From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ciao.gmane.org (main.gmane.org [80.91.229.2]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 37CE4DE01A for ; Tue, 1 Apr 2008 06:05:10 +1000 (EST) Received: from list by ciao.gmane.org with local (Exim 4.43) id 1JgPcP-0002B8-Ml for linuxppc-dev@ozlabs.org; Mon, 31 Mar 2008 19:24:33 +0000 Received: from bi01p1.co.us.ibm.com ([32.97.110.142]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 31 Mar 2008 19:24:33 +0000 Received: from hollisb by bi01p1.co.us.ibm.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 31 Mar 2008 19:24:33 +0000 To: linuxppc-dev@ozlabs.org From: Hollis Blanchard Subject: Re: [PATCH] Add idle power save for ppc 4xx Date: Mon, 31 Mar 2008 19:24:24 +0000 (UTC) Message-ID: References: <10aea37177130bbe5de7.1206969157@thinkpadL> <1206983237.12155.60.camel@vader.jdub.homelinux.org> <20080331130518.2a6b0264@zod.rchland.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: news List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 31 Mar 2008 13:05:18 -0500, Josh Boyer wrote: > On Mon, 31 Mar 2008 12:07:17 -0500 > Josh Boyer wrote: > >> On Mon, 2008-03-31 at 08:12 -0500, Jerone Young wrote: >> > # HG changeset patch >> > # User Jerone Young # Date 1206969060 18000 >> > # Node ID 10aea37177130bbe5de7bee6ec06d9010bc5da1f # Parent >> > 1506aa38ddabb0bf73fff3ac3f3db5f9ef6458cc Add idle power save for ppc >> > 4xx >> > >> > This patch sets the wait state MSR when power_save is called in >> > cpu_idle loop for ppc4xx. This is mainly to help out virtualization >> > solutions such as KVM. This way the virtualization soultions are able >> > to tell if the guest kernel is idle. >> > >> > I have tested this on hardware & KVM virtual guest. >> >> I'm not overly thrilled with adding this to all of 4xx. It doesn't >> actually save much power at all (1% on a project that actually measured >> it with an amp meter recently) and there's really no other benefit to >> doing it outside of the virtual guest case. So it slightly helps hardware, and it helps virtualization a *lot*. What's the problem? >> I'm assuming you pass a dtb to the virtual guest when you start it up. >> Could you define a property in the CPU node there that can be parsed to >> use the power_save function instead of always making it the default? > > Actually, you probably don't want this as a property in the device tree. > It doesn't describe hardware. A Kconfig option might be warranted > though. There will be a device tree binding for hypervisor properties, so if it's not always enabled, having a hypervisor node (for any hypervisor) in the device tree would be an indicator. Far better than a Kconfig option, at any rate. -- Hollis Blanchard IBM Linux Technology Center