From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: 50 Watt idle power regression bisected to Linux-3.10 Date: Thu, 12 Dec 2013 07:06:57 -0800 Message-ID: <52A9D111.3090409@zytor.com> References: <20131211113839.GF21683@pd.tnic> <20131211115239.GA21999@twins.programming.kicks-ass.net> <1386764955.12005.60.camel@marge.simpson.net> <20131211124352.GB21999@twins.programming.kicks-ass.net> <20131211134048.GH21683@pd.tnic> <20131211145655.GB4510@gmail.com> <20131211164318.GA2480@laptop.programming.kicks-ass.net> <20131211175036.GC12431@gmail.com> <52A8F073.9040500@zytor.com> <20131212085143.GC21999@twins.programming.kicks-ass.net> <20131212132846.GA16750@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from terminus.zytor.com ([198.137.202.10]:48812 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751522Ab3LLPH7 (ORCPT ); Thu, 12 Dec 2013 10:07:59 -0500 In-Reply-To: <20131212132846.GA16750@gmail.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Ingo Molnar , Peter Zijlstra Cc: Borislav Petkov , Mike Galbraith , Thomas Gleixner , Len Brown , Linux PM list , "linux-kernel@vger.kernel.org" , Jeremy Eder , x86@kernel.org On 12/12/2013 05:28 AM, Ingo Molnar wrote: >> >> The reason we use thread_info::flags is because we need to write >> TIF_NEED_RESCHED into it to wake up anyhow. >> >> Using another cacheline would mean the wakeup path would need to write a >> second cross cpu cacheline -- that is badness too. >> >> So no, I don't think we want to listen to another line. > Right, okay, so that's the implicit wakeup. However, I would think the CLFLUSH would hurt a lot more. -hpa