From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030803AbXDLXl5 (ORCPT ); Thu, 12 Apr 2007 19:41:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030805AbXDLXl5 (ORCPT ); Thu, 12 Apr 2007 19:41:57 -0400 Received: from holomorphy.com ([66.93.40.71]:35604 "EHLO holomorphy.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030803AbXDLXl4 (ORCPT ); Thu, 12 Apr 2007 19:41:56 -0400 Date: Thu, 12 Apr 2007 16:42:09 -0700 From: William Lee Irwin III To: Andrew Morton Cc: Matt Mackall , linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/13] maps: pagemap, kpagemap, and related cleanups Message-ID: <20070412234209.GO2986@holomorphy.com> References: <1.486631555@selenic.com> <20070412231050.GN2986@holomorphy.com> <20070412163235.dd030637.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070412163235.dd030637.akpm@linux-foundation.org> Organization: The Domain of Holomorphy User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 12 Apr 2007 16:10:50 -0700 William Lee Irwin III wrote: >> This solves a real-life problem for Oracle system monitoring software >> (specifically EM). Among the tasks it must carry out is determining >> per-process memory footprint of a set of cooperating tasks (i.e. Oracle >> processes). RSS is inadequate for this due to page sharing; this work >> provides sufficient information to determine what EM needs. On Thu, Apr 12, 2007 at 04:32:35PM -0700, Andrew Morton wrote: > Not a good idea to expose raw flags in this manner - it changes at the drop > of a hat. We'd need to also expose the kernel's PG_foo-to-bitnumber > mapping to make this viable. > Not a good idea to use page->_count: page_count() will be more stable. > Otherwise OK, I guess: the interpretation of the page refcount is unlikely > to change much over time. EM wants to determine page_mapcount() for the most part for the purposes of determining "uniquely attributable RSS" (my ca. 2004 nomenclature) or "proportional RSS" (mpm's more recent nomenclature); as things now stand it will have to infer them by maintaining a table of pfn's and mappings thereof, but at least that can be done with it. -- wli