From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030246AbVHKLAv (ORCPT ); Thu, 11 Aug 2005 07:00:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030262AbVHKLAu (ORCPT ); Thu, 11 Aug 2005 07:00:50 -0400 Received: from mx2.elte.hu ([157.181.151.9]:55946 "EHLO mx2.elte.hu") by vger.kernel.org with ESMTP id S1030246AbVHKLAt (ORCPT ); Thu, 11 Aug 2005 07:00:49 -0400 Date: Thu, 11 Aug 2005 13:00:51 +0200 From: Ingo Molnar To: linux-kernel@vger.kernel.org Cc: Thomas Gleixner , "Paul E. McKenney" , george anzinger Subject: [patch] Real-Time Preemption, -RT-2.6.13-rc4-V0.7.53-01, High Resolution Timers & RCU-tasklist features Message-ID: <20050811110051.GA20872@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 i have released the -53-01 Real-Time Preemption patch, which can be downloaded from: http://redhat.com/~mingo/realtime-preempt/ there are two new features in this release, which justified the jump from .52 to .53: - the inclusion of the High Resolution Timers patch, written by George Anzinger, and ported/improved/cleaned-up by Thomas Gleixner. - the inclusion of the RCU tasklist_lock patch from Paul McKenney. the HRT patch from George Anzinger is a crutial piece of real-time infrastructure. The version included in the -RT tree supports both PIT and local APIC timer driven variable-rate timer interrupts. Thomas Glexiner, besides porting it to PREEMPT_RT, cleaning it up, adding the local APIC timer support has also added the CONFIG_HIGH_RES_TIMERS_DYN_PRIO feature, which pushes priority inheritance into the high-res timer space. Furthermore, Thomas has extended nanosleep to use HR timers, if the task is RT. This makes it easier to test HRT functionality. NOTE: there's a new softirq, softirq-hrtimer (PID 8 on UP x86), which should be chrt-ed to higher than SCHED_FIFO-50 if HR timer interrupts are the most important latencies in the system. E.g.: chrt -f 90 -p 8 the RCU tasklist-lock patch is a small but important feature from Paul McKenney which enables good HRT latencies: the HRT patch, when using POSIX timers, would use a signal-sending codepath that depends on the tasklist_lock, and thus the (quite high) tasklist_lock latencies controlled the latency of HR timers - defeating much of the benefits of HR timers. With the RCU tasklist-lock the signal sending path is now RCU-read locked, with no locking dependency, and thus excellent worst-case latencies. given these changes, some (mostly build-related) regressions are to be expected. Only the x86 architecture is expected to work for now. to build a -V0.7.53-01 tree, the following patches should to be applied: http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.12.tar.bz2 http://kernel.org/pub/linux/kernel/v2.6/testing/patch-2.6.13-rc4.bz2 http://redhat.com/~mingo/realtime-preempt/realtime-preempt-2.6.13-rc4-RT-V0.7.53-01 patches, bugreports and any other feedback welcome, Ingo