From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH] x86 idle: repair large-server 50-watt idle-power regression Date: Thu, 19 Dec 2013 18:50:37 +0100 Message-ID: <20131219175037.GK2480@laptop.programming.kicks-ass.net> References: <20131219122257.GC11279@gmail.com> <52B316FF.50906@zytor.com> <20131219160210.GA28426@gmail.com> <52B31B21.6010901@zytor.com> <20131219162136.GM16438@laptop.programming.kicks-ass.net> <52B323BE.7090108@zytor.com> <20131219170741.GB30382@gmail.com> <20131219172535.GN16438@laptop.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from merlin.infradead.org ([205.233.59.134]:60596 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753650Ab3LSRut (ORCPT ); Thu, 19 Dec 2013 12:50:49 -0500 Content-Disposition: inline In-Reply-To: <20131219172535.GN16438@laptop.programming.kicks-ass.net> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Ingo Molnar Cc: "H. Peter Anvin" , Len Brown , x86@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Len Brown , stable@vger.kernel.org, Linus Torvalds , Thomas Gleixner , Mike Galbraith , Borislav Petkov On Thu, Dec 19, 2013 at 06:25:35PM +0100, Peter Zijlstra wrote: > On Thu, Dec 19, 2013 at 06:07:41PM +0100, Ingo Molnar wrote: > > Likewise, having a barrier before the MONITOR looks sensible as well. > > I again have to disagree, one would expect monitor to flush all that is > required to start the monitor -- and it actually does so. As is > testified by this extra CLFLUSH being called a bug workaround. SDM states that MONITOR is ordered like a LOAD, and a LOAD cannot pass a previous STORE to the same address. That said; there's enough holes in there to swim a titanic through, seeing how MONITOR stares at an entire cacheline and LOAD/STORE order is specified on location, whatever that means.