Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757132AbbEVNkw (ORCPT ); Fri, 22 May 2015 09:40:52 -0400 Received: from mail-ob0-f172.google.com ([209.85.214.172]:34270 "EHLO mail-ob0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756584AbbEVNku (ORCPT ); Fri, 22 May 2015 09:40:50 -0400 MIME-Version: 1.0 In-Reply-To: <20150522133636.GE3644@twins.programming.kicks-ass.net> References: <20150522112146.GZ3644@twins.programming.kicks-ass.net> <20150522112800.GO18673@twins.programming.kicks-ass.net> <20150522125344.GA3644@twins.programming.kicks-ass.net> <20150522125908.GB3644@twins.programming.kicks-ass.net> <20150522132534.GD3644@twins.programming.kicks-ass.net> <20150522133636.GE3644@twins.programming.kicks-ass.net> Date: Fri, 22 May 2015 06:40:49 -0700 Message-ID: Subject: Re: [PATCH 02/10] perf/x86: Improve HT workaround GP counter constraint From: Stephane Eranian To: Peter Zijlstra Cc: Ingo Molnar , Vince Weaver , Jiri Olsa , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1084 Lines: 23 On Fri, May 22, 2015 at 6:36 AM, Peter Zijlstra wrote: > On Fri, May 22, 2015 at 06:29:47AM -0700, Stephane Eranian wrote: >> On Fri, May 22, 2015 at 6:25 AM, Peter Zijlstra wrote: >> > On Fri, May 22, 2015 at 06:07:00AM -0700, Stephane Eranian wrote: >> >> >> >> One other thing I noticed is that the --n_excl needs to be protected by the >> >> excl_cntrs->lock in put_excl_constraints(). >> > >> > Nah, its strictly per cpu. >> >> No. the excl_cntrs struct is pointed to by cpuc but it is shared between the >> sibling HT. Otherwise this would not work! > > n_excl is per cpuc, see the trickery with has_exclusive vs > exclusive_present on how I avoid the lock. Yes, but I believe you create a store forward penalty with this. You store 16bits and you load 32 bits on the same cache line. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/