From nobody Mon Feb 9 16:17:38 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 75CD0EB64DC for ; Sat, 15 Jul 2023 03:31:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230070AbjGODbx (ORCPT ); Fri, 14 Jul 2023 23:31:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229953AbjGODbh (ORCPT ); Fri, 14 Jul 2023 23:31:37 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73A893A9C; Fri, 14 Jul 2023 20:31:35 -0700 (PDT) Received: from kwepemm600003.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4R2v2672BwztRBW; Sat, 15 Jul 2023 11:28:30 +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, 15 Jul 2023 11:31:32 +0800 From: Yang Jihong To: , , , , , , , , , , , , , , , CC: Subject: [PATCH v2 4/7] perf record: Track sideband events for all CPUs when tracing selected CPUs Date: Sat, 15 Jul 2023 03:29:12 +0000 Message-ID: <20230715032915.97146-5-yangjihong1@huawei.com> X-Mailer: git-send-email 2.30.GIT In-Reply-To: <20230715032915.97146-1-yangjihong1@huawei.com> References: <20230715032915.97146-1-yangjihong1@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.67.174.95] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) 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 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 =3D 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 =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 | 7 ++++++- 2 files changed, 9 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 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 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. + */ + evsel =3D evlist__findnew_tracking_event(evlist, !!opts->target.cpu_list= ); if (!evsel) return -ENOMEM; =20 --=20 2.30.GIT