Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear)

Peter Zijlstra
2007-03-07T10:49:16Z

On Wed, 2007-03-07 at 11:38 +0100, Nick Piggin wrote:

> > > There are real users who want these fast, though.
> >
> > Yeah, why don't we have a tree per nonlinear vma to find these pages?
> >
> > wli mentions shadow page tables..
>
> We could do something more efficient, but I thought that half the point
> was that they didn't carry any of this extra memory, and they could be
> really fast to set up at the expense of efficiency elsewhere.

I'm failing to understand this :-(

That extra memory, and apparently they don't want the inefficiency
either.

> I don't see it being a big deal. I doubt anybody is writing out huge
> amounts of data via nonlinear mappings.

Well, now they don't, but it could be done or even exploited as a DoS.