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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B914FEB64DD for ; Tue, 18 Jul 2023 09:07:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231302AbjGRJHe (ORCPT ); Tue, 18 Jul 2023 05:07:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49048 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229471AbjGRJHc (ORCPT ); Tue, 18 Jul 2023 05:07:32 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3954D2; Tue, 18 Jul 2023 02:07:30 -0700 (PDT) Received: from kwepemm600003.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4R4tLF2pjKztRXk; Tue, 18 Jul 2023 17:04:21 +0800 (CST) Received: from [10.67.111.205] (10.67.111.205) by kwepemm600003.china.huawei.com (7.193.23.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Tue, 18 Jul 2023 17:07:26 +0800 Subject: Re: [PATCH v2 4/7] perf record: Track sideband events for all CPUs when tracing selected CPUs To: Adrian Hunter , , , , , , , , , , , , , , , References: <20230715032915.97146-1-yangjihong1@huawei.com> <20230715032915.97146-5-yangjihong1@huawei.com> <8591416b-77aa-fc9d-fe39-21c718600592@intel.com> From: Yang Jihong Message-ID: Date: Tue, 18 Jul 2023 17:07:25 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <8591416b-77aa-fc9d-fe39-21c718600592@intel.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.111.205] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To kwepemm600003.china.huawei.com (7.193.23.202) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On 2023/7/17 22:25, Adrian Hunter wrote: > On 15/07/23 06:29, Yang Jihong wrote: >> User space tasks can migrate between CPUs, we need to track side-band >> events for all CPUs. >> >> The specific scenarios are as follows: >> >> CPU0 CPU1 >> perf record -C 0 start >> taskA starts to be created and executed >> -> PERF_RECORD_COMM and PERF_RECORD_MMAP >> events only deliver to CPU1 >> ...... >> | >> migrate to CPU0 >> | >> Running on CPU0 <----------/ >> ... >> >> perf record -C 0 stop >> >> Now perf samples the PC of taskA. However, perf does not record the >> PERF_RECORD_COMM and PERF_RECORD_MMAP events of taskA. >> Therefore, the comm and symbols of taskA cannot be parsed. >> >> The solution is to record sideband events for all CPUs when tracing >> selected CPUs. Because this modifies the default behavior, add related >> comments to the perf record man page. >> >> The sys_perf_event_open invoked is as follows: >> >> # perf --debug verbose=3 record -e cpu-clock -C 1 true >> >> Opening: cpu-clock >> ------------------------------------------------------------ >> perf_event_attr: >> type 1 >> size 136 >> { sample_period, sample_freq } 4000 >> sample_type IP|TID|TIME|ID|CPU|PERIOD >> read_format ID|LOST >> disabled 1 >> inherit 1 >> freq 1 >> sample_id_all 1 >> exclude_guest 1 >> ------------------------------------------------------------ >> sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 = 5 >> Opening: dummy:HG >> ------------------------------------------------------------ >> perf_event_attr: >> type 1 >> size 136 >> config 0x9 >> { sample_period, sample_freq } 1 >> sample_type IP|TID|TIME|CPU|IDENTIFIER >> read_format ID|LOST >> inherit 1 >> exclude_kernel 1 >> exclude_hv 1 >> mmap 1 >> comm 1 >> task 1 >> sample_id_all 1 >> exclude_guest 1 >> mmap2 1 >> comm_exec 1 >> ksymbol 1 >> bpf_event 1 >> ------------------------------------------------------------ >> sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 = 6 >> sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 = 7 >> sys_perf_event_open: pid -1 cpu 2 group_fd -1 flags 0x8 = 9 >> sys_perf_event_open: pid -1 cpu 3 group_fd -1 flags 0x8 = 10 >> sys_perf_event_open: pid -1 cpu 4 group_fd -1 flags 0x8 = 11 >> sys_perf_event_open: pid -1 cpu 5 group_fd -1 flags 0x8 = 12 >> sys_perf_event_open: pid -1 cpu 6 group_fd -1 flags 0x8 = 13 >> sys_perf_event_open: pid -1 cpu 7 group_fd -1 flags 0x8 = 14 >> >> >> Signed-off-by: Yang Jihong >> --- >> tools/perf/Documentation/perf-record.txt | 3 +++ >> tools/perf/builtin-record.c | 7 ++++++- >> 2 files changed, 9 insertions(+), 1 deletion(-) >> >> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt >> index 680396c56bd1..dac53ece51ab 100644 >> --- a/tools/perf/Documentation/perf-record.txt >> +++ b/tools/perf/Documentation/perf-record.txt >> @@ -388,6 +388,9 @@ comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0- >> In per-thread mode with inheritance mode on (default), samples are captured only when >> the thread executes on the designated CPUs. Default is to monitor all CPUs. >> >> +User space tasks can migrate between CPUs, so when tracing selected CPUs, >> +a dummy event is created to track sideband for all CPUs. >> + >> -B:: >> --no-buildid:: >> Do not save the build ids of binaries in the perf.data files. This skips >> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c >> index ccbcb005e188..4a15b2e06f45 100644 >> --- a/tools/perf/builtin-record.c >> +++ b/tools/perf/builtin-record.c >> @@ -921,7 +921,12 @@ static int record__config_tracking_events(struct record *rec) >> */ >> if (opts->target.initial_delay || target__has_cpu(&opts->target) || >> perf_pmus__num_core_pmus() > 1) { >> - evsel = evlist__findnew_tracking_event(evlist, false); >> + >> + /* >> + * User space tasks can migrate between CPUs, so when tracing >> + * selected CPUs, sideband for all CPUs is still needed. > > So if all (non-dummy) evsel have exclude_user, then system_wide is not needed. OK, The previous judgment system_wide is simplified and will be refined here. > >> + */ >> + evsel = evlist__findnew_tracking_event(evlist, !!opts->target.cpu_list); >> if (!evsel) >> return -ENOMEM; >> > > . >