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-rw-r--r--Documentation/ABI/testing/sysfs-devices-memory53
1 files changed, 33 insertions, 20 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-memory b/Documentation/ABI/testing/sysfs-devices-memory
index 58dbc592bc57..d8b0f80b9e33 100644
--- a/Documentation/ABI/testing/sysfs-devices-memory
+++ b/Documentation/ABI/testing/sysfs-devices-memory
@@ -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