[Vm-dev] Re: Cog Rump Xen unikernel (spur mmap)

[Ryan Macnak]

On Wed, Dec 16, 2015 at 3:20 PM, Ben Coman <btc at openinworld.com> wrote:

>
> On Thu, Dec 17, 2015 at 4:13 AM, Eliot Miranda <eliot.miranda at gmail.com>
> wrote:
> >
> > There are constraints here.  The VM assumes the following memory order:
> >
> > Low addresses:
> >     machine code zone
> >     new space
> >     first heap segment
> >
> > High addresses
> >     subsequent heap segments


I know new space < old space is relied on for store buffer checks. Is the
relative order of the code zone and the heap ever used?

Thinking long term, this reliance on ordering is bad for address space
randomization or having multiple heaps in the same process (e.g., having
concurrent actors with fast messaging). The Dart VM uses object alignment
to distinguish object age, though it doesn't have immediate characters or
floats contending for that bit.
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