From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Hancock Subject: Re: Regression on VIA C3 motherboard, commit: 66f2173e2 Date: Fri, 06 Feb 2009 08:46:31 -0600 Message-ID: <498C4D47.4040201@gmail.com> References: <498A93E5.2080509@candelatech.com> <498B8547.1010803@gmail.com> <498BD448.80102@candelatech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Len Brown To: Ben Greear Return-path: Received: from an-out-0708.google.com ([209.85.132.243]:33500 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750945AbZBFOqf (ORCPT ); Fri, 6 Feb 2009 09:46:35 -0500 In-Reply-To: <498BD448.80102@candelatech.com> Sender: netdev-owner@vger.kernel.org List-ID: Ben Greear wrote: > Robert Hancock wrote: >> Ben Greear wrote: >>> I have a via motherboard with C3 processor and some real-tek NICs. I >>> noticed >>> when using the top-of-tree that performance on it sucked (30Mbps v/s >>> 54Mbps >>> network throughput in one pertinent test). >>> >>> After several hours of bisecting, I see this as the culprit: >>> >>> 7b37b5fd9ba32c0c5afc3537eed7e7466f2173e2 is first bad commit >>> commit 7b37b5fd9ba32c0c5afc3537eed7e7466f2173e2 >>> Author: Len Brown >>> Date: Tue Dec 23 01:47:42 2008 -0500 >>> >>> ACPI: disable MPS when NO APIC-table found >>> When ACPI is asked to find an MADT (APIC table) >>> and fails, then ACPI expects to run in PIC mode. >>> However, if an MP Table is was found, IRQs will be >>> registered as if an IOAPIC is being used, even >>> though ACPI is configuring interrupt links links for PIC mode. >>> In this scenario, disable MPS so that IRQs >>> are registered in PIC mode, consistent with ACPI. >>> http://bugzilla.kernel.org/show_bug.cgi?id=12257 >>> Signed-off-by: Len Brown >>> >>> :040000 040000 86ce74daee3a9fe6ff21ef7f8fb364af23ec0c1e >>> 364933dfec0df34e63b1aeff6aff4092d421886b M arch >>> >>> >>> In addition, I see this warning in my logs, which is likely the symptom: >>> >>> ACPI Exception (tbxface-0627): AE_NO_ACPI_TABLES, While loading >>> namespace from ACPI tables ] >>> ACPI: Unable to load the System Description Tables >> >> You're getting this on boot: >> >> ACPI Error (tbxfroot-0218): A valid RSDP was not found [20080926] >> >> That essentially means ACPI isn't working at all, I think. Did >> previous kernels produce this error? Do you have ACPI disabled in the >> BIOS or something? >> > Er, yes...I have ACPI disabled in the BIOS. I seem to recall now that > it worked around > some instability, but it's been a few years since we set that up. > Still, it was working > fine before, and fine again when I comment out the change in this commit > (and another > change to force the 'tsc' to be considered stable). > > The same error message happens as far back as 2.6.25 at least. It seems like this is a slightly different case than the patch is trying to address. It's talking about just the MADT not being found, when in your case we have no ACPI at all. However, I should point out that in general, disabling ACPI tends to be a bad idea, since it tends to bring out untested code paths both in the kernel and in the BIOS/hardware. (For one thing it means you can't use the PM timer, which is likely why your system is falling back to jiffies timing.)