Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967045AbbLPVVL (ORCPT ); Wed, 16 Dec 2015 16:21:11 -0500 Received: from one.firstfloor.org ([193.170.194.197]:47728 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966873AbbLPVVG (ORCPT ); Wed, 16 Dec 2015 16:21:06 -0500 Date: Wed, 16 Dec 2015 22:21:04 +0100 From: Andi Kleen To: Stephane Eranian Cc: Andi Kleen , Arnaldo Carvalho de Melo , Peter Zijlstra , Jiri Olsa , Ingo Molnar , LKML , Namhyung Kim , Andi Kleen Subject: Re: [PATCH 05/10] perf, tools, stat: Basic support for TopDown in perf stat Message-ID: <20151216212104.GZ15533@two.firstfloor.org> References: <1450227266-2501-1-git-send-email-andi@firstfloor.org> <1450227266-2501-6-git-send-email-andi@firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2251 Lines: 66 > > +/* > > + * Check whether we can use a group for top down. > > + * Without a group may get bad results due to multiplexing. > > + */ > > That is not because you have a counter used by the NMI that > you cannot group. If HT is off you have plenty of counters to > do this. Such a heuristic wouldn't work on Atom where there are no more counters in this case. > > +static bool check_group(bool *warn) > > +{ > > + int n; > > + > > + if (sysctl__read_int("kernel/nmi_watchdog", &n) < 0) > > + return false; > > + if (n > 0) { > > + *warn = true; > > + return false; > > + } > > + return true; > > +} > > + > > I do not like this part very much. You are pulling in x86 specific > knowledge into > builtin_stat.c. Why not move this into an x86 specific file? Done. > > err = parse_events(evsel_list, transaction_attrs, NULL); > > @@ -1511,6 +1579,36 @@ static int add_default_attributes(void) > > return 0; > > } > > > > + if (topdown_run) { > > + char *str = NULL; > > + bool warn = false; > > + > > + filter_events(topdown_attrs, &str, check_group(&warn)); > > + if (topdown_attrs[0] && str) { > > + if (warn) > > + fprintf(stderr, > > + "nmi_watchdog enabled with topdown. May give wrong results.\n" > > + "Disable with echo 0 > /proc/sys/kernel/nmi_watchdog\n"); > > This is x86 specific. Why not just try it out and in case of error > suggest checking > if pinned system-wide events exist (such as NMI watchdog on x86). that would > be more generic. That's really complicated, i would have to tear down all state and then resubmit all the events. I think just checking the NMI watchdog is good enough. I couldn't give a sensible error message for the generic case anyways. -Andi -- ak@linux.intel.com -- Speaking for myself only. -- 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/