From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754008AbXDMOIq (ORCPT ); Fri, 13 Apr 2007 10:08:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754009AbXDMOIq (ORCPT ); Fri, 13 Apr 2007 10:08:46 -0400 Received: from thunk.org ([69.25.196.29]:46119 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754008AbXDMOIq (ORCPT ); Fri, 13 Apr 2007 10:08:46 -0400 Date: Fri, 13 Apr 2007 10:08:27 -0400 From: Theodore Tso To: Nick Piggin Cc: Andrew Morton , William Lee Irwin III , Matt Mackall , linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/13] maps: pagemap, kpagemap, and related cleanups Message-ID: <20070413140827.GA8864@thunk.org> Mail-Followup-To: Theodore Tso , Nick Piggin , Andrew Morton , William Lee Irwin III , Matt Mackall , linux-kernel@vger.kernel.org References: <20070412163235.dd030637.akpm@linux-foundation.org> <461ECB9C.8060000@yahoo.com.au> <20070412174201.065068b2.akpm@linux-foundation.org> <461ED96C.5030606@yahoo.com.au> <20070412182213.a18cc4a7.akpm@linux-foundation.org> <461EE005.6070605@yahoo.com.au> <20070412185723.5a5f0443.akpm@linux-foundation.org> <461EE890.2040601@yahoo.com.au> <20070412193255.62a0b8ed.akpm@linux-foundation.org> <461EFB98.8050408@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <461EFB98.8050408@yahoo.com.au> User-Agent: Mutt/1.5.13 (2006-08-11) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on thunker.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 13, 2007 at 01:40:08PM +1000, Nick Piggin wrote: > With systemtap scripts, you could walk pagetables and print *the exact > page information you want*, or you could walk pfns, or LRU, or page_tree, > or walk the page tree then the rmap structures. And you can selectively > cull out items you don't care about if you only care about a subset of > items, based on arbitrary criteria. And you can most likely do all that > more efficiently than with a conglomeration of various /proc files > (assuming they even provide what you want in the first place). Yes, but maintaining the systemtap scripts will be a nightmare, since they would be outside the kernel, and as we change our internal data structure, the scripts would become useless. This is a fundamental problem with systemtap that we haven't been able to solve yet, because solving it would freeze various internal data structures or kernel functions. I agree that's not acceptable; which is why I don't think systemtap would be a good match for the problem we're trying to solve here. - Ted