Re: [rfc 08/45] cpu alloc: x86 support

[Christoph Lameter]

But one can subtract too... Hmmm... So the cpu area 0 could be put at
the beginning of the 2GB kernel area and then grow downwards from 
0xffffffff80000000. The cost in terms of code is one subtract
instruction for each per_cpu() or CPU_PTR()

The next thing doward from 0xffffffff80000000 is the vmemmap at 
0xffffe20000000000, so ~32TB. If we leave 16TB for the vmemmap
(a 16TB vmmemmap be able to map 2^(44 - 6 + 12) = 2^50 bytes 
more than currently supported by the processors)

then the remaining 16TB could be used to map 1GB per cpu for a 16k config. 
That is wildly overdoing it. Guess we could just do it with 1M anyways. 
Just to be safe we could do 128M. 128M x 16k = 2TB?

Would such a configuration be okay?

 

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