From nobody Mon Feb 9 16:16:44 2026 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 0CC63C001DE for ; Sat, 22 Jul 2023 09:35:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230097AbjGVJfQ (ORCPT ); Sat, 22 Jul 2023 05:35:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56364 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229805AbjGVJes (ORCPT ); Sat, 22 Jul 2023 05:34:48 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B38F430EF; Sat, 22 Jul 2023 02:34:46 -0700 (PDT) Received: from kwepemm600003.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4R7LpW34g8zrRjF; Sat, 22 Jul 2023 17:33:55 +0800 (CST) Received: from localhost.localdomain (10.67.174.95) 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; Sat, 22 Jul 2023 17:34:43 +0800 From: Yang Jihong To: , , , , , , , , , , , , , , , CC: Subject: [PATCH v3 4/7] perf record: Track sideband events for all CPUs when tracing selected CPUs Date: Sat, 22 Jul 2023 09:32:16 +0000 Message-ID: <20230722093219.174898-5-yangjihong1@huawei.com> X-Mailer: git-send-email 2.30.GIT In-Reply-To: <20230722093219.174898-1-yangjihong1@huawei.com> References: <20230722093219.174898-1-yangjihong1@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.67.174.95] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) 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 Content-Type: text/plain; charset="utf-8" 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=3D3 record -e cpu-clock -C 1 true Opening: cpu-clock ------------------------------------------------------------ perf_event_attr: type 1 (PERF_TYPE_SOFTWARE) size 136 config 0 (PERF_COUNT_SW_CPU_CLOCK) { sample_period, sample_freq } 4000 sample_type IP|TID|TIME|CPU|PERIOD|IDENTIFIER 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 =3D 5 Opening: dummy:u ------------------------------------------------------------ perf_event_attr: type 1 (PERF_TYPE_SOFTWARE) size 136 config 0x9 (PERF_COUNT_SW_DUMMY) { 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 =3D 6 sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 =3D 7 sys_perf_event_open: pid -1 cpu 2 group_fd -1 flags 0x8 =3D 9 sys_perf_event_open: pid -1 cpu 3 group_fd -1 flags 0x8 =3D 10 sys_perf_event_open: pid -1 cpu 4 group_fd -1 flags 0x8 =3D 11 sys_perf_event_open: pid -1 cpu 5 group_fd -1 flags 0x8 =3D 12 sys_perf_event_open: pid -1 cpu 6 group_fd -1 flags 0x8 =3D 13 sys_perf_event_open: pid -1 cpu 7 group_fd -1 flags 0x8 =3D 14 Signed-off-by: Yang Jihong --- tools/perf/Documentation/perf-record.txt | 3 +++ tools/perf/builtin-record.c | 14 +++++++++++++- 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Document= ation/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 capture= d only when the thread executes on the designated CPUs. Default is to monitor all CPUs. =20 +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 3ff9d972225e..4e8e97928f05 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -912,6 +912,7 @@ static int record__config_tracking_events(struct record= *rec) { struct record_opts *opts =3D &rec->opts; struct evlist *evlist =3D rec->evlist; + bool system_wide =3D false; struct evsel *evsel; =20 /* @@ -921,7 +922,18 @@ static int record__config_tracking_events(struct recor= d *rec) */ if (opts->target.initial_delay || target__has_cpu(&opts->target) || perf_pmus__num_core_pmus() > 1) { - evsel =3D 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. + * + * If all (non-dummy) evsel have exclude_user, + * system_wide is not needed. + */ + if (!!opts->target.cpu_list && !opts->all_kernel) + system_wide =3D true; + + evsel =3D evlist__findnew_tracking_event(evlist, system_wide); if (!evsel) return -ENOMEM; =20 --=20 2.30.GIT