From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261478AbULIOut (ORCPT ); Thu, 9 Dec 2004 09:50:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261480AbULIOut (ORCPT ); Thu, 9 Dec 2004 09:50:49 -0500 Received: from mail3.utc.com ([192.249.46.192]:15357 "EHLO mail3.utc.com") by vger.kernel.org with ESMTP id S261478AbULIOul (ORCPT ); Thu, 9 Dec 2004 09:50:41 -0500 Message-ID: <41B86630.7030404@cybsft.com> Date: Thu, 09 Dec 2004 08:50:24 -0600 From: "K.R. Foley" Organization: Cybersoft Solutions, Inc. User-Agent: Mozilla Thunderbird 1.0 (X11/20041206) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Ingo Molnar CC: linux-kernel@vger.kernel.org, Lee Revell , Rui Nuno Capela , Mark_H_Johnson@Raytheon.com, Bill Huey , Adam Heath , Florian Schmidt , Thomas Gleixner , Michal Schmidt , Fernando Pablo Lopez-Lezcano , Karsten Wiese , Gunther Persoons , emann@mrv.com, Shane Shrybman , Amit Shah , Esben Nielsen Subject: Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-6 References: <20041122005411.GA19363@elte.hu> <20041123175823.GA8803@elte.hu> <20041124101626.GA31788@elte.hu> <20041203205807.GA25578@elte.hu> <20041207132927.GA4846@elte.hu> <20041207141123.GA12025@elte.hu> <41B6839B.4090403@cybsft.com> <20041208083447.GB7720@elte.hu> <41B726D1.6030009@cybsft.com> <41B7BC60.1060407@cybsft.com> <20041209121133.GB23077@elte.hu> In-Reply-To: <20041209121133.GB23077@elte.hu> X-Enigmail-Version: 0.89.5.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Ingo Molnar wrote: > * K.R. Foley wrote: > > >>OK dumb question. I am going out to get my own personal brown paper >>bag, since I seem to be wearing it so often. I forgot tasks get >>removed from the runqueue when they are sleeping, etc. so the active >>array should empty most of the time. However, with more RT tasks and >>interactive tasks being thrown back into the active queue I could see >>this POSSIBLY occasionally starving a few processes??? > > > interactive tasks do get thrown back, but they wont ever preempt RT > tasks. RT tasks themselves can starve any lower-prio process > indefinitely. Interactive tasks can starve other tasks up to a certain > limit, which is defined via STARVATION_LIMIT, at which point we empty > the active array and perform an array switch. (also see > EXPIRED_STARVING()) > > Ingo > Understood. BTW, I wouldn't consider some possible starvation of lower priority, non-realtime tasks to be incorrect behavior for a realtime system. The comments in the above email as well as previous emails were not intended as complaints or questions of correctness. They were more just thoughts generated while thinking about some of the reports of non-realtime tasks being starved. kr