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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 4D07BECDE46 for ; Fri, 26 Oct 2018 19:07:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 09B892054F for ; Fri, 26 Oct 2018 19:07:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 09B892054F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.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 S1727450AbeJ0Dp6 (ORCPT ); Fri, 26 Oct 2018 23:45:58 -0400 Received: from mga07.intel.com ([134.134.136.100]:44850 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726243AbeJ0Dp6 (ORCPT ); Fri, 26 Oct 2018 23:45:58 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Oct 2018 12:07:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,429,1534834800"; d="scan'208";a="84759486" Received: from linux.intel.com ([10.54.29.200]) by orsmga008.jf.intel.com with ESMTP; 26 Oct 2018 12:07:44 -0700 Received: from [10.252.142.77] (kliang2-mobl1.ccr.corp.intel.com [10.252.142.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by linux.intel.com (Postfix) with ESMTPS id 4B431580496; Fri, 26 Oct 2018 12:07:43 -0700 (PDT) Subject: Re: A concern about overflow ring buffer mode To: Arnaldo Carvalho de Melo , David Miller Cc: linux-kernel@vger.kernel.org, Wang Nan , Jiri Olsa , Namhyung Kim , Kan Liang , Andi Kleen , Jin Yao , Peter Zijlstra References: <20181026.104513.2239058788450235574.davem@davemloft.net> <20181026183805.GD3353@kernel.org> <20181026184255.GE3353@kernel.org> <20181026190211.GF3353@kernel.org> From: "Liang, Kan" Message-ID: <3b81c999-9039-94e9-7a74-cdbd48fca08b@linux.intel.com> Date: Fri, 26 Oct 2018 15:07:40 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181026190211.GF3353@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/26/2018 3:02 PM, Arnaldo Carvalho de Melo wrote: > So, I'm adding the following to my tree to help in diagnosing problems > with this overwrite mode: > Actually, you can use per-event overwrite term to disable overwrite mode for perf top. /* * Check per-event overwrite term. * perf top should support consistent term for all events. * - All events don't have per-event term * E.g. "cpu/cpu-cycles/,cpu/instructions/" * Nothing change, return 0. * - All events have same per-event term * E.g. "cpu/cpu-cycles,no-overwrite/,cpu/instructions,no-overwrite/ * Using the per-event setting to replace the opts->overwrite if * they are different, then return 0. * - Events have different per-event term * E.g. "cpu/cpu-cycles,overwrite/,cpu/instructions,no-overwrite/" * Return -1 * - Some of the event set per-event term, but some not. * E.g. "cpu/cpu-cycles/,cpu/instructions,no-overwrite/" * Return -1 */ static int perf_top__overwrite_check(struct perf_top *top) { Thanks, Kan > > From 40feb09001c7cc2ba8aeaa0a8f03b6d28fa4ca95 Mon Sep 17 00:00:00 2001 > From: Arnaldo Carvalho de Melo > Date: Fri, 26 Oct 2018 15:55:23 -0300 > Subject: [PATCH 1/1] perf top: Allow disabling the overwrite mode > > In ebebbf082357 ("perf top: Switch default mode to overwrite mode") we > forgot to leave a way to disable that new default, add a --overwrite > option that can be disabled using --no-overwrite, since the code already > in such a way that we can readily disable this mode. > > This is useful when investigating bugs with this mode like the recent > report from David Miller where lots of unknown symbols appear due to > disabling the events while processing them which disables all record > types, not just PERF_RECORD_SAMPLE, which makes it impossible to resolve > maps when we lose PERF_RECORD_MMAP records. > > This can be easily seen while building a kernel, when there are lots of > short lived processes. > > Cc: Adrian Hunter > Cc: Andi Kleen > Cc: David Ahern > Cc: David Miller > Cc: Jin Yao > Cc: Jiri Olsa > Cc: Kan Liang > Cc: Namhyung Kim > Cc: Peter Zijlstra > Cc: Wang Nan > Link: https://lkml.kernel.org/n/tip-oqgsz2bq4kgrnnajrafcdhie@git.kernel.org > Signed-off-by: Arnaldo Carvalho de Melo > --- > tools/perf/Documentation/perf-top.txt | 5 +++++ > tools/perf/builtin-top.c | 2 ++ > 2 files changed, 7 insertions(+) > > diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt > index 114fda12aa49..d4be6061fe1c 100644 > --- a/tools/perf/Documentation/perf-top.txt > +++ b/tools/perf/Documentation/perf-top.txt > @@ -242,6 +242,11 @@ Default is to monitor all CPUS. > --hierarchy:: > Enable hierarchy output. > > +--overwrite:: > + This is the default, but for investigating problems with it or any other strange > + behaviour like lots of unknown samples, we may want to disable this mode by using > + --no-overwrite. > + > --force:: > Don't do ownership validation. > > diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c > index d21d8751e749..214fad747b04 100644 > --- a/tools/perf/builtin-top.c > +++ b/tools/perf/builtin-top.c > @@ -1372,6 +1372,8 @@ int cmd_top(int argc, const char **argv) > "Show raw trace event output (do not use print fmt or plugins)"), > OPT_BOOLEAN(0, "hierarchy", &symbol_conf.report_hierarchy, > "Show entries in a hierarchy"), > + OPT_BOOLEAN(0, "overwrite", &top.record_opts.overwrite, > + "Use a backward ring buffer, default: yes"), > OPT_BOOLEAN(0, "force", &symbol_conf.force, "don't complain, do it"), > OPT_UINTEGER(0, "num-thread-synthesize", &top.nr_threads_synthesize, > "number of thread to run event synthesize"), >