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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 9E101C2BA19 for ; Wed, 22 Apr 2020 00:53:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7A9F02071E for ; Wed, 22 Apr 2020 00:53:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726403AbgDVAxt (ORCPT ); Tue, 21 Apr 2020 20:53:49 -0400 Received: from mga09.intel.com ([134.134.136.24]:52610 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726296AbgDVAxs (ORCPT ); Tue, 21 Apr 2020 20:53:48 -0400 IronPort-SDR: 7dy2JvWpSVUnipmZirNjRuinsIr13PI5HXN9SZrWje7eOt5YbmvQwwVePIpBP+0k9B3BqZtHut 6wSgUruCwJHQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Apr 2020 17:53:47 -0700 IronPort-SDR: B5XHrYzTIV+K7fiT2gaOztkRTRE7Tzlbhu9HW0fYL9AjyaLmanclAIdADlWtQZYFuKd+jCMfUA UW3R121cLdJQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,412,1580803200"; d="scan'208";a="365519277" Received: from yjin15-mobl1.ccr.corp.intel.com (HELO [10.238.4.151]) ([10.238.4.151]) by fmsmga001.fm.intel.com with ESMTP; 21 Apr 2020 17:53:41 -0700 Subject: Re: [PATCH v2] perf stat: Improve runtime stat for interval mode To: Arnaldo Carvalho de Melo Cc: jolsa@kernel.org, peterz@infradead.org, mingo@redhat.com, alexander.shishkin@linux.intel.com, Linux-kernel@vger.kernel.org, ak@linux.intel.com, kan.liang@intel.com, yao.jin@intel.com References: <20200420145417.6864-1-yao.jin@linux.intel.com> <20200421135329.GA9110@kernel.org> From: "Jin, Yao" Message-ID: Date: Wed, 22 Apr 2020 08:53:41 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200421135329.GA9110@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 Hi Arnaldo, On 4/21/2020 9:53 PM, Arnaldo Carvalho de Melo wrote: > Em Mon, Apr 20, 2020 at 10:54:17PM +0800, Jin Yao escreveu: >> For interval mode, the metric is printed after # if it exists. But >> it's not calculated by the counts generated in this interval. See >> following examples, >> >> root@kbl-ppc:~# perf stat -M CPI -I1000 --interval-count 2 >> # time counts unit events >> 1.000422803 764,809 inst_retired.any # 2.9 CPI >> 1.000422803 2,234,932 cycles >> 2.001464585 1,960,061 inst_retired.any # 1.6 CPI >> 2.001464585 4,022,591 cycles >> >> The second CPI should not be 1.6 (4,022,591/1,960,061 is 2.1) >> >> root@kbl-ppc:~# perf stat -e cycles,instructions -I1000 --interval-count 2 >> # time counts unit events >> 1.000429493 2,869,311 cycles >> 1.000429493 816,875 instructions # 0.28 insn per cycle >> 2.001516426 9,260,973 cycles >> 2.001516426 5,250,634 instructions # 0.87 insn per cycle >> >> The second 'insn per cycle' should not be 0.87 (5,250,634/9,260,973 is 0.57). >> >> The current code uses a global variable rt_stat for tracking and >> updating the std dev of runtime stat. Unlike the counts, rt_stat is >> not reset for interval. While the counts are reset for interval. >> >> perf_stat_process_counter() >> { >> if (config->interval) >> init_stats(ps->res_stats); >> } >> >> So for interval, the rt_stat should be reset either. > > s/either/too/g right? > Yes, should use "too" here. :) > And please try and find what was the cset that introduced the problem, > so that we can have a Fixes: line and the stable series can pick it, ok? > > - Arnaldo > I have tried to find the patch which introduced this issue. 51fd2df1e882 ("perf stat: Fix interval output values"). This patch zeros stats for interval mode. I just think it should reset rt_stat too. But I really don't know if it's fair to this patch so I don't add it in my patch description. Thanks Jin Yao >> This patch resets rt_stat before read_counters, so the runtime >> stat is only calculated by the counts generated in this interval. >> >> With this patch, >> >> root@kbl-ppc:~# perf stat -M CPI -I1000 --interval-count 2 >> # time counts unit events >> 1.000420924 2,408,818 inst_retired.any # 2.1 CPI >> 1.000420924 5,010,111 cycles >> 2.001448579 2,798,407 inst_retired.any # 1.6 CPI >> 2.001448579 4,599,861 cycles >> >> root@kbl-ppc:~# perf stat -e cycles,instructions -I1000 --interval-count 2 >> # time counts unit events >> 1.000428555 2,769,714 cycles >> 1.000428555 774,462 instructions # 0.28 insn per cycle >> 2.001471562 3,595,904 cycles >> 2.001471562 1,243,703 instructions # 0.35 insn per cycle >> >> Now the second 'insn per cycle' and CPI are calculated by the counts >> generated in this interval. >> >> v2: >> --- >> Use just existing perf_stat__reset_shadow_per_stat(&rt_stat). >> We don't need to define new function perf_stat__reset_rt_stat. >> >> Signed-off-by: Jin Yao >> --- >> tools/perf/Documentation/perf-stat.txt | 2 ++ >> tools/perf/builtin-stat.c | 1 + >> 2 files changed, 3 insertions(+) >> >> diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt >> index 4d56586b2fb9..3fb5028aef08 100644 >> --- a/tools/perf/Documentation/perf-stat.txt >> +++ b/tools/perf/Documentation/perf-stat.txt >> @@ -176,6 +176,8 @@ Print count deltas every N milliseconds (minimum: 1ms) >> The overhead percentage could be high in some cases, for instance with small, sub 100ms intervals. Use with caution. >> example: 'perf stat -I 1000 -e cycles -a sleep 5' >> >> +If the metric exists, it is calculated by the counts generated in this interval and the metric is printed after #. >> + >> --interval-count times:: >> Print count deltas for fixed number of times. >> This option should be used together with "-I" option. >> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c >> index 9207b6c45475..3f050d85c277 100644 >> --- a/tools/perf/builtin-stat.c >> +++ b/tools/perf/builtin-stat.c >> @@ -359,6 +359,7 @@ static void process_interval(void) >> clock_gettime(CLOCK_MONOTONIC, &ts); >> diff_timespec(&rs, &ts, &ref_time); >> >> + perf_stat__reset_shadow_per_stat(&rt_stat); >> read_counters(&rs); >> >> if (STAT_RECORD) { >> -- >> 2.17.1 >> >