On Sat, Nov 15, 2025 at 3:41 PM Namhyung Kim <[email protected]> wrote: > > Add a new event type for deferred callchains and a new callback for the > struct perf_tool. For now it doesn't actually handle the deferred > callchains but it just marks the sample if it has the PERF_CONTEXT_ > USER_DEFFERED in the callchain array. > > At least, perf report can dump the raw data with this change. Actually > this requires the next commit to enable attr.defer_callchain, but if you > already have a data file, it'll show the following result. > > $ perf report -D > ... > [email protected] [0x40]: event: 22 > . > . ... raw event: size 64 bytes > . 0000: 16 00 00 00 02 00 40 00 06 00 00 00 0b 00 00 00 ......@......... > . 0010: 03 00 00 00 00 00 00 00 a7 7f 33 fe 18 7f 00 00 ..........3..... > . 0020: 0f 0e 33 fe 18 7f 00 00 48 14 33 fe 18 7f 00 00 ..3.....H.3..... > . 0030: 08 09 00 00 08 09 00 00 e6 7a e7 35 1c 00 00 00 .........z.5.... > > 121163447014 0x2158 [0x40]: PERF_RECORD_CALLCHAIN_DEFERRED(IP, 0x2): > 2312/2312: 0xb00000006 > ... FP chain: nr:3 > ..... 0: 00007f18fe337fa7 > ..... 1: 00007f18fe330e0f > ..... 2: 00007f18fe331448 > : unhandled! > > Signed-off-by: Namhyung Kim <[email protected]> > --- > tools/lib/perf/include/perf/event.h | 13 ++++++++++ > tools/perf/util/event.c | 1 + > tools/perf/util/evsel.c | 31 +++++++++++++++++++++-- > tools/perf/util/machine.c | 1 + > tools/perf/util/perf_event_attr_fprintf.c | 2 ++ > tools/perf/util/sample.h | 2 ++ > tools/perf/util/session.c | 20 +++++++++++++++ > tools/perf/util/tool.c | 1 + > tools/perf/util/tool.h | 3 ++- > 9 files changed, 71 insertions(+), 3 deletions(-) > > diff --git a/tools/lib/perf/include/perf/event.h > b/tools/lib/perf/include/perf/event.h > index aa1e91c97a226e1a..43a8cb04994fa033 100644 > --- a/tools/lib/perf/include/perf/event.h > +++ b/tools/lib/perf/include/perf/event.h > @@ -151,6 +151,18 @@ struct perf_record_switch { > __u32 next_prev_tid; > }; > > +struct perf_record_callchain_deferred { > + struct perf_event_header header; > + /* > + * This is to match kernel and (deferred) user stacks together. > + * The kernel part will be in the sample callchain array after > + * the PERF_CONTEXT_USER_DEFERRED entry. > + */ > + __u64 cookie; > + __u64 nr; > + __u64 ips[]; > +}; > + > struct perf_record_header_attr { > struct perf_event_header header; > struct perf_event_attr attr; > @@ -523,6 +535,7 @@ union perf_event { > struct perf_record_read read; > struct perf_record_throttle throttle; > struct perf_record_sample sample; > + struct perf_record_callchain_deferred callchain_deferred; > struct perf_record_bpf_event bpf; > struct perf_record_ksymbol ksymbol; > struct perf_record_text_poke_event text_poke; > diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c > index fcf44149feb20c35..4c92cc1a952c1d9f 100644 > --- a/tools/perf/util/event.c > +++ b/tools/perf/util/event.c > @@ -61,6 +61,7 @@ static const char *perf_event__names[] = { > [PERF_RECORD_CGROUP] = "CGROUP", > [PERF_RECORD_TEXT_POKE] = "TEXT_POKE", > [PERF_RECORD_AUX_OUTPUT_HW_ID] = "AUX_OUTPUT_HW_ID", > + [PERF_RECORD_CALLCHAIN_DEFERRED] = "CALLCHAIN_DEFERRED", > [PERF_RECORD_HEADER_ATTR] = "ATTR", > [PERF_RECORD_HEADER_EVENT_TYPE] = "EVENT_TYPE", > [PERF_RECORD_HEADER_TRACING_DATA] = "TRACING_DATA", > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > index 989c56d4a23f74f4..5ee3e7dee93fbbcb 100644 > --- a/tools/perf/util/evsel.c > +++ b/tools/perf/util/evsel.c > @@ -3089,6 +3089,20 @@ int evsel__parse_sample(struct evsel *evsel, union > perf_event *event, > data->data_src = PERF_MEM_DATA_SRC_NONE; > data->vcpu = -1; > > + if (event->header.type == PERF_RECORD_CALLCHAIN_DEFERRED) { > + const u64 max_callchain_nr = UINT64_MAX / sizeof(u64); > + > + data->callchain = (struct ip_callchain > *)&event->callchain_deferred.nr; > + if (data->callchain->nr > max_callchain_nr) > + return -EFAULT; > + > + data->deferred_cookie = event->callchain_deferred.cookie; > + > + if (evsel->core.attr.sample_id_all) > + perf_evsel__parse_id_sample(evsel, event, data); > + return 0; > + } > + > if (event->header.type != PERF_RECORD_SAMPLE) { > if (!evsel->core.attr.sample_id_all) > return 0; > @@ -3213,12 +3227,25 @@ int evsel__parse_sample(struct evsel *evsel, union > perf_event *event, > > if (type & PERF_SAMPLE_CALLCHAIN) { > const u64 max_callchain_nr = UINT64_MAX / sizeof(u64); > + u64 callchain_nr; > > OVERFLOW_CHECK_u64(array); > data->callchain = (struct ip_callchain *)array++; > - if (data->callchain->nr > max_callchain_nr) > + callchain_nr = data->callchain->nr; > + if (callchain_nr > max_callchain_nr) > return -EFAULT; > - sz = data->callchain->nr * sizeof(u64); > + sz = callchain_nr * sizeof(u64); > + /* > + * Save the cookie for the deferred user callchain. The last > 2 > + * entries in the callchain should be the context marker and > the > + * cookie. The cookie will be used to match PERF_RECORD_ > + * CALLCHAIN_DEFERRED later. > + */ > + if (evsel->core.attr.defer_callchain && callchain_nr >= 2 && > + data->callchain->ips[callchain_nr - 2] == > PERF_CONTEXT_USER_DEFERRED) { > + data->deferred_cookie = > data->callchain->ips[callchain_nr - 1]; > + data->deferred_callchain = true; > + } > OVERFLOW_CHECK(array, sz, max_size); > array = (void *)array + sz; > } > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c > index b5dd42588c916d91..841b711d970e9457 100644 > --- a/tools/perf/util/machine.c > +++ b/tools/perf/util/machine.c > @@ -2124,6 +2124,7 @@ static int add_callchain_ip(struct thread *thread, > *cpumode = PERF_RECORD_MISC_KERNEL; > break; > case PERF_CONTEXT_USER: > + case PERF_CONTEXT_USER_DEFERRED: > *cpumode = PERF_RECORD_MISC_USER; > break; > default: > diff --git a/tools/perf/util/perf_event_attr_fprintf.c > b/tools/perf/util/perf_event_attr_fprintf.c > index 66b666d9ce649dd7..741c3d657a8b6ae7 100644 > --- a/tools/perf/util/perf_event_attr_fprintf.c > +++ b/tools/perf/util/perf_event_attr_fprintf.c > @@ -343,6 +343,8 @@ int perf_event_attr__fprintf(FILE *fp, struct > perf_event_attr *attr, > PRINT_ATTRf(inherit_thread, p_unsigned); > PRINT_ATTRf(remove_on_exec, p_unsigned); > PRINT_ATTRf(sigtrap, p_unsigned); > + PRINT_ATTRf(defer_callchain, p_unsigned); > + PRINT_ATTRf(defer_output, p_unsigned); > > PRINT_ATTRn("{ wakeup_events, wakeup_watermark }", wakeup_events, > p_unsigned, false); > PRINT_ATTRf(bp_type, p_unsigned); > diff --git a/tools/perf/util/sample.h b/tools/perf/util/sample.h > index fae834144ef42105..a8307b20a9ea8066 100644 > --- a/tools/perf/util/sample.h > +++ b/tools/perf/util/sample.h > @@ -107,6 +107,8 @@ struct perf_sample { > /** @weight3: On x86 holds retire_lat, on powerpc holds p_stage_cyc. > */ > u16 weight3; > bool no_hw_idx; /* No hw_idx collected in branch_stack */ > + bool deferred_callchain; /* Has deferred user callchains */ > + u64 deferred_cookie; > char insn[MAX_INSN]; > void *raw_data; > struct ip_callchain *callchain; > diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c > index 4b0236b2df2913e1..361e15c1f26a96d0 100644 > --- a/tools/perf/util/session.c > +++ b/tools/perf/util/session.c > @@ -720,6 +720,7 @@ static perf_event__swap_op perf_event__swap_ops[] = { > [PERF_RECORD_CGROUP] = perf_event__cgroup_swap, > [PERF_RECORD_TEXT_POKE] = perf_event__text_poke_swap, > [PERF_RECORD_AUX_OUTPUT_HW_ID] = perf_event__all64_swap, > + [PERF_RECORD_CALLCHAIN_DEFERRED] = perf_event__all64_swap, > [PERF_RECORD_HEADER_ATTR] = perf_event__hdr_attr_swap, > [PERF_RECORD_HEADER_EVENT_TYPE] = perf_event__event_type_swap, > [PERF_RECORD_HEADER_TRACING_DATA] = perf_event__tracing_data_swap, > @@ -854,6 +855,9 @@ static void callchain__printf(struct evsel *evsel, > for (i = 0; i < callchain->nr; i++) > printf("..... %2d: %016" PRIx64 "\n", > i, callchain->ips[i]); > + > + if (sample->deferred_callchain) > + printf("...... (deferred)\n"); > } > > static void branch_stack__printf(struct perf_sample *sample, > @@ -1123,6 +1127,19 @@ static void dump_sample(struct evsel *evsel, union > perf_event *event, > sample_read__printf(sample, evsel->core.attr.read_format); > } > > +static void dump_deferred_callchain(struct evsel *evsel, union perf_event > *event, > + struct perf_sample *sample) > +{ > + if (!dump_trace) > + return; > + > + printf("(IP, 0x%x): %d/%d: %#" PRIx64 "\n", > + event->header.misc, sample->pid, sample->tid, > sample->deferred_cookie); > + > + if (evsel__has_callchain(evsel)) > + callchain__printf(evsel, sample); > +} > + > static void dump_read(struct evsel *evsel, union perf_event *event) > { > struct perf_record_read *read_event = &event->read; > @@ -1353,6 +1370,9 @@ static int machines__deliver_event(struct machines > *machines, > return tool->text_poke(tool, event, sample, machine); > case PERF_RECORD_AUX_OUTPUT_HW_ID: > return tool->aux_output_hw_id(tool, event, sample, machine); > + case PERF_RECORD_CALLCHAIN_DEFERRED: > + dump_deferred_callchain(evsel, event, sample); > + return tool->callchain_deferred(tool, event, sample, evsel, > machine); > default: > ++evlist->stats.nr_unknown_events; > return -1; > diff --git a/tools/perf/util/tool.c b/tools/perf/util/tool.c > index 22a8a4ffe05f778e..f732d33e7f895ed4 100644 > --- a/tools/perf/util/tool.c > +++ b/tools/perf/util/tool.c > @@ -287,6 +287,7 @@ void perf_tool__init(struct perf_tool *tool, bool > ordered_events) > tool->read = process_event_sample_stub; > tool->throttle = process_event_stub; > tool->unthrottle = process_event_stub; > + tool->callchain_deferred = process_event_sample_stub;
nit: there's a similar change needed to delegate_tool__init, that code is currently unused. Reviewed-by: Ian Rogers <[email protected]> Thanks, Ian > tool->attr = process_event_synth_attr_stub; > tool->event_update = process_event_synth_event_update_stub; > tool->tracing_data = process_event_synth_tracing_data_stub; > diff --git a/tools/perf/util/tool.h b/tools/perf/util/tool.h > index 88337cee1e3e2be3..9b9f0a8cbf3de4b5 100644 > --- a/tools/perf/util/tool.h > +++ b/tools/perf/util/tool.h > @@ -44,7 +44,8 @@ enum show_feature_header { > > struct perf_tool { > event_sample sample, > - read; > + read, > + callchain_deferred; > event_op mmap, > mmap2, > comm, > -- > 2.52.0.rc1.455.g30608eb744-goog >
