From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0196A222572; Fri, 10 Jan 2025 19:26:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736537199; cv=none; b=SJDiGPMtjMCrkYJCerhzeLSh8PUSaYwM6TauxdLDUNM1QAbezh5wbjeI+uPp2ZWyT/xEpKCJ0fGL+W0PSWEyaABsWmGnP+Oc5mupeoOmArjafPebpYRjlcaOUkQzThwv7YUiv1XPi4+5gVsi/Q9ejR8SaogIY3CjKSN35ImYQR4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736537199; c=relaxed/simple; bh=nykxuUtW5cZb8mQZt95vsTUg17pjlFd01Ue3uzqjE+I=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Bu3eFImMKxLtk0abz1kF5hiHZTtrI5qPJ4gW0gF3HDX+kh1KfV210fqtkC/jiXHp4g7QnfQWikvWCeyhGf0tcio783IUDDGaSwEtYn4h1hohOhk4MxE0weOHMJ218Gu4s9YgKbKiktdiakzfOV1ZspQsgJULEXjy215DF5ToQi8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bdPkI3hx; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bdPkI3hx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E9693C4CEE7; Fri, 10 Jan 2025 19:26:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736537198; bh=nykxuUtW5cZb8mQZt95vsTUg17pjlFd01Ue3uzqjE+I=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bdPkI3hxggWc7OXwOL0tiDlQ51BOp3vLXgOcRojceLGLuXfTb5gb2po8ChN4SYJmK 9CIvhaX/w1DQVl8xdDTLbAVzEk8ej5ZpuhAi7Ej3wxdZbZVgtlmA5oElgF/h9tByy8 8xcpAQMXbG9dgfJE3zOCiQle3jX16Xqf1W9coy6+E4I0s/NiqJ/RgIP0VW14kjwOO+ c3CfcaEv4pXegJmYh/MLCt/Lm8nToAhShSWX7I4eSawLo4Jb4ZKhdrEp27GtAY9p6K Mkpy4U7hDiup6R1A8tMEtTAkQzeU3kfij7HoaNV/DjDfCVe4K0yndqQ0HFYH4k2fe9 6o5gdQdbQZ1qg== Date: Fri, 10 Jan 2025 11:26:36 -0800 From: Namhyung Kim To: Ian Rogers Cc: Arnaldo Carvalho de Melo , Linus Torvalds , Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Jiri Olsa , Adrian Hunter , Kan Liang , James Clark , Ze Gao , Weilin Wang , Dominique Martinet , Jean-Philippe Romain , Junhao He , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Aditya Bodkhe , Leo Yan , Atish Patra Subject: Re: [PATCH v5 3/4] perf record: Skip don't fail for events that don't open Message-ID: References: <20250109222109.567031-1-irogers@google.com> <20250109222109.567031-4-irogers@google.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Jan 10, 2025 at 08:42:02AM -0800, Ian Rogers wrote: > On Fri, Jan 10, 2025 at 6:18 AM Arnaldo Carvalho de Melo > wrote: > > > > Adding Linus to the CC list as he participated in this discussion in the > > past, so a heads up about changes in this area that are being further > > discussed. > > Linus blocks my email so I'm not sure of the point. That's unfortunate, but he should be able to see others' reply. > > > On Thu, Jan 09, 2025 at 05:25:03PM -0800, Namhyung Kim wrote: > > > On Thu, Jan 09, 2025 at 02:21:08PM -0800, Ian Rogers wrote: > > > > Whilst for many tools it is an expected behavior that failure to open > > > > a perf event is a failure, ARM decided to name PMU events the same as > > > > legacy events and then failed to rename such events on a server uncore > > > > SLC PMU. As perf's default behavior when no PMU is specified is to > > > > open the event on all PMUs that advertise/"have" the event, this > > > > yielded failures when trying to make the priority of legacy and > > > > sysfs/json events uniform - something requested by RISC-V and ARM. A > > > > legacy event user on ARM hardware may find their event opened on an > > > > uncore PMU which for perf record will fail. Arnaldo suggested skipping > > > > such events which this patch implements. Rather than have the skipping > > > > conditional on running on ARM, the skipping is done on all > > > > architectures as such a fundamental behavioral difference could lead > > > > to problems with tools built/depending on perf. > > > > > > > > An example of perf record failing to open events on x86 is: > > > > ``` > > > > $ perf record -e data_read,cycles,LLC-prefetch-read -a sleep 0.1 > > > > Error: > > > > Failure to open event 'data_read' on PMU 'uncore_imc_free_running_0' which will be removed. > > > > The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (data_read). > > > > "dmesg | grep -i perf" may provide additional information. > > > > > > > > Error: > > > > Failure to open event 'data_read' on PMU 'uncore_imc_free_running_1' which will be removed. > > > > The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (data_read). > > > > "dmesg | grep -i perf" may provide additional information. > > > > > > > > Error: > > > > Failure to open event 'LLC-prefetch-read' on PMU 'cpu' which will be removed. > > > > The LLC-prefetch-read event is not supported. > > > > [ perf record: Woken up 1 times to write data ] > > > > [ perf record: Captured and wrote 2.188 MB perf.data (87 samples) ] > > > > > > I'm afraid this can be too noisy. > > > > Agreed. > > > > > > $ perf report --stats > > > > Aggregated stats: > > > > TOTAL events: 17255 > > > > MMAP events: 284 ( 1.6%) > > > > COMM events: 1961 (11.4%) > > > > EXIT events: 1 ( 0.0%) > > > > FORK events: 1960 (11.4%) > > > > SAMPLE events: 87 ( 0.5%) > > > > MMAP2 events: 12836 (74.4%) > > > > KSYMBOL events: 83 ( 0.5%) > > > > BPF_EVENT events: 36 ( 0.2%) > > > > FINISHED_ROUND events: 2 ( 0.0%) > > > > ID_INDEX events: 1 ( 0.0%) > > > > THREAD_MAP events: 1 ( 0.0%) > > > > CPU_MAP events: 1 ( 0.0%) > > > > TIME_CONV events: 1 ( 0.0%) > > > > FINISHED_INIT events: 1 ( 0.0%) > > > > cycles stats: > > > > SAMPLE events: 87 > > > > ``` > > > > > > > > If all events fail to open then the perf record will fail: > > > > ``` > > > > $ perf record -e LLC-prefetch-read true > > > > Error: > > > > Failure to open event 'LLC-prefetch-read' on PMU 'cpu' which will be removed. > > > > The LLC-prefetch-read event is not supported. > > > > Error: > > > > Failure to open any events for recording > > > > ``` > > > > > > > > As an evlist may have dummy events that open when all command line > > > > events fail we ignore dummy events when detecting if at least some > > > > events open. This still permits the dummy event on its own to be used > > > > as a permission check: > > > > ``` > > > > $ perf record -e dummy true > > > > [ perf record: Woken up 1 times to write data ] > > > > [ perf record: Captured and wrote 0.046 MB perf.data ] > > > > ``` > > > > but allows failure when a dummy event is implicilty inserted or when > > > > there are insufficient permissions to open it: > > > > ``` > > > > $ perf record -e LLC-prefetch-read -a true > > > > Error: > > > > Failure to open event 'LLC-prefetch-read' on PMU 'cpu' which will be removed. > > > > The LLC-prefetch-read event is not supported. > > > > Error: > > > > Failure to open any events for recording > > > > ``` > > > > > > > > The issue with legacy events is that on RISC-V they want the driver to > > > > not have mappings from legacy to non-legacy config encodings for each > > > > vendor/model due to size, complexity and difficulty to update. It was > > > > reported that on ARM Apple-M? CPUs the legacy mapping in the driver > > > > was broken and the sysfs/json events should always take precedent, > > > > however, it isn't clear this is still the case. It is the case that > > > > without working around this issue a legacy event like cycles without a > > > > PMU can encode differently than when specified with a PMU - the > > > > non-PMU version favoring legacy encodings, the PMU one avoiding legacy > > > > encodings. > > > > > > > > The patch removes events and then adjusts the idx value for each > > > > evsel. This is done so that the dense xyarrays used for file > > > > descriptors, etc. don't contain broken entries. As event opening > > > > happens relatively late in the record process, use of the idx value > > > > before the open will have become corrupted, so it is expected there > > > > are latent bugs hidden behind this change - the change is best > > > > effort. As the only vendor that has broken event names is ARM, this > > > > will principally effect ARM users. They will also experience warning > > > > messages like those above because of the uncore PMU advertising legacy > > > > event names. > > > > > > > > Suggested-by: Arnaldo Carvalho de Melo > > > > Signed-off-by: Ian Rogers > > > > Tested-by: James Clark > > > > Tested-by: Leo Yan > > > > Tested-by: Atish Patra > > > > --- > > > > tools/perf/builtin-record.c | 47 ++++++++++++++++++++++++++++++++----- > > > > 1 file changed, 41 insertions(+), 6 deletions(-) > > > > > > > > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c > > > > index 5db1aedf48df..c0b8249a3787 100644 > > > > --- a/tools/perf/builtin-record.c > > > > +++ b/tools/perf/builtin-record.c > > > > @@ -961,7 +961,6 @@ 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) { > > > > - > > > > /* > > > > * User space tasks can migrate between CPUs, so when tracing > > > > * selected CPUs, sideband for all CPUs is still needed. > > > > @@ -1366,6 +1365,7 @@ static int record__open(struct record *rec) > > > > struct perf_session *session = rec->session; > > > > struct record_opts *opts = &rec->opts; > > > > int rc = 0; > > > > + bool skipped = false; > > > > > > > > evlist__for_each_entry(evlist, pos) { > > > > try_again: > > > > @@ -1381,15 +1381,50 @@ static int record__open(struct record *rec) > > > > pos = evlist__reset_weak_group(evlist, pos, true); > > > > goto try_again; > > > > } > > > > - rc = -errno; > > > > evsel__open_strerror(pos, &opts->target, errno, msg, sizeof(msg)); > > > > - ui__error("%s\n", msg); > > > > - goto out; > > > > + ui__error("Failure to open event '%s' on PMU '%s' which will be removed.\n%s\n", > > > > + evsel__name(pos), evsel__pmu_name(pos), msg); > > > > > How about changing it to pr_debug() and add below ... > > > > That sounds better. > > > > > > + pos->skippable = true; > > > > + skipped = true; > > > > + } else { > > > > + pos->supported = true; > > > > } > > > > - > > > > - pos->supported = true; > > > > } > > > > > > > > + if (skipped) { > > > > + struct evsel *tmp; > > > > + int idx = 0; > > > > + bool evlist_empty = true; > > > > + > > > > + /* Remove evsels that failed to open and update indices. */ > > > > + evlist__for_each_entry_safe(evlist, tmp, pos) { > > > > + if (pos->skippable) { > > > > + evlist__remove(evlist, pos); > > > > + continue; > > > > + } > > > > + > > > > + /* > > > > + * Note, dummy events may be command line parsed or > > > > + * added by the tool. We care about supporting `perf > > > > + * record -e dummy` which may be used as a permission > > > > + * check. Dummy events that are added to the command > > > > + * line and opened along with other events that fail, > > > > + * will still fail as if the dummy events were tool > > > > + * added events for the sake of code simplicity. > > > > + */ > > > > + if (!evsel__is_dummy_event(pos)) > > > > + evlist_empty = false; > > > > + } > > > > + evlist__for_each_entry(evlist, pos) { > > > > + pos->core.idx = idx++; > > > > + } > > > > + /* If list is empty then fail. */ > > > > + if (evlist_empty) { > > > > + ui__error("Failure to open any events for recording.\n"); > > > > + rc = -1; > > > > + goto out; > > > > + } > > > > > ... ? > > > > > if (!verbose) > > > ui__warning("Removed some unsupported events, use -v for details.\n"); > > > > And even this one would be best left for cases where we can determine > > that its a new situation, i.e. one that should work and not the ones we > > know that will not work already and thus so far didn't alarm the user > > into thinking something is wrong. > > > > Having the ones we know will fail as pr_debug() seems enough, I'd say. > > This means that: > ``` > $ perf record -e data_read,LLC-prefetch-read -a sleep 0.1 > ``` > will fail (as data_read is a memory controller event and the LLC > doesn't support sampling) with something like: > ``` > Error: > Failure to open any events for recording > ``` > Which feels a bit minimal. As I already mentioned, it is also a > behavior change and so has the potential to break scripts dependent on > the failure information. I don't think it's about failure behavior, the concern is the error messages. It can take too much screen space when users give a long list of invalid events. And unfortunately the current error message for checking dmesg is not very helpful. Anyway you can add this line too: "Use -v to see the details." > > A patch lowering the priority of error messages should be independent > of the 4 changes here. I'd be happy if someone follows this series > with a patch doing it. I think the error behavior is a part of this change. Thanks, Namhyung