From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8BE2C43144 for ; Sat, 23 Jun 2018 18:48:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6B8E124CCB for ; Sat, 23 Jun 2018 18:48:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6B8E124CCB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751892AbeFWSs2 (ORCPT ); Sat, 23 Jun 2018 14:48:28 -0400 Received: from mga11.intel.com ([192.55.52.93]:13275 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751804AbeFWSs1 (ORCPT ); Sat, 23 Jun 2018 14:48:27 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Jun 2018 11:48:27 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,262,1526367600"; d="scan'208";a="59635053" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by FMSMGA003.fm.intel.com with ESMTP; 23 Jun 2018 11:48:27 -0700 Date: Sat, 23 Jun 2018 11:47:55 -0700 From: Fenghua Yu To: Peter Zijlstra Cc: Fenghua Yu , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Ashok Raj , Dave Hansen , Rafael Wysocki , Tony Luck , Alan Cox , Ravi V Shankar , Arjan van de Ven , linux-kernel , x86 Subject: Re: [RFC PATCH 00/16] x86/split_lock: Enable #AC exception for split locked accesses Message-ID: <20180623184755.GH18979@romley-ivt3.sc.intel.com> References: <1527435965-202085-1-git-send-email-fenghua.yu@intel.com> <20180621193738.GA13636@worktop.programming.kicks-ass.net> <20180621201851.GC114883@romley-ivt3.sc.intel.com> <20180621220003.GD114883@romley-ivt3.sc.intel.com> <20180621221337.GE2494@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180621221337.GE2494@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 22, 2018 at 12:13:37AM +0200, Peter Zijlstra wrote: > On Thu, Jun 21, 2018 at 03:00:03PM -0700, Fenghua Yu wrote: > > For example, on a consolidated real-time machine, some cores are running > > > Another example, in a public cloud deployed in the field, a user process > > In either case a single split-lock shouldn't be a real problem, if you > program the event with a count of 1 and have the NMI handler kill the > offending task, you should be good. > > Not saying the #AC isn't nicer, just saying the PMU based thing can > still work. The difference between perf event and #AC for split lock is perf event is after the fact while #AC is before the fact. In the examples (esp. the first example), hard real time cannot afforrd a split lock/bus lock. Perf captures the event and kill the task; but the split lock has been issued and harm has been done. #AC for split lock kills the task before the task generates split lock or bus lock to hurt real time tasks. Thanks. -Fenghua