On Wed, Nov 19, 2025 at 08:48:35AM -0800, Ian Rogers wrote: > 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.
Will update in v2. > > Reviewed-by: Ian Rogers <[email protected]> Thanks for the review! Namhyung > > > 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 > >
