Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753776Ab1CYOjO (ORCPT ); Fri, 25 Mar 2011 10:39:14 -0400 Received: from claw.goop.org ([74.207.240.146]:52436 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753609Ab1CYOjN (ORCPT ); Fri, 25 Mar 2011 10:39:13 -0400 Message-ID: <4D8CA902.7090907@goop.org> Date: Fri, 25 Mar 2011 14:38:58 +0000 From: Jeremy Fitzhardinge User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110307 Fedora/3.1.9-0.39.b3pre.fc14 Lightning/1.0b3pre Thunderbird/3.1.9 MIME-Version: 1.0 To: Konrad Rzeszutek Wilk CC: Len Brown , venki@google.com, ak@linux.intel.com, suresh.b.siddha@intel.com, sfr@canb.auug.org.au, peterz@infradead.org, benh@kernel.crashing.org, linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, arjan@linux.intel.com, Trinabh Gupta Subject: Re: [Xen-devel] Re: [RFC PATCH V4 4/5] cpuidle: driver for xen References: <20110322123208.28725.30945.stgit@tringupt.in.ibm.com> <20110322123324.28725.3131.stgit@tringupt.in.ibm.com> <20110322145054.GB26952@dumpdata.com> <4D89C40B.4020809@linux.vnet.ibm.com> <20110324120522.GB29294@dumpdata.com> In-Reply-To: <20110324120522.GB29294@dumpdata.com> X-Enigmail-Version: 1.1.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1208 Lines: 33 On 03/24/2011 12:05 PM, Konrad Rzeszutek Wilk wrote: > On Thu, Mar 24, 2011 at 03:18:14AM -0400, Len Brown wrote: >> Is a CONFIG_XEN kernel supposed to use just HLT in idle? > For right now.. For always, I should think. >> xen_arch_setup() does this: >> >> pm_idle = default_idle; >> boot_option_idle_override = IDLE_HALT; >> >> which has that effect. I guess this makes sense b/c the >> CONFIG_XEN kernel is Dom0 and the real C-sates are done >> by the hypervisor? > Correct. There are some patches that make the C-states > be visible in the Linux kernel, but that hasn't been ported > over yet. All we need is for the idle CPU to block in the hypervisor; a plain "hlt" is always going to be sufficient (which is overridden as a pvop into a sched_idle hypercall). Xen will choose an appropriate power state for the physical cpus depending on the overall busyness of the system (which any individual virtual machine can't determine). J -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/