Re: [PATCH v2 00/12] memory-hotplug: hot-remove physical memory

From: Ni zhan Chen
Date: Tue Oct 23 2012 - 06:30:10 EST

On 10/23/2012 06:30 PM, wency@xxxxxxxxxxxxxx wrote:
From: Wen Congyang <wency@xxxxxxxxxxxxxx>

The patchset doesn't support kernel memory hot-remove, correct? If the answer is yes, you should point out in your patchset changelog.

The patch-set was divided from following thread's patch-set.

The last version of this patchset:

If you want to know the reason, please read following thread.

The patch-set has only the function of kernel core side for physical
memory hot remove. So if you use the patch, please apply following

- bug fix for memory hot remove
- acpi framework

The patches can free/remove the following things:

- /sys/firmware/memmap/X/{end, start, type} : [PATCH 2/10]
- mem_section and related sysfs files : [PATCH 3-4/10]
- memmap of sparse-vmemmap : [PATCH 5-7/10]
- page table of removed memory : [RFC PATCH 8/10]
- node and related sysfs files : [RFC PATCH 9-10/10]

* [PATCH 2/10] checks whether the memory can be removed or not.

If you find lack of function for physical memory hot-remove, please let me

How to test this patchset?
1. apply this patchset and build the kernel. MEMORY_HOTPLUG, MEMORY_HOTREMOVE,
ACPI_HOTPLUG_MEMORY must be selected.
2. load the module acpi_memhotplug
3. hotplug the memory device(it depends on your hardware)
You will see the memory device under the directory /sys/bus/acpi/devices/.
Its name is PNP0C80:XX.
4. online/offline pages provided by this memory device
You can write online/offline to /sys/devices/system/memory/memoryX/state to
online/offline pages provided by this memory device
5. hotremove the memory device
You can hotremove the memory device by the hardware, or writing 1 to

Note: if the memory provided by the memory device is used by the kernel, it
can't be offlined. It is not a bug.

Known problems:
1. hotremoving memory device may cause kernel panicked
This bug will be fixed by Liu Jiang's patch:

Changelogs from v1 to v2:
Patch1: new patch, offline memory twice. 1st iterate: offline every non primary
memory block. 2nd iterate: offline primary (i.e. first added) memory

Patch3: new patch, no logical change, just remove reduntant codes.

Patch9: merge the patch from wujianguo into this patch. flush tlb on all cpu
after the pagetable is changed.

Patch12: new patch, free node_data when a node is offlined

Wen Congyang (6):
memory-hotplug: try to offline the memory twice to avoid dependence
memory-hotplug: remove redundant codes
memory-hotplug: introduce new function arch_remove_memory() for
removing page table depends on architecture
memory-hotplug: remove page table of x86_64 architecture
memory-hotplug: remove sysfs file of node
memory-hotplug: free node_data when a node is offlined

Yasuaki Ishimatsu (6):
memory-hotplug: check whether all memory blocks are offlined or not
when removing memory
memory-hotplug: remove /sys/firmware/memmap/X sysfs
memory-hotplug: unregister memory section on SPARSEMEM_VMEMMAP
memory-hotplug: implement register_page_bootmem_info_section of
memory-hotplug: remove memmap of sparse-vmemmap
memory-hotplug: memory_hotplug: clear zone when removing the memory

arch/ia64/mm/discontig.c | 14 ++
arch/ia64/mm/init.c | 18 ++
arch/powerpc/mm/init_64.c | 14 ++
arch/powerpc/mm/mem.c | 12 +
arch/s390/mm/init.c | 12 +
arch/s390/mm/vmem.c | 14 ++
arch/sh/mm/init.c | 17 ++
arch/sparc/mm/init_64.c | 14 ++
arch/tile/mm/init.c | 8 +
arch/x86/include/asm/pgtable_types.h | 1 +
arch/x86/mm/init_32.c | 12 +
arch/x86/mm/init_64.c | 409 ++++++++++++++++++++++++++++++++++
arch/x86/mm/pageattr.c | 47 ++--
drivers/acpi/acpi_memhotplug.c | 8 +-
drivers/base/memory.c | 6 +
drivers/firmware/memmap.c | 98 ++++++++-
include/linux/firmware-map.h | 6 +
include/linux/memory_hotplug.h | 15 +-
include/linux/mm.h | 5 +-
mm/memory_hotplug.c | 409 ++++++++++++++++++++++++++++++++--
mm/sparse.c | 5 +-
21 files changed, 1087 insertions(+), 57 deletions(-)

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