding NUMA node directory.
+
+ For example, the following symbolic link is created for
+ memory section 9 on node0:
+
+ /sys/devices/system/memory/memory9/node0 -> ../../node/node0
+
+
+What: /sys/devices/system/node/nodeX/memoryY
+Date: September 2008
+Contact: Gary Hade <garyhade@us.ibm.com>
+Description:
+ When CONFIG_NUMA is enabled
+ /sys/devices/system/node/nodeX/memoryY is a symbolic link that
+ points to the corresponding /sys/devices/system/memory/memoryY
+ memory section directory. For example, the following symbolic
+ link is created for memory section 9 on node0.
+
+ /sys/devices/system/node/node0/memory9 -> ../../memory/memory9
+
+What: /sys/devices/system/memory/crash_hotplug
+Date: Aug 2023
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+Description:
+ (RO) indicates whether or not the kernel directly supports
+ modifying the crash elfcorehdr for memory hot un/plug and/or
+ on/offline changes.