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c04fc586c1
Show node to memory section relationship with symlinks in sysfs
Add /sys/devices/system/node/nodeX/memoryY symlinks for all
the memory sections located on nodeX. For example:
/sys/devices/system/node/node1/memory135 -> ../../memory/memory135
indicates that memory section 135 resides on node1.
Also revises documentation to cover this change as well as updating
Documentation/ABI/testing/sysfs-devices-memory to include descriptions
of memory hotremove files 'phys_device', 'phys_index', and 'state'
that were previously not described there.
In addition to it always being a good policy to provide users with
the maximum possible amount of physical location information for
resources that can be hot-added and/or hot-removed, the following
are some (but likely not all) of the user benefits provided by
this change.
Immediate:
- Provides information needed to determine the specific node
on which a defective DIMM is located. This will reduce system
downtime when the node or defective DIMM is swapped out.
- Prevents unintended onlining of a memory section that was
previously offlined due to a defective DIMM. This could happen
during node hot-add when the user or node hot-add assist script
onlines _all_ offlined sections due to user or script inability
to identify the specific memory sections located on the hot-added
node. The consequences of reintroducing the defective memory
could be ugly.
- Provides information needed to vary the amount and distribution
of memory on specific nodes for testing or debugging purposes.
Future:
- Will provide information needed to identify the memory
sections that need to be offlined prior to physical removal
of a specific node.
Symlink creation during boot was tested on 2-node x86_64, 2-node
ppc64, and 2-node ia64 systems. Symlink creation during physical
memory hot-add tested on a 2-node x86_64 system.
Signed-off-by: Gary Hade <garyhade@us.ibm.com>
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
73 lines
2.9 KiB
Text
73 lines
2.9 KiB
Text
What: /sys/devices/system/memory
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Date: June 2008
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Contact: Badari Pulavarty <pbadari@us.ibm.com>
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Description:
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The /sys/devices/system/memory contains a snapshot of the
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internal state of the kernel memory blocks. Files could be
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added or removed dynamically to represent hot-add/remove
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operations.
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Users: hotplug memory add/remove tools
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https://w3.opensource.ibm.com/projects/powerpc-utils/
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What: /sys/devices/system/memory/memoryX/removable
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Date: June 2008
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Contact: Badari Pulavarty <pbadari@us.ibm.com>
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Description:
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The file /sys/devices/system/memory/memoryX/removable
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indicates whether this memory block is removable or not.
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This is useful for a user-level agent to determine
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identify removable sections of the memory before attempting
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potentially expensive hot-remove memory operation
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Users: hotplug memory remove tools
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https://w3.opensource.ibm.com/projects/powerpc-utils/
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What: /sys/devices/system/memory/memoryX/phys_device
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Date: September 2008
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Contact: Badari Pulavarty <pbadari@us.ibm.com>
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Description:
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The file /sys/devices/system/memory/memoryX/phys_device
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is read-only and is designed to show the name of physical
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memory device. Implementation is currently incomplete.
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What: /sys/devices/system/memory/memoryX/phys_index
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Date: September 2008
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Contact: Badari Pulavarty <pbadari@us.ibm.com>
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Description:
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The file /sys/devices/system/memory/memoryX/phys_index
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is read-only and contains the section ID in hexadecimal
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which is equivalent to decimal X contained in the
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memory section directory name.
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What: /sys/devices/system/memory/memoryX/state
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Date: September 2008
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Contact: Badari Pulavarty <pbadari@us.ibm.com>
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Description:
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The file /sys/devices/system/memory/memoryX/state
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is read-write. When read, it's contents show the
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online/offline state of the memory section. When written,
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root can toggle the the online/offline state of a removable
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memory section (see removable file description above)
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using the following commands.
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# echo online > /sys/devices/system/memory/memoryX/state
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# echo offline > /sys/devices/system/memory/memoryX/state
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For example, if /sys/devices/system/memory/memory22/removable
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contains a value of 1 and
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/sys/devices/system/memory/memory22/state contains the
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string "online" the following command can be executed by
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by root to offline that section.
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# echo offline > /sys/devices/system/memory/memory22/state
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Users: hotplug memory remove tools
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https://w3.opensource.ibm.com/projects/powerpc-utils/
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What: /sys/devices/system/node/nodeX/memoryY
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Date: September 2008
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Contact: Gary Hade <garyhade@us.ibm.com>
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Description:
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When CONFIG_NUMA is enabled
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/sys/devices/system/node/nodeX/memoryY is a symbolic link that
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points to the corresponding /sys/devices/system/memory/memoryY
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memory section directory. For example, the following symbolic
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link is created for memory section 9 on node0.
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/sys/devices/system/node/node0/memory9 -> ../../memory/memory9
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