Subject: Re: [RFC v9 PATCH 00/21] memory-hotplug: hot-remove physical memory

From: Yasuaki Ishimatsu <[email-masked]>
Date: Mon, 1 Oct 2012 13:44:42 +0900

Hi Chen,

2012/09/29 17:19, Ni zhan Chen wrote:
> On 09/05/2012 05:25 PM, [email-masked] wrote:
>> From: Wen Congyang <[email-masked]>
>>
>> This patch series aims to support physical memory hot-remove.
>>
>> The patches can free/remove the following things:
>>
>>    - acpi_memory_info                          : [RFC PATCH 4/19]
>>    - /sys/firmware/memmap/X/{end, start, type} : [RFC PATCH 8/19]
>>    - iomem_resource                            : [RFC PATCH 9/19]
>>    - mem_section and related sysfs files       : [RFC PATCH 10-11, 13-16/19]
>>    - page table of removed memory              : [RFC PATCH 12/19]
>>    - node and related sysfs files              : [RFC PATCH 18-19/19]
>>
>> If you find lack of function for physical memory hot-remove, please let me
>> know.
>>
>> 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
>
> Hi Yasuaki,
>
> where is the acpi_memhotplug module?

If you build acpi_memhotplug as module, it is created under
/lib/modules/<kernel-version>/driver/acpi/ directory. It depends
on config ACPI_HOTPLUG_MEMORY. The confing is [*], it becomes built-in
function. So you don't need to care about it.  

Thanks,
Yasuaki Ishimatsu

>
>> 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
>>     /sys/bus/acpi/devices/PNP0C80:XX/eject.
>>
>> 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. memory can't be offlined when CONFIG_MEMCG is selected.
>>     For example: there is a memory device on node 1. The address range
>>     is [1G, 1.5G). You will find 4 new directories memory8, memory9, memory10,
>>     and memory11 under the directory /sys/devices/system/memory/.
>>     If CONFIG_MEMCG is selected, we will allocate memory to store page cgroup
>>     when we online pages. When we online memory8, the memory stored page cgroup
>>     is not provided by this memory device. But when we online memory9, the memory
>>     stored page cgroup may be provided by memory8. So we can't offline memory8
>>     now. We should offline the memory in the reversed order.
>>     When the memory device is hotremoved, we will auto offline memory provided
>>     by this memory device. But we don't know which memory is onlined first, so
>>     offlining memory may fail. In such case, you should offline the memory by
>>     hand before hotremoving the memory device.
>> 2. hotremoving memory device may cause kernel panicked
>>     This bug will be fixed by Liu Jiang's patch:
>>     https://lkml.org/lkml/2012/7/3/1
>>
>> change log of v9:
>>   [RFC PATCH v9 8/21]
>>     * add a lock to protect the list map_entries
>>     * add an indicator to firmware_map_entry to remember whether the memory
>>       is allocated from bootmem
>>   [RFC PATCH v9 10/21]
>>     * change the macro to inline function
>>   [RFC PATCH v9 19/21]
>>     * don't offline the node if the cpu on the node is onlined
>>   [RFC PATCH v9 21/21]
>>     * create new patch: auto offline page_cgroup when onlining memory block
>>       failed
>>
>> change log of v8:
>>   [RFC PATCH v8 17/20]
>>     * Fix problems when one node's range include the other nodes
>>   [RFC PATCH v8 18/20]
>>     * fix building error when CONFIG_MEMORY_HOTPLUG_SPARSE or CONFIG_HUGETLBFS
>>       is not defined.
>>   [RFC PATCH v8 19/20]
>>     * don't offline node when some memory sections are not removed
>>   [RFC PATCH v8 20/20]
>>     * create new patch: clear hwpoisoned flag when onlining pages
>>
>> change log of v7:
>>   [RFC PATCH v7 4/19]
>>     * do not continue if acpi_memory_device_remove_memory() fails.
>>   [RFC PATCH v7 15/19]
>>     * handle usemap in register_page_bootmem_info_section() too.
>>
>> change log of v6:
>>   [RFC PATCH v6 12/19]
>>     * fix building error on other archtitectures than x86
>>
>>   [RFC PATCH v6 15-16/19]
>>     * fix building error on other archtitectures than x86
>>
>> change log of v5:
>>   * merge the patchset to clear page table and the patchset to hot remove
>>     memory(from ishimatsu) to one big patchset.
>>
>>   [RFC PATCH v5 1/19]
>>     * rename remove_memory() to offline_memory()/offline_pages()
>>
>>   [RFC PATCH v5 2/19]
>>     * new patch: implement offline_memory(). This function offlines pages,
>>       update memory block's state, and notify the userspace that the memory
>>       block's state is changed.
>>
>>   [RFC PATCH v5 4/19]
>>     * offline and remove memory in acpi_memory_disable_device() too.
>>
>>   [RFC PATCH v5 17/19]
>>     * new patch: add a new function __remove_zone() to revert the things done
>>       in the function __add_zone().
>>
>>   [RFC PATCH v5 18/19]
>>     * flush work befor reseting node device.
>>
>> change log of v4:
>>   * remove "memory-hotplug : unify argument of firmware_map_add_early/hotplug"
>>     from the patch series, since the patch is a bugfix. It is being disccussed
>>     on other thread. But for testing the patch series, the patch is needed.
>>     So I added the patch as [PATCH 0/13].
>>
>>   [RFC PATCH v4 2/13]
>>     * check memory is online or not at remove_memory()
>>     * add memory_add_physaddr_to_nid() to acpi_memory_device_remove() for
>>       getting node id
>>   [RFC PATCH v4 3/13]
>>     * create new patch : check memory is online or not at online_pages()
>>
>>   [RFC PATCH v4 4/13]
>>     * add __ref section to remove_memory()
>>     * call firmware_map_remove_entry() before remove_sysfs_fw_map_entry()
>>
>>   [RFC PATCH v4 11/13]
>>     * rewrite register_page_bootmem_memmap() for removing page used as PT/PMD
>>
>> change log of v3:
>>   * rebase to 3.5.0-rc6
>>
>>   [RFC PATCH v2 2/13]
>>     * remove extra kobject_put()
>>
>>     * The patch was commented by Wen. Wen's comment is
>>       "acpi_memory_device_remove() should ignore a return value of
>>       remove_memory() since caller does not care the return value".
>>       But I did not change it since I think caller should care the
>>       return value. And I am trying to fix it as follow:
>>
>>       https://lkml.org/lkml/2012/7/5/624
>>
>>   [RFC PATCH v2 4/13]
>>     * remove a firmware_memmap_entry allocated by kzmalloc()
>>
>> change log of v2:
>>   [RFC PATCH v2 2/13]
>>     * check whether memory block is offline or not before calling offline_memory()
>>     * check whether section is valid or not in is_memblk_offline()
>>     * call kobject_put() for each memory_block in is_memblk_offline()
>>
>>   [RFC PATCH v2 3/13]
>>     * unify the end argument of firmware_map_add_early/hotplug
>>
>>   [RFC PATCH v2 4/13]
>>     * add release_firmware_map_entry() for freeing firmware_map_entry
>>
>>   [RFC PATCH v2 6/13]
>>    * add release_memory_block() for freeing memory_block
>>
>>   [RFC PATCH v2 11/13]
>>    * fix wrong arguments of free_pages()
>>
>>
>> Wen Congyang (8):
>>    memory-hotplug: implement offline_memory()
>>    memory-hotplug: store the node id in acpi_memory_device
>>    memory-hotplug: export the function acpi_bus_remove()
>>    memory-hotplug: call acpi_bus_remove() to remove memory device
>>    memory-hotplug: introduce new function arch_remove_memory()
>>    memory-hotplug: remove sysfs file of node
>>    memory-hotplug: clear hwpoisoned flag when onlining pages
>>    memory-hotplug: auto offline page_cgroup when onlining memory block
>>      failed
>>
>> Yasuaki Ishimatsu (13):
>>    memory-hotplug: rename remove_memory() to
>>      offline_memory()/offline_pages()
>>    memory-hotplug: offline and remove memory when removing the memory
>>      device
>>    memory-hotplug: check whether memory is present or not
>>    memory-hotplug: remove /sys/firmware/memmap/X sysfs
>>    memory-hotplug: does not release memory region in PAGES_PER_SECTION
>>      chunks
>>    memory-hotplug: add memory_block_release
>>    memory-hotplug: remove_memory calls __remove_pages
>>    memory-hotplug: check page type in get_page_bootmem
>>    memory-hotplug: move register_page_bootmem_info_node and
>>      put_page_bootmem for sparse-vmemmap
>>    memory-hotplug: implement register_page_bootmem_info_section of
>>      sparse-vmemmap
>>    memory-hotplug: free memmap of sparse-vmemmap
>>    memory_hotplug: clear zone when the memory is removed
>>    memory-hotplug: add node_device_release
>>
>>   arch/ia64/mm/discontig.c                        |   14 +
>>   arch/ia64/mm/init.c                             |   16 +
>>   arch/powerpc/mm/init_64.c                       |   14 +
>>   arch/powerpc/mm/mem.c                           |   14 +
>>   arch/powerpc/platforms/pseries/hotplug-memory.c |   16 +-
>>   arch/s390/mm/init.c                             |   12 +
>>   arch/s390/mm/vmem.c                             |   14 +
>>   arch/sh/mm/init.c                               |   15 +
>>   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                           |   10 +
>>   arch/x86/mm/init_64.c                           |  331 ++++++++++++++++++
>>   arch/x86/mm/pageattr.c                          |   47 ++--
>>   drivers/acpi/acpi_memhotplug.c                  |   54 +++-
>>   drivers/acpi/scan.c                             |    3 +-
>>   drivers/base/memory.c                           |   88 ++++-
>>   drivers/base/node.c                             |   11 +
>>   drivers/firmware/memmap.c                       |   98 +++++-
>>   include/acpi/acpi_bus.h                         |    1 +
>>   include/linux/firmware-map.h                    |    6 +
>>   include/linux/memory.h                          |    5 +
>>   include/linux/memory_hotplug.h                  |   25 +-
>>   include/linux/mm.h                              |    5 +-
>>   include/linux/mmzone.h                          |   19 +
>>   mm/memory_hotplug.c                             |  424 +++++++++++++++++++++--
>>   mm/page_cgroup.c                                |    3 +
>>   mm/sparse.c                                     |    5 +-
>>   28 files changed, 1181 insertions(+), 92 deletions(-)
>>
>> --
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>