From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933365AbXLNNFB (ORCPT ); Fri, 14 Dec 2007 08:05:01 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765624AbXLNNEx (ORCPT ); Fri, 14 Dec 2007 08:04:53 -0500 Received: from [194.117.236.238] ([194.117.236.238]:35785 "EHLO heracles.linux360.ro" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1765468AbXLNNEw (ORCPT ); Fri, 14 Dec 2007 08:04:52 -0500 Date: Fri, 14 Dec 2007 18:01:19 +0200 From: Eduard-Gabriel Munteanu To: Andi Kleen Cc: LKML , Thomas Gleixner Subject: Re: [PATCH] Option to disable AMD C1E (allows dynticks to work) Message-ID: <20071214180119.4c492f6c@linux360.ro> In-Reply-To: <20071214122048.GA12550@one.firstfloor.org> References: <20071214004442.5f9eba88@linux360.ro> <20071214143941.2c7dcfb4@linux360.ro> <20071214101720.GA10981@one.firstfloor.org> <20071214154106.4f0b2d8c@linux360.ro> <20071214122048.GA12550@one.firstfloor.org> 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 Fri, 14 Dec 2007 13:20:48 +0100 Andi Kleen wrote: > AMD doesn't support states deeper than C1 on multi core currently, so > in general they don't matter much right now. Thanks for the info, I wasn't aware of this. > The better solution there is to use HPET instead. Newer systems > generally have HPET already enabled in the BIOS and for older systems > hpet=force gains more and more support. So try that. Dynticks won't use the HPET, even if enabled. IIRC, HPET is enabled on my system (NVIDIA MCP51) even without "hpet=force". Here's dmesg's output on Linux 2.6.24-rc5: $ dmesg | grep -Ei "(lapic|hpet|disabling)"Command line: ro hpet=force ACPI: HPET 3FFA9730, 0038 (r1 A M I OEMHPET0 2000727 MSFT 97) ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled) ACPI: LAPIC (acpi_id[0x02] lapic_id[0x01] enabled) ACPI: HPET id: 0x10de8201 base: 0xfed00000 Kernel command line: ro hpet=force hpet clockevent registered TSC calibrated against HPET Disabling APIC timer 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. Unpacking initramfs...<6>Clockevents: could not switch to one-shot mode:<6>Clockevents: could not switch to one-shot mode: lapic is not functional. lapic is not functional. hpet_resources: 0xfed00000 is busy LAPIC is seemingly disabled (C1E detection code does this), but clockevents still tries to use it, instead of relying on HPET. I'll look into this, but please give me a heads up if you know more about what's happening. Looks like fixing this is better than using LAPIC for dynticks (and disabling C1E) on such systems.