From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030521AbXCGLAq (ORCPT ); Wed, 7 Mar 2007 06:00:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030626AbXCGLAq (ORCPT ); Wed, 7 Mar 2007 06:00:46 -0500 Received: from cantor2.suse.de ([195.135.220.15]:46605 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030521AbXCGLAp (ORCPT ); Wed, 7 Mar 2007 06:00:45 -0500 Date: Wed, 7 Mar 2007 12:00:36 +0100 From: Nick Piggin To: Peter Zijlstra Cc: Miklos Szeredi , akpm@linux-foundation.org, mingo@elte.hu, linux-mm@kvack.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear) Message-ID: <20070307110035.GE5555@wotan.suse.de> References: <20070307010756.b31c8190.akpm@linux-foundation.org> <1173259942.6374.125.camel@twins> <20070307094503.GD8609@wotan.suse.de> <20070307100430.GA5080@wotan.suse.de> <1173262002.6374.128.camel@twins> <20070307102106.GB5555@wotan.suse.de> <1173263085.6374.132.camel@twins> <20070307103842.GD5555@wotan.suse.de> <1173264462.6374.140.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1173264462.6374.140.camel@twins> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 07, 2007 at 11:47:42AM +0100, Peter Zijlstra wrote: > 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. Sorry, I didn't understand your misunderstandings ;) > > > 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. But so could nonlinear page reclaim. I think we need to restrict nonlinear mappings to root if we're worried about that.