Hi Tang,
On Wed, 2013-01-09 at 17:32 +0800, Tang Chen wrote:
> Here is the physical memory hot-remove patch-set based on 3.8rc-2.
Some questions ask you, not has relationship with this patchset, but is
memory hotplug stuff.
1. In function node_states_check_changes_online:
comments:
* If we don't have HIGHMEM nor movable node,
* node_states[N_NORMAL_MEMORY] contains nodes which have zones of
* 0...ZONE_MOVABLE, set zone_last to ZONE_MOVABLE.
How to understand it? Why we don't have HIGHMEM nor movable node and
node_staes[N_NORMAL_MEMORY] contains 0...ZONE_MOVABLE, IIUC,
N_NORMAL_MEMORY only means the node has regular memory.
* If we don't have movable node, node_states[N_NORMAL_MEMORY]
* contains nodes which have zones of 0...ZONE_MOVABLE,
* set zone_last to ZONE_MOVABLE.
How to understand?
2. In function move_pfn_range_left, why end <= z2->zone_start_pfn is not
correct? The comments said that must include/overlap, why?
3. In function online_pages, the normal case(w/o online_kenrel,
online_movable), why not check if the new zone is overlap with adjacent
zones?
4. Could you summarize the difference implementation between hot-add and
logic-add, hot-remove and logic-remove?
>
> This patch-set aims to implement physical memory hot-removing.
>
> The patches can free/remove the following things:
>
> - /sys/firmware/memmap/X/{end, start, type} : [PATCH 4/15]
> - memmap of sparse-vmemmap : [PATCH 6,7,8,10/15]
> - page table of removed memory : [RFC PATCH 7,8,10/15]
> - node and related sysfs files : [RFC PATCH 13-15/15]
>
>
> Existing problem:
> If CONFIG_MEMCG is selected, we will allocate memory to store page cgroup
> when we online pages.
>
> 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, 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 patch1, we provide a solution which is not good enough:
> Iterate twice to offline the memory.
> 1st iterate: offline every non primary memory block.
> 2nd iterate: offline primary (i.e. first added) memory block.
>
> And a new idea from Wen Congyang <wency@xxxxxxxxxxxxxx> is:
> allocate the memory from the memory block they are describing.
>
> But we are not sure if it is OK to do so because there is not existing API
> to do so, and we need to move page_cgroup memory allocation from MEM_GOING_ONLINE
> to MEM_ONLINE. And also, it may interfere the hugepage.
>
>
>
> 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
> /sys/bus/acpi/devices/PNP0C80:XX/eject.
Is there a similar knode to hot-add the memory device?
>
>
> Note: if the memory provided by the memory device is used by the kernel, it
> can't be offlined. It is not a bug.
>
>
> Changelogs from v5 to v6:
> Patch3: Add some more comments to explain memory hot-remove.
> Patch4: Remove bootmem member in struct firmware_map_entry.
> Patch6: Repeatedly register bootmem pages when using hugepage.
> Patch8: Repeatedly free bootmem pages when using hugepage.
> Patch14: Don't free pgdat when offlining a node, just reset it to 0.
> Patch15: New patch, pgdat is not freed in patch14, so don't allocate a new
> one when online a node.
>
> Changelogs from v4 to v5:
> Patch7: new patch, move pgdat_resize_lock into sparse_remove_one_section() to
> avoid disabling irq because we need flush tlb when free pagetables.
> Patch8: new patch, pick up some common APIs that are used to free direct mapping
> and vmemmap pagetables.
> Patch9: free direct mapping pagetables on x86_64 arch.
> Patch10: free vmemmap pagetables.
> Patch11: since freeing memmap with vmemmap has been implemented, the config
> macro CONFIG_SPARSEMEM_VMEMMAP when defining __remove_section() is
> no longer needed.
> Patch13: no need to modify acpi_memory_disable_device() since it was removed,
> and add nid parameter when calling remove_memory().
>
> Changelogs from v3 to v4:
> Patch7: remove unused codes.
> Patch8: fix nr_pages that is passed to free_map_bootmem()
>
> Changelogs from v2 to v3:
> Patch9: call sync_global_pgds() if pgd is changed
> Patch10: fix a problem int the 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
> block.
>
> 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.
>
>
> Tang Chen (6):
> memory-hotplug: move pgdat_resize_lock into
> sparse_remove_one_section()
> memory-hotplug: remove page table of x86_64 architecture
> memory-hotplug: remove memmap of sparse-vmemmap
> memory-hotplug: Integrated __remove_section() of
> CONFIG_SPARSEMEM_VMEMMAP.
> memory-hotplug: remove sysfs file of node
> memory-hotplug: Do not allocate pdgat if it was not freed when
> offline.
>
> Wen Congyang (5):
> 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: Common APIs to support page tables hot-remove
> memory-hotplug: free node_data when a node is offlined
>
> Yasuaki Ishimatsu (4):
> memory-hotplug: check whether all memory blocks are offlined or not
> when removing memory
> memory-hotplug: remove /sys/firmware/memmap/X sysfs
> memory-hotplug: implement register_page_bootmem_info_section of
> sparse-vmemmap
> memory-hotplug: memory_hotplug: clear zone when removing the memory
>
> arch/arm64/mm/mmu.c | 3 +
> arch/ia64/mm/discontig.c | 10 +
> arch/ia64/mm/init.c | 18 ++
> arch/powerpc/mm/init_64.c | 10 +
> arch/powerpc/mm/mem.c | 12 +
> arch/s390/mm/init.c | 12 +
> arch/s390/mm/vmem.c | 10 +
> arch/sh/mm/init.c | 17 ++
> arch/sparc/mm/init_64.c | 10 +
> 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 | 390 +++++++++++++++++++++++++++++
> arch/x86/mm/pageattr.c | 47 ++--
> drivers/acpi/acpi_memhotplug.c | 8 +-
> drivers/base/memory.c | 6 +
> drivers/firmware/memmap.c | 96 +++++++-
> include/linux/bootmem.h | 1 +
> include/linux/firmware-map.h | 6 +
> include/linux/memory_hotplug.h | 15 +-
> include/linux/mm.h | 4 +-
> mm/memory_hotplug.c | 459 +++++++++++++++++++++++++++++++---
> mm/sparse.c | 8 +-
> 23 files changed, 1094 insertions(+), 69 deletions(-)
>
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