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    SubjectRe: [7/8,v3] NUMA Hotplug Emulator: extend memory probe interface to support NUMA
    On Wed, Nov 17, 2010 at 01:18:50PM -0800, David Rientjes wrote:
    > On Wed, 17 Nov 2010, Dave Hansen wrote:
    > > The other thing that Greg suggested was to use configfs. Looking back
    > > on it, that makes a lot of sense. We can do better than these "probe"
    > > files.
    > >
    > > In your case, it might be useful to tell the kernel to be able to add
    > > memory in a node and add the node all in one go. That'll probably be
    > > closer to what the hardware will do, and will exercise different code
    > > paths that the separate "add node", "then add memory" steps that you're
    > > using here.
    > >
    > That seems like a seperate issue of moving the memory hotplug interface
    > over to configfs and that seems like it will cause a lot of userspace
    > breakage. The memory hotplug interface can already add memory to a node
    > without using the ACPI notifier, so what does it have to do with this
    > patchset?

    Agree with you, I do not suggest to implement it in this patchset.

    > I think what this patchset really wants to do is map offline hot-added
    > memory to a different node id before it is onlined. It needs no
    > additional command-line interface or kconfig options, users just need to
    > physically hot-add memory at runtime or use mem= when booting to reserve
    > present memory from being used.

    I already send out the implementation in another email, you can help to do
    a review.

    > Then, export the amount of memory that is actually physically present in
    > the e820 but was truncated by mem= and allow users to hot-add the memory
    > via the probe interface. Add a writeable 'node' file to offlined memory
    > section directories and allow it to be changed prior to online.

    for memory offlining, it is a known diffcult thing, and it is not supported
    well in current kernel, so I do not suggest to provide the offline interface
    in the emulator, it just take more pains. We can consider to add it when
    the memory offlining works well.

    Thanks & Regards,

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