From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751048AbXDMBvO (ORCPT ); Thu, 12 Apr 2007 21:51:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751149AbXDMBvO (ORCPT ); Thu, 12 Apr 2007 21:51:14 -0400 Received: from waste.org ([66.93.16.53]:59700 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751048AbXDMBvN (ORCPT ); Thu, 12 Apr 2007 21:51:13 -0400 Date: Thu, 12 Apr 2007 20:38:40 -0500 From: Matt Mackall To: Nick Piggin Cc: Andrew Morton , William Lee Irwin III , linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/13] maps: pagemap, kpagemap, and related cleanups Message-ID: <20070413013840.GK11115@waste.org> References: <1.486631555@selenic.com> <20070412231050.GN2986@holomorphy.com> <20070412163235.dd030637.akpm@linux-foundation.org> <461ECB9C.8060000@yahoo.com.au> <20070413002538.GJ11115@waste.org> <461ED675.3060909@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <461ED675.3060909@yahoo.com.au> 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 Fri, Apr 13, 2007 at 11:01:41AM +1000, Nick Piggin wrote: > >Basically: to show what the hell's going on in the VM. > > kprobes / systemtap isn't good enough? It's not really a good match to the kprobes model. I'm not interested in events, per se. I don't want to need to know about every single alloc/free of N different varieties integrated from boot onward to build up an image of the state of the system. Instead, I want to take snapshots of the state of the VM. The main goal here is to be able to answer the question "where's my memory going?". Currently you can't really give a good answer to that question from userspace because of shared mappings, etc. There are lots of secondary questions that follow on very quickly from that, like "what parts of my shared mappings are or aren't shared, and why?", "what's actually in my application's working set?" and "how much of this crap can I ditch?". -- Mathematics is the supreme nostalgia of our time.