From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750861AbWDFDZK (ORCPT ); Wed, 5 Apr 2006 23:25:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751350AbWDFDZK (ORCPT ); Wed, 5 Apr 2006 23:25:10 -0400 Received: from dvhart.com ([64.146.134.43]:36806 "EHLO dvhart.com") by vger.kernel.org with ESMTP id S1750861AbWDFDZJ (ORCPT ); Wed, 5 Apr 2006 23:25:09 -0400 From: Darren Hart To: linux-kernel@vger.kernel.org Subject: RT task scheduling User-Agent: KMail/1.8.3 Cc: Ingo Molnar , Thomas Gleixner , "Stultz, John" , Peter Williams , "Siddha, Suresh B" , Nick Piggin MIME-Version: 1.0 Date: Wed, 5 Apr 2006 20:25:04 -0700 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200604052025.05679.darren@dvhart.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org My last mail specifically addresses preempt-rt, but I'd like to know people's thoughts regarding this issue in the mainline kernel. Please see my previous post "realtime-preempt scheduling - rt_overload behavior" for a testcase that produces unpredictable scheduling results. Part of the issue here is to define what we consider "correct behavior" for SCHED_FIFO realtime tasks. Do we (A) need to strive for "strict realtime priority scheduling" where the NR_CPUS highest priority runnable SCHED_FIFO tasks are _always_ running? Or do we (B) take the best effort approach with an upper limit RT priority imbalances, where an imbalance may occur (say at wakeup or exit) but will be remedied within 1 tick. The smpnice patches improve load balancing, but don't provide (A). More details in the previous mail... Thanks, --Darren