From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Galbraith Subject: Re: 50 Watt idle power regression bisected to Linux-3.10 Date: Sun, 08 Dec 2013 05:57:04 +0100 Message-ID: <1386478624.4748.19.camel@marge.simpson.net> References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from moutng.kundenserver.de ([212.227.17.8]:57705 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754171Ab3LHE5L (ORCPT ); Sat, 7 Dec 2013 23:57:11 -0500 In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Len Brown Cc: tglx@linutronix.de, Peter Zijlstra , Linux PM list , "linux-kernel@vger.kernel.org" , Jeremy Eder , x86@kernel.org On Sat, 2013-12-07 at 03:00 -0500, Len Brown wrote: > Hello Thomas, > > An idle WSM-EX box (40 Xeon cores) runs 50 Watts hotter after this patch: > > commit 7d1a941731fabf27e5fb6edbebb79fe856edb4e5 > Author: Thomas Gleixner > Date: Thu Mar 21 22:50:03 2013 +0100 > > x86: Use generic idle loop > > ie. the commit before this patch (aba92c9e2cf3042bf6efc68fa2e4235ba01bf499) > runs at 50 watts less, as do Linux 3.7, 3.8 and 3.9. > > The difference is that the good kernels allow about 98% residence > in the package C6 state, while the bad kernel is so noisy that it > gets into pc6 0% of the time. > (indeed, even core C6 is reduced to about 50% from over 99%) FWIW, my little x3550 (E5620) box is spending ~99% of its time in C3 per powertop, deepest state it has. It took a big hit from 69a37bea as well as 7d1a9417, but with revert of 69a37bea, and addition of ea811747, it's fairly close to 3.7 in fastpath weight, and greenery _seems_ fine. -Mike