From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: acpi_idle: Very idle Core i7 machine never enters C3 Date: Tue, 26 Jan 2010 22:45:20 +0100 Message-ID: <87y6jkee1b.fsf@basil.nowhere.org> References: <20100126084740.GA5265@jgarrett.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from one.firstfloor.org ([213.235.205.2]:56826 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754546Ab0AZVpW (ORCPT ); Tue, 26 Jan 2010 16:45:22 -0500 In-Reply-To: <20100126084740.GA5265@jgarrett.org> (Jeff Garrett's message of "Tue, 26 Jan 2010 02:47:40 -0600") Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Jeff Garrett Cc: linux-kernel@vger.kernel.org, Len Brown , linux-acpi@vger.kernel.org jeff@jgarrett.org (Jeff Garrett) writes: > Hi, > > I was trying to chase down a theory that my desktop machine (a core i7) > is running warm (the fan sounds like it's at full speed all the time, > and I think it's not always acted this way -- hence the theory). > > powertop is never showing it spending any time in C3... > > I compiled a kernel without USB/sound/radeon, and ran without X. I was > able to get the wakeups/sec down below 20, but no time is spent in C3. [...] > This may be a complete red herring, but I added some printk logic to > acpi_idle_bm_check(), and it is getting called often, but bm_status is > always 1. [I infer from this that the idle logic is trying to go into > C3, but this check is stopping it... Unless I misread something.] Normally a Core i7 (or any modern Intel systems) should not use bm_check at all. That's only for older systems that didn't support MWAIT with c-state hint, but relied on the old port based interface. So something is already confused there. I think it should still work though. Of course if you really have a lot of bus mastering in the background then yes there will be no C3. -Andi -- ak@linux.intel.com -- Speaking for myself only.