From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753388Ab0AYU6r (ORCPT ); Mon, 25 Jan 2010 15:58:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753326Ab0AYU6p (ORCPT ); Mon, 25 Jan 2010 15:58:45 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:51947 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751852Ab0AYU6l (ORCPT ); Mon, 25 Jan 2010 15:58:41 -0500 From: "Rafael J. Wysocki" To: Shawn Starr Subject: Re: [Bug #14859] System timer firing too much without cause Date: Mon, 25 Jan 2010 21:59:33 +0100 User-Agent: KMail/1.12.3 (Linux/2.6.33-rc4-rjw; KDE/4.3.3; x86_64; ; ) Cc: Thomas Gleixner , Linux Kernel Mailing List , Kernel Testers List , "Jerome Glisse" References: <201001251230.23109.shawn.starr@rogers.com> In-Reply-To: <201001251230.23109.shawn.starr@rogers.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201001252159.33120.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 25 January 2010, Shawn Starr wrote: > On Monday 25 January 2010 12:20:38 Thomas Gleixner wrote: > > On Mon, 25 Jan 2010, Shawn Starr wrote: > > > On Monday 25 January 2010 05:35:50 Thomas Gleixner wrote: > > > > Shawn, why can't you use dynamic ticks ? In the bugzilla I just see > > > > that you worry about the IRQ0 interrupts (which are correct and > > > > necessary when the system is in nohz mode) and the extra rescheduling > > > > interrupts. How is the system misbehaving ? > > > > > > Well, this all stems from trying to use Radeon KMS with IRQs > > > on. Doing so I see system stalls and this is quite noticeable > > > however, I am able to show this same stall on the quad core with the > > > > x> same GPU. Right now, it is unclear to me if there is a underlying > > > > > irq issue or a bug in the radeon driver code that is showing these > > > stalls. Since the radeon folks - at the moment - do not think it is > > > a coding problem in their driver > > > > Does the stall go away, when you disable dynticks ? > > > > It does not, no. > > > > My impression was using dynamic ticks meant ticks were on demand and > > > > Dynamic ticks are providing a continuous tick long as the machine is > > busy. When a core becomes idle, we programm the timer to go off at the > > next scheduled timer event, if the event is longer away than the next > > tick. When the core goes out of idle (due to the timer or some other > > event) we restart the tick. > > > > So you see less timer interrupts (IRQ0 + Local timer interrupts) > > With dynamic ticks on or off, LOC increments rapidly, but I assume that is > normal behavour. > > So if none of this really is a kernel issue, I defer it to the radeon folks to > comment further. > > Please remove from regression list, I'll close the original bug. OK, closing it right now. Rafael