From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751186AbWGDINT (ORCPT ); Tue, 4 Jul 2006 04:13:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751189AbWGDINT (ORCPT ); Tue, 4 Jul 2006 04:13:19 -0400 Received: from omx1-ext.sgi.com ([192.48.179.11]:40338 "EHLO omx1.americas.sgi.com") by vger.kernel.org with ESMTP id S1751186AbWGDINS (ORCPT ); Tue, 4 Jul 2006 04:13:18 -0400 Message-ID: <44AA2301.2030400@sgi.com> Date: Tue, 04 Jul 2006 10:12:49 +0200 From: Jes Sorensen User-Agent: Thunderbird 1.5.0.4 (X11/20060527) MIME-Version: 1.0 To: Arjan van de Ven CC: Milton Miller , Jens Axboe , linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [patch] reduce IPI noise due to /dev/cdrom open/close References: <200607040516.k645GFTj014564@sullivan.realtime.net> <44AA1D09.7080308@sgi.com> <1151999591.3109.8.camel@laptopd505.fenrus.org> In-Reply-To: <1151999591.3109.8.camel@laptopd505.fenrus.org> X-Enigmail-Version: 0.94.0.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Arjan van de Ven wrote: > On Tue, 2006-07-04 at 09:47 +0200, Jes Sorensen wrote: >> Well yes and no. $#@$#@* hald will do the open/close stupidity a >> couple of times per second. On a 128 CPU system thats quite a lot of >> IPI traffic, resulting in measurable noise if you run a benchmark. >> Remember that the IPIs are synchronous so you have to wait for them to >> hit across the system : > > can you get hald fixed? That sounds important anyway... stupid userspace > isn't going to be good no matter what, and the question is how much crap > we need to do in the kernel to compensate for stupid userspace... > especially if such userspace is open source and CAN be fixed... I'd like to, I don't know how feasible it is though :( The distros make it a priority to run all the GUI stuff that makes Linux look like windows as much as they can, which includes autodetecting when users insert their latest audio CD so they can launch the mp3 ripper automatically .... Guess the question is, is there a way we can detect when media has been inserted without doing open/close on the device constantly? It's not something I have looked at in detail, so I dunno if there's a sensible way to handle it. The other part of it is that I do think it's undesirable that a user space app can cause so much kernel IPI noise by simply doing open/close on a device. Anyway, I do agree, we should look at fixing both problems. Cheers, Jes