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r: 235465
b: refs/heads/master
c: 0c2c99b
h: refs/heads/master
i:
  235463: 120c4a2
v: v3
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Nathan Fontenot authored and Greg Kroah-Hartman committed Feb 4, 2011
1 parent f47f827 commit ee24aeb
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2 changes: 1 addition & 1 deletion [refs]
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refs/heads/master: e8d9792aa514e49bf618713987c393d93babc2c5
refs/heads/master: 0c2c99b1b8ab5d294f176d631e945ebdefcce4cd
47 changes: 31 additions & 16 deletions trunk/Documentation/memory-hotplug.txt
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Expand Up @@ -126,36 +126,51 @@ config options.
--------------------------------
4 sysfs files for memory hotplug
--------------------------------
All sections have their device information under /sys/devices/system/memory as
All sections have their device information in sysfs. Each section is part of
a memory block under /sys/devices/system/memory as

/sys/devices/system/memory/memoryXXX
(XXX is section id.)
(XXX is the section id.)

Now, XXX is defined as start_address_of_section / section_size.
Now, XXX is defined as (start_address_of_section / section_size) of the first
section contained in the memory block. The files 'phys_index' and
'end_phys_index' under each directory report the beginning and end section id's
for the memory block covered by the sysfs directory. It is expected that all
memory sections in this range are present and no memory holes exist in the
range. Currently there is no way to determine if there is a memory hole, but
the existence of one should not affect the hotplug capabilities of the memory
block.

For example, assume 1GiB section size. A device for a memory starting at
0x100000000 is /sys/device/system/memory/memory4
(0x100000000 / 1Gib = 4)
This device covers address range [0x100000000 ... 0x140000000)

Under each section, you can see 4 files.
Under each section, you can see 4 or 5 files, the end_phys_index file being
a recent addition and not present on older kernels.

/sys/devices/system/memory/memoryXXX/phys_index
/sys/devices/system/memory/memoryXXX/start_phys_index
/sys/devices/system/memory/memoryXXX/end_phys_index
/sys/devices/system/memory/memoryXXX/phys_device
/sys/devices/system/memory/memoryXXX/state
/sys/devices/system/memory/memoryXXX/removable

'phys_index' : read-only and contains section id, same as XXX.
'state' : read-write
at read: contains online/offline state of memory.
at write: user can specify "online", "offline" command
'phys_device': read-only: designed to show the name of physical memory device.
This is not well implemented now.
'removable' : read-only: contains an integer value indicating
whether the memory section is removable or not
removable. A value of 1 indicates that the memory
section is removable and a value of 0 indicates that
it is not removable.
'phys_index' : read-only and contains section id of the first section
in the memory block, same as XXX.
'end_phys_index' : read-only and contains section id of the last section
in the memory block.
'state' : read-write
at read: contains online/offline state of memory.
at write: user can specify "online", "offline" command
which will be performed on al sections in the block.
'phys_device' : read-only: designed to show the name of physical memory
device. This is not well implemented now.
'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.

NOTE:
These directories/files appear after physical memory hotplug phase.
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