From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261795AbTDED7U (for ); Fri, 4 Apr 2003 22:59:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261796AbTDED7U (for ); Fri, 4 Apr 2003 22:59:20 -0500 Received: from holomorphy.com ([66.224.33.161]:46740 "EHLO holomorphy") by vger.kernel.org with ESMTP id S261795AbTDED7T (for ); Fri, 4 Apr 2003 22:59:19 -0500 Date: Fri, 4 Apr 2003 20:10:18 -0800 From: William Lee Irwin III To: Rik van Riel Cc: Andrea Arcangeli , "Martin J. Bligh" , Andrew Morton , mingo@elte.hu, hugh@veritas.com, dmccr@us.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: objrmap and vmtruncate Message-ID: <20030405041018.GG993@holomorphy.com> Mail-Followup-To: William Lee Irwin III , Rik van Riel , Andrea Arcangeli , "Martin J. Bligh" , Andrew Morton , mingo@elte.hu, hugh@veritas.com, dmccr@us.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20030405024414.GP16293@dualathlon.random> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.3.28i Organization: The Domain of Holomorphy Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 04, 2003 at 10:59:59PM -0500, Rik van Riel wrote: > The only issues with objrmap seems to be mremap, which Hugh > seems to have taken care of, and the case of a large number > of processes mapping different parts of the same file multiple > times (1000 processes mapping each 1000 parts of the same file), > which would grow the complexity of the VMA search from linear > to quadratical. > That last case is also fixable, though, probably best done using > k-d trees. > Except for nonlinear VMAs I don't think there are any big obstacles > left that would keep us from switching to object rmap. The k-d trees only solve the "external" interference case, that is, it thins the search space by eliminating vma's the page must necessarily be outside of. They don't solve the "internal" interference case, where the page does fall into all of the vma's, but only a few out of those have actually faulted the page into the pagetables. This is likely only "fixable" by pointwise methods, which seem to come with notable maintenance expense. -- wli