[MLton] MLton rules! (was: filedes = int)
Sat, 16 Jul 2005 22:06:37 -0400
On Sat, 2005-07-16 at 12:51 -0700, Stephen Weeks wrote:
> > I think that you REALLY want to have the full 64-bits of address
> > space. =20
> We will certainly give that option.
> > If you don't, you might run into other problems like: where shared
> > libraries live in the address space; where files get mapped in
> > (which, after all, could be huge and also spread out so that they
> > can grow); etc.
> I don't see why it would be so hard for the OS to find us a contiguous
> 16GB somewhere. After all, it does have 64 bits of address space.
Actually, current x86-64 implementations only give you 48-bit virtual
addressing, but still use 64-bit pointers. (High bits of pointers must
be cleared, or the processor generates a fault.) So you don't get all of
64-bits of address space (on current processors), but 256TiB (48 bit) is
still pretty good.
See section 2.2.2 "64-bit Canonical Addresses" on page 18, which talks
of implementations supporting "fewer bits" of addresses:
And see the current Athlon 64 datasheet for that processor's address
size (40-bit physical, 48-bit virtual):
I know Intel processors currently have the same 48-bit virtual limit,
see section 220.127.116.11 "Canonical Addressing", page 3-12:
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