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

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Message-Id: <1173264462.6374.140.camel@twins>
Date:	Wed, 07 Mar 2007 11:47:42 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Miklos Szeredi <miklos@...redi.hu>, akpm@...ux-foundation.org,
	mingo@...e.hu, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	benh@...nel.crashing.org
Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes
	nonlinear)

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.

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