Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752182AbWCPAAT (ORCPT ); Wed, 15 Mar 2006 19:00:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752187AbWCPAAT (ORCPT ); Wed, 15 Mar 2006 19:00:19 -0500 Received: from mailout1.vmware.com ([65.113.40.130]:38413 "EHLO mailout1.vmware.com") by vger.kernel.org with ESMTP id S1752184AbWCPAAR (ORCPT ); Wed, 15 Mar 2006 19:00:17 -0500 Message-ID: <4418AA64.7030306@vmware.com> Date: Wed, 15 Mar 2006 15:59:32 -0800 From: Dan Hecht User-Agent: Thunderbird 1.5 (X11/20051201) MIME-Version: 1.0 To: Pavel Machek Cc: Zachary Amsden , Linus Torvalds , Linux Kernel Mailing List , Virtualization Mailing List , Xen-devel , Andrew Morton , Dan Arai , Anne Holler , Pratap Subrahmanyam , Christopher Li , Joshua LeVasseur , Chris Wright , Rik Van Riel , Jyothy Reddy , Jack Lo , Kip Macy , Jan Beulich , Ky Srinivasan , Wim Coekaerts , Leendert van Doorn Subject: Re: [RFC, PATCH 24/24] i386 Vmi no idle hz References: <200603131817.k2DIHkMa005792@zach-dev.vmware.com> <20060315233128.GD1919@elf.ucw.cz> In-Reply-To: <20060315233128.GD1919@elf.ucw.cz> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 15 Mar 2006 23:59:32.0762 (UTC) FILETIME=[813E8FA0:01C6488C] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1864 Lines: 43 Pavel Machek wrote: > Hi! > >> When a VCPU enters its idle loop, it disables its periodic >> alarm and sets up a one shot alarm for the next time event. >> That way, it does not become ready to run just to service >> the periodic alarm interrupt. Instead, it can remain halted >> until there is some real work pending for it. This allows >> the hypervisor to use the physical resources more >> effectively since idle VCPUs will have lower overhead. > > Does this NO_IDLE_HZ work only on VMI-enabled runs or globally? We are > trying to get NO_IDLE_HZ working to save some power on notebooks; how > is it related to this? > The NO_IDLE_HZ implementation provided here is enabled when the VMI-Timer device is used as the timer interrupt source. The VMI-Timer device is only present on paravirtual hardware. However, the hooks introduced into the kernel (stop_hz_timer, restart_hz_timer) with these patches will be approximately the same (perhaps a subset) for implementing NO_IDLE_HZ on systems that use other interrupt sources. > Can you use NO_IDLE_HZ patches that are already floating around? > Certainly we plan to merge our NO_IDLE_HZ implementation with those patches once they are stabilized in the kernel. Presently, they seem to be too fast of a moving target to be worth merging at this point, though. Additionally, the VMI-Timer NO_IDLE_HZ implementation does not need all the machinery provided with the NO_IDLE_HZ patches that are floating around because the VMI-Timer code does not track time by counting interrupts. This leads to a fairly simplistic NO_IDLE_HZ implementation. Dan - 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/