red seg size philosophy question

[Jonathan S. Shapiro]

> Just as a question, would it be reasonable to have a call in the vcsk 
> interface which basically states "Truncate (if necessary) to x
> bytes...

Truncating to X bytes is hard, but truncating to X pages is feasible.

> and do not extend the segment past x bytes"?

It might be useful to have a keeper that enforced this, but the
original VCSK as I understand it does not do so.  The truncate
operation causes all data past X to revert to zero (which are low
cost, because they are from the primordial zero segment.

> Which brings up another question in my mind:  Should there be a way
> to make pages in a vsck "not there", in the sense that accessing
> them will cause the domain keeper to be invoked.

Actually, accessing them would cause the segment keeper to be invoked.

Once again, you've identified potentially useful functionality.  Let's 
keep VCSK as simple as feasible and explore enhancements afterwards.