Re: Why *not* rmap, anyway?

["Martin J. Bligh" <Martin.Bligh@us.ibm.com>]

> I was just reading Bill's reply regaring rmap, and it
> seems to me that rmap is the most obvious and clean
> way to handle unmapping pages. So now I wonder why
> it wasn't done that way from the beginning?

Because it costs something to maintain the reverse map.
If the cost exceeds the benefit, it's not worth it. That's
why a bunch of us are working on bringing the cost down.
At the moment the cost is especially high on larger machines,
but we're getting there ... quickly ;-)

Martin.

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