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    SubjectRe: [PATCH v2 00/10] Copy Offload in NVMe Fabrics with P2P PCI Memory


    On 01/03/18 04:00 PM, Benjamin Herrenschmidt wrote:
    > We use only 52 in practice but yes.
    >
    >> That's 64PB. If you use need
    >> a sparse vmemmap for the entire space it will take 16TB which leaves you
    >> with 63.98PB of address space left. (Similar calculations for other
    >> numbers of address bits.)
    >
    > We only have 52 bits of virtual space for the kernel with the radix
    > MMU.

    Ok, assuming you only have 52 bits of physical address space: the sparse
    vmemmap takes 1TB and you're left with 3.9PB of address space for other
    things. So, again, why doesn't that work? Is my math wrong?

    Logan

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