Messages in this thread | | | Subject | Re: [PATCH v2 00/10] Copy Offload in NVMe Fabrics with P2P PCI Memory | From | Benjamin Herrenschmidt <> | Date | Fri, 02 Mar 2018 10:26:07 +1100 |
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On Thu, 2018-03-01 at 16:19 -0700, Logan Gunthorpe wrote:
(Switching back to my non-IBM address ...)
> 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
The big problem is not the vmemmap, it's the linear mapping.
Cheers, Ben.
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