From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752897AbbJSHIR (ORCPT ); Mon, 19 Oct 2015 03:08:17 -0400 Received: from mail-wi0-f178.google.com ([209.85.212.178]:36528 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750799AbbJSHIQ (ORCPT ); Mon, 19 Oct 2015 03:08:16 -0400 Date: Mon, 19 Oct 2015 09:08:12 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: Andi Kleen , Andi Kleen , linux-kernel@vger.kernel.org, Thomas Gleixner , Mike Galbraith Subject: Re: [PATCH 1/4] x86, perf: Use a new PMU ack sequence on Skylake Message-ID: <20151019070812.GB17855@gmail.com> References: <1444952280-24184-1-git-send-email-andi@firstfloor.org> <1444952280-24184-2-git-send-email-andi@firstfloor.org> <20151016115107.GV3816@twins.programming.kicks-ass.net> <20151016133514.GB15102@tassilo.jf.intel.com> <20151016150035.GY3816@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151016150035.GY3816@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > On Fri, Oct 16, 2015 at 06:35:14AM -0700, Andi Kleen wrote: > > > > In principle the sequence should work on other CPUs too, but > > > > since I only tested on Skylake it is only enabled there. > > > > > > I would very much like a reduction of the ack states. You introduced the > > > late thing, which should also work for everyone, and now you introduce yet > > > another variant. > > > > Ingo suggested to do it this way. Originally I thought it wasn't needed, but I > > think now that late-ack made some of the races that eventually caused Skylake > > LBR to fall over worse. So in hindsight it was a good idea to not use it > > everywhere. > > > > > I would very much prefer a single ack scheme if at all possible. > > > > Could enable it everywhere, but then users would need to test it on most types > > of CPUs, as I can't. > > I think Mike still has a Core2 machine (and I might be able to dig out a > laptop), Ingo should have a NHM(-EP), I have SNB, IVB-EP, HSW. So if you could > test at least BDW and SKL we might have decent test coverage. > > Ingo, do you want to first merge the safe patch and then clean up? Yeah, would be nice to structure it that way, out of general paranoia. Thanks, Ingo