From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261199AbVFFH6D (ORCPT ); Mon, 6 Jun 2005 03:58:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261204AbVFFH6D (ORCPT ); Mon, 6 Jun 2005 03:58:03 -0400 Received: from mx1.elte.hu ([157.181.1.137]:29655 "EHLO mx1.elte.hu") by vger.kernel.org with ESMTP id S261199AbVFFH55 (ORCPT ); Mon, 6 Jun 2005 03:57:57 -0400 Date: Mon, 6 Jun 2005 09:57:28 +0200 From: Ingo Molnar To: "Perez-Gonzalez, Inaky" Cc: Esben Nielsen , Thomas Gleixner , linux-kernel@vger.kernel.org, Daniel Walker , Oleg Nesterov Subject: Re: [patch] Real-Time Preemption, plist fixes Message-ID: <20050606075728.GA13088@elte.hu> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Perez-Gonzalez, Inaky wrote: > >From: Ingo Molnar [mailto:mingo@elte.hu] > > > >so the question is - can we have an extreme (larger than 140) number of > >RT tasks? If yes, why are they all RT - they can have no expectation of > >good latencies with a possible load factor of 140! > > In practice, didn't we want most tasks to behave like RT? (for > interactivity purposes) -- I recall hearing that's basically what good > interactivity meant; short reponse times to events. that's not what the current code does (and it's not what the non-plist code did either). We dont do PI handling for non-RT tasks. They basically have no RT expectations at all, and including them in the PI mechanism would only slow them down, and would increase the latencies of the RT tasks as well. But indeed it could improve interactivity (but this has not been proven yet) - and also for testing purposes it would sure be useful, so we should perhaps make ALL_TASKS_PI default-on, as Daniel suggests. If that is done then plists are indeed a superior solution. But if in the end we decide to only include RT tasks in the PI mechanism (which could easily happen) then there seems to be little practical difference between sorted lists and plists. Ingo