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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 updates relevant kexec
segments on memory hot un/plug and/or on/offline events, avoiding the
need to reload kdump kernel.
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