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Message-ID: <CAP-5=fUWcmi3VfYb92+ndTse1p+=jkb4B0AS3WnAucX7kgAkRA@mail.gmail.com>
Date: Fri, 14 Nov 2025 10:18:27 -0800
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, James Clark <james.clark@...aro.org>,
Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>,
LKML <linux-kernel@...r.kernel.org>, linux-perf-users@...r.kernel.org,
Steven Rostedt <rostedt@...dmis.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
Indu Bhagat <indu.bhagat@...cle.com>, Jens Remus <jremus@...ux.ibm.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, linux-trace-kernel@...r.kernel.org,
bpf@...r.kernel.org
Subject: Re: [PATCH v3 4/5] perf script: Display PERF_RECORD_CALLCHAIN_DEFERRED
On Thu, Nov 13, 2025 at 11:02 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> Handle the deferred callchains in the script output.
>
> $ perf script
> ...
> pwd 2312 121.163435: 249113 cpu/cycles/P:
> ffffffff845b78d8 __build_id_parse.isra.0+0x218 ([kernel.kallsyms])
> ffffffff83bb5bf6 perf_event_mmap+0x2e6 ([kernel.kallsyms])
> ffffffff83c31959 mprotect_fixup+0x1e9 ([kernel.kallsyms])
> ffffffff83c31dc5 do_mprotect_pkey+0x2b5 ([kernel.kallsyms])
> ffffffff83c3206f __x64_sys_mprotect+0x1f ([kernel.kallsyms])
> ffffffff845e6692 do_syscall_64+0x62 ([kernel.kallsyms])
> ffffffff8360012f entry_SYSCALL_64_after_hwframe+0x76 ([kernel.kallsyms])
> b00000006 [unknown] ([unknown])
Does this unknown value correspond to the cookie? Can the cookie and
deferred data be added to the kernel stack trace output?
> pwd 2312 121.163447: DEFERRED CALLCHAIN
> 7f18fe337fa7 mprotect+0x7 (/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2)
> 7f18fe330e0f _dl_sysdep_start+0x7f (/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2)
> 7f18fe331448 _dl_start_user+0x0 (/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2)
Can we display the cookie here so that the user callchain can be
matched with the kernel part?
Thanks,
Ian
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
> tools/perf/builtin-script.c | 89 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 89 insertions(+)
>
> diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> index cf0040bbaba9cbc9..3b2896350bad2924 100644
> --- a/tools/perf/builtin-script.c
> +++ b/tools/perf/builtin-script.c
> @@ -2719,6 +2719,93 @@ static int process_sample_event(const struct perf_tool *tool,
> return ret;
> }
>
> +static int process_deferred_sample_event(const struct perf_tool *tool,
> + union perf_event *event,
> + struct perf_sample *sample,
> + struct evsel *evsel,
> + struct machine *machine)
> +{
> + struct perf_script *scr = container_of(tool, struct perf_script, tool);
> + struct perf_event_attr *attr = &evsel->core.attr;
> + struct evsel_script *es = evsel->priv;
> + unsigned int type = output_type(attr->type);
> + struct addr_location al;
> + FILE *fp = es->fp;
> + int ret = 0;
> +
> + if (output[type].fields == 0)
> + return 0;
> +
> + /* Set thread to NULL to indicate addr_al and al are not initialized */
> + addr_location__init(&al);
> +
> + if (perf_time__ranges_skip_sample(scr->ptime_range, scr->range_num,
> + sample->time)) {
> + goto out_put;
> + }
> +
> + if (debug_mode) {
> + if (sample->time < last_timestamp) {
> + pr_err("Samples misordered, previous: %" PRIu64
> + " this: %" PRIu64 "\n", last_timestamp,
> + sample->time);
> + nr_unordered++;
> + }
> + last_timestamp = sample->time;
> + goto out_put;
> + }
> +
> + if (filter_cpu(sample))
> + goto out_put;
> +
> + if (machine__resolve(machine, &al, sample) < 0) {
> + pr_err("problem processing %d event, skipping it.\n",
> + event->header.type);
> + ret = -1;
> + goto out_put;
> + }
> +
> + if (al.filtered)
> + goto out_put;
> +
> + if (!show_event(sample, evsel, al.thread, &al, NULL))
> + goto out_put;
> +
> + if (evswitch__discard(&scr->evswitch, evsel))
> + goto out_put;
> +
> + perf_sample__fprintf_start(scr, sample, al.thread, evsel,
> + PERF_RECORD_CALLCHAIN_DEFERRED, fp);
> + fprintf(fp, "DEFERRED CALLCHAIN");
> +
> + if (PRINT_FIELD(IP)) {
> + struct callchain_cursor *cursor = NULL;
> +
> + if (symbol_conf.use_callchain && sample->callchain) {
> + cursor = get_tls_callchain_cursor();
> + if (thread__resolve_callchain(al.thread, cursor, evsel,
> + sample, NULL, NULL,
> + scripting_max_stack)) {
> + pr_info("cannot resolve deferred callchains\n");
> + cursor = NULL;
> + }
> + }
> +
> + fputc(cursor ? '\n' : ' ', fp);
> + sample__fprintf_sym(sample, &al, 0, output[type].print_ip_opts,
> + cursor, symbol_conf.bt_stop_list, fp);
> + }
> +
> + fprintf(fp, "\n");
> +
> + if (verbose > 0)
> + fflush(fp);
> +
> +out_put:
> + addr_location__exit(&al);
> + return ret;
> +}
> +
> // Used when scr->per_event_dump is not set
> static struct evsel_script es_stdout;
>
> @@ -4320,6 +4407,7 @@ int cmd_script(int argc, const char **argv)
>
> perf_tool__init(&script.tool, !unsorted_dump);
> script.tool.sample = process_sample_event;
> + script.tool.callchain_deferred = process_deferred_sample_event;
> script.tool.mmap = perf_event__process_mmap;
> script.tool.mmap2 = perf_event__process_mmap2;
> script.tool.comm = perf_event__process_comm;
> @@ -4346,6 +4434,7 @@ int cmd_script(int argc, const char **argv)
> script.tool.throttle = process_throttle_event;
> script.tool.unthrottle = process_throttle_event;
> script.tool.ordering_requires_timestamps = true;
> + script.tool.merge_deferred_callchains = false;
> session = perf_session__new(&data, &script.tool);
> if (IS_ERR(session))
> return PTR_ERR(session);
> --
> 2.52.0.rc1.455.g30608eb744-goog
>
>
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