Re: XFS unhappy with large holey loopback and syncs -- [OT] vmalloc 45-bit/32PiB address limit

["Bryan J. Smith" <b.j.smith@xxxxxxxx>]

Andi Kleen <ak@xxxxxxx> wrote:
> x86-64 supports 48bits of address space. Half of it is for 
> user space, the other half for the kernel.  Of the kernel
> half half is for physical memory, and half of the other
> half is for kernel text and holes. This leaves 45bits for
> vmalloc.

Ahhh, that makes sense.

I knew x86-64 "Long Mode" is 48-bit (linear segment+offset
register/i486 TLB compatible, hence how it can run 32-bit
applications), but never stopped to think about the mapping
of kernel and user-space memory.

Thanx for explaining it!


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