From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764780AbXLNJnW (ORCPT ); Fri, 14 Dec 2007 04:43:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758524AbXLNJnN (ORCPT ); Fri, 14 Dec 2007 04:43:13 -0500 Received: from [194.117.236.238] ([194.117.236.238]:56065 "EHLO heracles.linux360.ro" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752800AbXLNJnM (ORCPT ); Fri, 14 Dec 2007 04:43:12 -0500 Date: Fri, 14 Dec 2007 14:39:41 +0200 From: Eduard-Gabriel Munteanu To: Andi Kleen Cc: LKML Subject: Re: [PATCH] Option to disable AMD C1E (allows dynticks to work) Message-ID: <20071214143941.2c7dcfb4@linux360.ro> In-Reply-To: References: <20071214004442.5f9eba88@linux360.ro> X-Mailer: Claws Mail 3.0.2 (GTK+ 2.10.14; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 13 Dec 2007 23:33:07 +0100 Andi Kleen wrote: > The description/option is not correct. The mainline kernel never > disables C1e. Some distribution kernels and Xen do, perhaps you're > confusing this with them. > > You would rather need a "force_disable_c1e" option if anything. The option I added (which is set to Y by default, but that's another matter) disables C1E without any other kernel parameter. In my opinion, this should be the normal behavior: the kernel has both SMP and NO_HZ enabled, so do whatever is necessary to enable dynticks. But it would also be useful, for benchmarking purposes, to prevent the kernel from disabling C1E using a kernel parameter; that's what force_amd_c1e does. > Anyways this should be near all obsolete with forced HPET. With HPET > dynticks can be used even with C1e. So in most cases you can just > use hpet=force instead and get dynticks and C1e together. On my system, hpet=force does not enable dynticks: $ dmesg | grep -E "(not functional|hpet)" Command line: ro hpet=force Kernel command line: ro hpet=force hpet clockevent registered hpet0: at MMIO 0xfed00000, IRQs 2, 8, 31 hpet0: 3 32-bit timers, 25000000 Hz Time: hpet clocksource has been installed. Clockevents: could not switch to one-shot mode: lapic is not functional. Clockevents: could not switch to one-shot mode: lapic is not functional. hpet_resources: 0xfed00000 is busy But, using this patch, the kernel enables dynticks.