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    SubjectRe: [PATCH part5 0/7] Arrange hotpluggable memory as ZONE_MOVABLE.
    Hey,

    On Tue, Aug 13, 2013 at 01:01:09AM +0800, Tang Chen wrote:
    > Sorry for the misunderstanding.
    >
    > I was trying to answer your question: "Why can't the kenrel allocate
    > hotpluggable memory opportunistic ?".

    I've used the wrong word, I was meaning best-effort, which is the only
    thing we can do anyway given that we have no control over where the
    kernel image is linked in relation to NUMA nodes.

    > If the kernel has any opportunity to allocate hotpluggable memory in
    > SRAT, then the kernel should tell users which memory is hotpluggable.
    >
    > But in what way ? I think node is the best for now. But a node could
    > have a lot of memory. If the kernel uses only a little memory, we will
    > lose the whole movable node, which I don't want to do.
    >
    > So, I don't want to allow the kenrel allocating hotpluggable memory
    > opportunistic.

    What I was saying was that the kernel should try !hotpluggable memory
    first then fall back to hotpluggable memory instead of failing boot as
    nothing really is worse than failing to boot.

    > >Short of being able to remap memory under the kernel, I don't think
    > >this can be very generic and as a compromise trying to keep as many
    > >hotpluggable nodes as possible doesn't sound too bad.
    >
    > I think making one of the node hotpluggable is better. But OK, it is
    > no big deal. There won't be such machine in reality, I think. :)

    Hmmm... but allocating close to kernel image will keep the number of
    nodes which are made un-removeable via permanent allocation to
    minimum. In most configurations that I can recall, I don't think we'd
    lose anything really and the code will be much simpler and generic.
    It seems like a good trade-off to me given that we need to report
    which nodes are hot unpluggable no matter what.

    Thanks.

    --
    tejun


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