From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756618AbYAJAnT (ORCPT ); Wed, 9 Jan 2008 19:43:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752431AbYAJAnM (ORCPT ); Wed, 9 Jan 2008 19:43:12 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:55980 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750962AbYAJAnK (ORCPT ); Wed, 9 Jan 2008 19:43:10 -0500 Date: Wed, 9 Jan 2008 16:42:41 -0800 From: Arjan van de Ven To: Christoph Hellwig Cc: Benjamin Herrenschmidt , Christoph Hellwig , Pavel Roskin , Dave Airlie , Pekka Paalanen , linux-kernel@vger.kernel.org, jbeulich@novell.com Subject: Re: Replacement for page fault notifiers? Message-ID: <20080109164241.7daa5770@laptopd505.fenrus.org> In-Reply-To: <20080109202254.GA5279@infradead.org> References: <20080108210638.5c9e093a@daedalus.pq.iki.fi> <20080108203235.GA772@infradead.org> <21d7e9970801081413n307ab07aq462a9fff014143ae@mail.gmail.com> <1199838407.6734.83.camel@pasglop> <1199902724.8050.11.camel@dv> <20080109182157.GA32754@infradead.org> <1199908703.6734.133.camel@pasglop> <20080109202254.GA5279@infradead.org> Organization: Intel X-Mailer: Claws Mail 3.0.2 (GTK+ 2.12.1; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 9 Jan 2008 20:22:54 +0000 Christoph Hellwig wrote: > On Thu, Jan 10, 2008 at 06:58:23AM +1100, Benjamin Herrenschmidt > wrote: > > It's a sane thing to do, Christoph, I don't think it's a > > unreasonable request to put the hooks back in. > > As said a few times before there's simply no way we're going to put > exactly that crap back. For one the patch removed a whole lot of > crud from the kprobes code that simply isn't going to come back just > because there are some pagefault notifiers. Second the page fault > notifiers were horribly implemented and quite inefficient. And third > we're not going to put something in just for out of tree code. > I'm btw all in favor of making mmio tracing full fledged kernel infrastructure. This doesn't mean "notifier" imo; this means a real flag in the struct page, and then the page fault code can do if (page->flags & FLAG_MMIO_TRACED) mmio_trace(page, regs, whatever..); (probably surrounded by a CONFIG_ ifdef) THis is a TON lighter than a notifier chain, and actually what you want, you don't really want a notifier, you want a call back when a special kind of page is touched. -- If you want to reach me at my work email, use arjan@linux.intel.com For development, discussion and tips for power savings, visit http://www.lesswatts.org