From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Re: Wishlist: Disable C6 in intel_idle for Model 44 processors Date: Wed, 12 Jun 2013 19:32:49 +0100 Message-ID: <20130612183249.GA20957@srcf.ucam.org> References: <38D8523B-C50E-4D81-A9E2-526292B19AF3@usgs.gov> <20130612134002.GA15317@srcf.ucam.org> <1BD2BF18-8FAA-4633-8B6D-7CA2D6AE67AC@usgs.gov> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from cavan.codon.org.uk ([93.93.128.6]:57367 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756019Ab3FLScw (ORCPT ); Wed, 12 Jun 2013 14:32:52 -0400 Content-Disposition: inline In-Reply-To: <1BD2BF18-8FAA-4633-8B6D-7CA2D6AE67AC@usgs.gov> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Larry Baker Cc: linux-acpi@vger.kernel.org, Rob E Russell On Wed, Jun 12, 2013 at 11:11:21AM -0700, Larry Baker wrote: > The processor errata is operating system agnostic. I suspect the BIOS > workaround they envision would be a feature in the BIOS to limit the > choice of C states to be used. The IBM BIOS has such a setting, and > the default value is to completely disable C states. However, > intel_idle ignores the BIOS setting. No, the BIOS workaround will typically be to program the memory controller such that the problem isn't triggered. If you're having latency-related issues then the appropriate fix is to use the pm_qos interface that's present in RHEL 6 and the upstream kernel, and you can do so in RHEL using the ktune command. -- Matthew Garrett | mjg59@srcf.ucam.org