From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932273AbbJPPAr (ORCPT ); Fri, 16 Oct 2015 11:00:47 -0400 Received: from casper.infradead.org ([85.118.1.10]:33947 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932123AbbJPPAi (ORCPT ); Fri, 16 Oct 2015 11:00:38 -0400 Date: Fri, 16 Oct 2015 17:00:35 +0200 From: Peter Zijlstra To: Andi Kleen Cc: Andi Kleen , linux-kernel@vger.kernel.org, Ingo Molnar , Thomas Gleixner , Mike Galbraith Subject: Re: [PATCH 1/4] x86, perf: Use a new PMU ack sequence on Skylake Message-ID: <20151016150035.GY3816@twins.programming.kicks-ass.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151016133514.GB15102@tassilo.jf.intel.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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?