From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763247AbYBEXiZ (ORCPT ); Tue, 5 Feb 2008 18:38:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756843AbYBEXiQ (ORCPT ); Tue, 5 Feb 2008 18:38:16 -0500 Received: from ithilien.qualcomm.com ([129.46.51.59]:56189 "EHLO ithilien.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752991AbYBEXiQ (ORCPT ); Tue, 5 Feb 2008 18:38:16 -0500 Message-ID: <47A8F328.5070107@qualcomm.com> Date: Tue, 05 Feb 2008 15:37:12 -0800 From: Max Krasnyanskiy User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Peter Zijlstra , Steven Rostedt , Ingo Molnar CC: LKML Subject: RT scheduler config, suggestions and questions Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Folks, I just realized that in latest Linus' tree following sysctls are under SCHED_DEBUG: sched_rt_period sched_rt_ratio I do not believe that is correct. I know that we do not want to expose scheduler knobs in general but theses are not the heuristic kind of knobs. There is no way the scheduler can magically figure out what the correct setting should be here. Also shouldn't those new RT features that recently went be configurable and _disabled_ by default ? For example "RT watchdog" and "RT throttling" actually seem very questionable. SCHED_FIFO is clearly defined as " A SCHED_FIFO process runs until either it is blocked by an I/O request, it is preempted by a higher priority process, or it calls sched_yield(2). " Both the watchdog and the throttling are clearly braking that rule. I think it's good to have those features but not enabled by default and certainly not with sysctls that disable them hidden under debugging. How about this: - We introduce Kconfig options for them ? - Expose all rt sysctls outside of #ifdef DEBUG I can kook up some patches if that sounds ok. ---- btw I can see "watchdog" being very useful to catch hard-RT tasks that exceed the deadline. But's it gotta be per thread. Single setting per user is not enough. Unless a use has a single RT task. Max