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=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,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 8AE23ECDE46 for ; Fri, 26 Oct 2018 19:12:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4384C20868 for ; Fri, 26 Oct 2018 19:12:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="T/w3TUDB" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4384C20868 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 S1727672AbeJ0Dut (ORCPT ); Fri, 26 Oct 2018 23:50:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:34786 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726243AbeJ0Dut (ORCPT ); Fri, 26 Oct 2018 23:50:49 -0400 Received: from jouet.infradead.org (unknown [179.97.41.186]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B7F902082D; Fri, 26 Oct 2018 19:12:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1540581154; bh=s0oSt6wXNf4LHgSIk4QfcybCjFGwWKgUGV2PtUzciNY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=T/w3TUDB8sAqTdBN3LUR/+i6vtOc9SwsKB6pFvh5p4F8RELeZKPa+YVndL24Wv/04 xzG7L0DNl9T1s6PClfR0ERPa22DAtvaiA+vjQw2i5oYFtFQcZtwUoRh40Eb866YkG2 55YZ8sCXh6W5FgenpzCdc2X2eCiWtOEHquuP3HtI= Received: by jouet.infradead.org (Postfix, from userid 1000) id 5C627142C5F; Fri, 26 Oct 2018 16:12:31 -0300 (-03) Date: Fri, 26 Oct 2018 16:12:31 -0300 From: Arnaldo Carvalho de Melo To: "Liang, Kan" Cc: David Miller , linux-kernel@vger.kernel.org, Wang Nan , Jiri Olsa , Namhyung Kim , Kan Liang , Andi Kleen , Jin Yao , Peter Zijlstra Subject: Re: A concern about overflow ring buffer mode Message-ID: <20181026191231.GG3353@kernel.org> References: <20181026.104513.2239058788450235574.davem@davemloft.net> <20181026183805.GD3353@kernel.org> <20181026184255.GE3353@kernel.org> <20181026190211.GF3353@kernel.org> <3b81c999-9039-94e9-7a74-cdbd48fca08b@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3b81c999-9039-94e9-7a74-cdbd48fca08b@linux.intel.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Fri, Oct 26, 2018 at 03:07:40PM -0400, Liang, Kan escreveu: > 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) > { I see, it will disable that opts->overwrite if it finds the no-overwrite in the per-event definition, so the equivalent of the option I added below: perf top --no-overwrite is: perf top -e cycles/no-overwrite/ I checked and both have the same result. But I still think there is value in having the shorter form, ok? - Arnaldo > 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"), > >