Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756438AbZKJOez (ORCPT ); Tue, 10 Nov 2009 09:34:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756246AbZKJOey (ORCPT ); Tue, 10 Nov 2009 09:34:54 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:59896 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756183AbZKJOex (ORCPT ); Tue, 10 Nov 2009 09:34:53 -0500 Subject: Re: [PATCH] DRTL kernel 2.6.32-rc3 : SCHED_EDF, DI RT-Mutex, Deadline Based Interrupt Handlers From: Peter Zijlstra To: Raistlin Cc: Soumya K S , linux-kernel@vger.kernel.org, mingo@redhat.com, Dhaval Giani , Thomas Gleixner , Claudio Scordino , michael trimarchi , Juri Lelli In-Reply-To: <1256747090.25821.367.camel@Palantir> References: <1256198088.6700.76.camel@Palantir> <1256460376.15273.31.camel@Palantir> <1256747090.25821.367.camel@Palantir> Content-Type: text/plain; charset="UTF-8" Date: Tue, 10 Nov 2009 15:34:48 +0100 Message-ID: <1257863689.4108.441.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1654 Lines: 40 On Wed, 2009-10-28 at 17:24 +0100, Raistlin wrote: > Relying on userspace to do things > 'intelligently' is something I'm not sure I would do, especially in a so > much general purpose OS like Linux, used in so much different contexts. > But, again, that's only my opinion. :-) I'd put it even stronger, relying on userspace to do something intelligent is utterly stupid. We have to assume userspace is hostile and out to get you. Therefore I fully support the model that puts admission control into the kernel, because that provides isolation between, and guarantees to applications. Not providing this, and having no overload protection is one of the biggest failures of SCHED_FIFO/RR. On Tue, 2009-11-10 at 19:33 +0530, Soumya K S wrote: > Hmm I guess you too are "totally" dependent on user giving you the > right parameters _intelligently_ (deadline / budget)... I guess we are > not too different there expecting the users to be _aware_ ..! The difference is that if A messes up its own parameters only A suffers and the rest of the system continues to work as expected. With your approach anything is out the window. So yes, userspace needs to be aware, but a task can only screw itself, not everybody else, which is a very important feature. @ DRTL folks: If you want deadline based scheduling (it appears you do) I suggest you start helping out Dario, your proposal isn't going to happen. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/