From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759267AbdEVMDi (ORCPT ); Mon, 22 May 2017 08:03:38 -0400 Received: from merlin.infradead.org ([205.233.59.134]:47648 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932919AbdEVMDd (ORCPT ); Mon, 22 May 2017 08:03:33 -0400 Date: Mon, 22 May 2017 14:03:21 +0200 From: Peter Zijlstra To: kan.liang@intel.com Cc: mingo@redhat.com, eranian@google.com, linux-kernel@vger.kernel.org, alexander.shishkin@linux.intel.com, acme@redhat.com, jolsa@redhat.com, torvalds@linux-foundation.org, tglx@linutronix.de, vincent.weaver@maine.edu, ak@linux.intel.com Subject: Re: [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86 Message-ID: <20170522120321.e3b7my5lsjue6jpb@hirez.programming.kicks-ass.net> References: <1495213582-3635-1-git-send-email-kan.liang@intel.com> <1495213582-3635-2-git-send-email-kan.liang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1495213582-3635-2-git-send-email-kan.liang@intel.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 19, 2017 at 10:06:22AM -0700, kan.liang@intel.com wrote: > This patch was once merged, but reverted later. > Because ref-cycles can not be used anymore when watchdog is enabled. > The commit is 44530d588e142a96cf0cd345a7cb8911c4f88720 > > The patch 1/2 has extended the ref-cycles to GP counter. The concern > should be gone. So its not a problem if every Atom prior to Goldmont, and all Core/Core2 products regress? P6 and P4 you've entirely broken, as they don't have REF_CPU_CYCLES at all. So no, I don't think this is right even now.