On Thu, Nov 20, 2025 at 3:48 PM Namhyung Kim <[email protected]> wrote: > > Save samples with deferred callchains in a separate list and deliver > them after merging the user callchains. If users don't want to merge > they can set tool->merge_deferred_callchains to false to prevent the > behavior. > > With previous result, now perf script will show the merged callchains. > > $ 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]) > 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) > ... > > The old output can be get using --no-merge-callchain option. > Also perf report can get the user callchain entry at the end. > > $ perf report --no-children --stdio -q -S __build_id_parse.isra.0 > # symbol: __build_id_parse.isra.0 > 8.40% pwd [kernel.kallsyms] > | > ---__build_id_parse.isra.0 > perf_event_mmap > mprotect_fixup > do_mprotect_pkey > __x64_sys_mprotect > do_syscall_64 > entry_SYSCALL_64_after_hwframe > mprotect > _dl_sysdep_start > _dl_start_user > > Signed-off-by: Namhyung Kim <[email protected]>
Reviewed-by: Ian Rogers <[email protected]> > --- > tools/perf/Documentation/perf-script.txt | 5 ++ > tools/perf/builtin-inject.c | 1 + > tools/perf/builtin-report.c | 1 + > tools/perf/builtin-script.c | 4 ++ > tools/perf/util/callchain.c | 29 +++++++++ > tools/perf/util/callchain.h | 3 + > tools/perf/util/evlist.c | 1 + > tools/perf/util/evlist.h | 2 + > tools/perf/util/session.c | 79 +++++++++++++++++++++++- > tools/perf/util/tool.c | 2 + > tools/perf/util/tool.h | 1 + > 11 files changed, 127 insertions(+), 1 deletion(-) > > diff --git a/tools/perf/Documentation/perf-script.txt > b/tools/perf/Documentation/perf-script.txt > index 28bec7e78bc858ba..03d1129606328d6d 100644 > --- a/tools/perf/Documentation/perf-script.txt > +++ b/tools/perf/Documentation/perf-script.txt > @@ -527,6 +527,11 @@ include::itrace.txt[] > The known limitations include exception handing such as > setjmp/longjmp will have calls/returns not match. > > +--merge-callchains:: > + Enable merging deferred user callchains if available. This is the > + default behavior. If you want to see separate CALLCHAIN_DEFERRED > + records for some reason, use --no-merge-callchains explicitly. > + > :GMEXAMPLECMD: script > :GMEXAMPLESUBCMD: > include::guest-files.txt[] > diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c > index bd9245d2dd41aa48..51d2721b6db9dccb 100644 > --- a/tools/perf/builtin-inject.c > +++ b/tools/perf/builtin-inject.c > @@ -2527,6 +2527,7 @@ int cmd_inject(int argc, const char **argv) > inject.tool.auxtrace = perf_event__repipe_auxtrace; > inject.tool.bpf_metadata = perf_event__repipe_op2_synth; > inject.tool.dont_split_sample_group = true; > + inject.tool.merge_deferred_callchains = false; > inject.session = __perf_session__new(&data, &inject.tool, > > /*trace_event_repipe=*/inject.output.is_pipe, > /*host_env=*/NULL); > diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c > index 2bc269f5fcef8023..add6b1c2aaf04270 100644 > --- a/tools/perf/builtin-report.c > +++ b/tools/perf/builtin-report.c > @@ -1614,6 +1614,7 @@ int cmd_report(int argc, const char **argv) > report.tool.event_update = perf_event__process_event_update; > report.tool.feature = process_feature_event; > report.tool.ordering_requires_timestamps = true; > + report.tool.merge_deferred_callchains = !dump_trace; > > session = perf_session__new(&data, &report.tool); > if (IS_ERR(session)) { > diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c > index 85b42205a71b3993..62e43d3c5ad731a0 100644 > --- a/tools/perf/builtin-script.c > +++ b/tools/perf/builtin-script.c > @@ -4009,6 +4009,7 @@ int cmd_script(int argc, const char **argv) > bool header_only = false; > bool script_started = false; > bool unsorted_dump = false; > + bool merge_deferred_callchains = true; > char *rec_script_path = NULL; > char *rep_script_path = NULL; > struct perf_session *session; > @@ -4162,6 +4163,8 @@ int cmd_script(int argc, const char **argv) > "Guest code can be found in hypervisor process"), > OPT_BOOLEAN('\0', "stitch-lbr", &script.stitch_lbr, > "Enable LBR callgraph stitching approach"), > + OPT_BOOLEAN('\0', "merge-callchains", &merge_deferred_callchains, > + "Enable merge deferred user callchains"), > OPTS_EVSWITCH(&script.evswitch), > OPT_END() > }; > @@ -4418,6 +4421,7 @@ 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 = merge_deferred_callchains; > session = perf_session__new(&data, &script.tool); > if (IS_ERR(session)) > return PTR_ERR(session); > diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c > index 2884187ccbbecfdc..71dc5a070065dd2a 100644 > --- a/tools/perf/util/callchain.c > +++ b/tools/perf/util/callchain.c > @@ -1838,3 +1838,32 @@ int sample__for_each_callchain_node(struct thread > *thread, struct evsel *evsel, > } > return 0; > } > + > +int sample__merge_deferred_callchain(struct perf_sample *sample_orig, nit: We use the term deferred rather than original except in this context. I think deferred is a little more intention revealing than original. Perhaps add a comment capturing that the original sample is the deferred kernel sample. Thanks, Ian > + struct perf_sample *sample_callchain) > +{ > + u64 nr_orig = sample_orig->callchain->nr - 1; > + u64 nr_deferred = sample_callchain->callchain->nr; > + struct ip_callchain *callchain; > + > + if (sample_orig->callchain->nr < 2) { > + sample_orig->deferred_callchain = false; > + return -EINVAL; > + } > + > + callchain = calloc(1 + nr_orig + nr_deferred, sizeof(u64)); > + if (callchain == NULL) { > + sample_orig->deferred_callchain = false; > + return -ENOMEM; > + } > + > + callchain->nr = nr_orig + nr_deferred; > + /* copy original including PERF_CONTEXT_USER_DEFERRED (but the > cookie) */ > + memcpy(callchain->ips, sample_orig->callchain->ips, nr_orig * > sizeof(u64)); > + /* copy deferred user callchains */ > + memcpy(&callchain->ips[nr_orig], sample_callchain->callchain->ips, > + nr_deferred * sizeof(u64)); > + > + sample_orig->callchain = callchain; > + return 0; > +} > diff --git a/tools/perf/util/callchain.h b/tools/perf/util/callchain.h > index d5ae4fbb7ce5fa44..2a52af8c80ace33c 100644 > --- a/tools/perf/util/callchain.h > +++ b/tools/perf/util/callchain.h > @@ -318,4 +318,7 @@ int sample__for_each_callchain_node(struct thread > *thread, struct evsel *evsel, > struct perf_sample *sample, int max_stack, > bool symbols, callchain_iter_fn cb, void > *data); > > +int sample__merge_deferred_callchain(struct perf_sample *sample_orig, > + struct perf_sample *sample_callchain); > + > #endif /* __PERF_CALLCHAIN_H */ > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c > index e8217efdda5323c6..03674d2cbd015e4f 100644 > --- a/tools/perf/util/evlist.c > +++ b/tools/perf/util/evlist.c > @@ -85,6 +85,7 @@ void evlist__init(struct evlist *evlist, struct > perf_cpu_map *cpus, > evlist->ctl_fd.pos = -1; > evlist->nr_br_cntr = -1; > metricgroup__rblist_init(&evlist->metric_events); > + INIT_LIST_HEAD(&evlist->deferred_samples); > } > > struct evlist *evlist__new(void) > diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h > index 5e71e3dc60423079..911834ae7c2a6f76 100644 > --- a/tools/perf/util/evlist.h > +++ b/tools/perf/util/evlist.h > @@ -92,6 +92,8 @@ struct evlist { > * of struct metric_expr. > */ > struct rblist metric_events; > + /* samples with deferred_callchain would wait here. */ > + struct list_head deferred_samples; > }; > > struct evsel_str_handler { > diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c > index 361e15c1f26a96d0..dc570ad47ccc2c63 100644 > --- a/tools/perf/util/session.c > +++ b/tools/perf/util/session.c > @@ -1285,6 +1285,66 @@ static int evlist__deliver_sample(struct evlist > *evlist, const struct perf_tool > per_thread); > } > > +/* > + * Samples with deferred callchains should wait for the next matching > + * PERF_RECORD_CALLCHAIN_RECORD entries. Keep the events in a list and > + * deliver them once it finds the callchains. > + */ > +struct deferred_event { > + struct list_head list; > + union perf_event *event; > +}; > + > +static int evlist__deliver_deferred_callchain(struct evlist *evlist, > + const struct perf_tool *tool, > + union perf_event *event, > + struct perf_sample *sample, > + struct machine *machine) > +{ > + struct deferred_event *de, *tmp; > + struct evsel *evsel; > + int ret = 0; > + > + if (!tool->merge_deferred_callchains) { > + evsel = evlist__id2evsel(evlist, sample->id); > + return tool->callchain_deferred(tool, event, sample, > + evsel, machine); > + } > + > + list_for_each_entry_safe(de, tmp, &evlist->deferred_samples, list) { > + struct perf_sample orig_sample; > + > + ret = evlist__parse_sample(evlist, de->event, &orig_sample); > + if (ret < 0) { > + pr_err("failed to parse original sample\n"); > + break; > + } > + > + if (sample->tid != orig_sample.tid) > + continue; > + > + if (event->callchain_deferred.cookie == > orig_sample.deferred_cookie) > + sample__merge_deferred_callchain(&orig_sample, > sample); > + else > + orig_sample.deferred_callchain = false; > + > + evsel = evlist__id2evsel(evlist, orig_sample.id); > + ret = evlist__deliver_sample(evlist, tool, de->event, > + &orig_sample, evsel, machine); > + > + if (orig_sample.deferred_callchain) > + free(orig_sample.callchain); > + > + list_del(&de->list); > + free(de->event); > + free(de); > + > + if (ret) > + break; > + } > + return ret; > +} > + > static int machines__deliver_event(struct machines *machines, > struct evlist *evlist, > union perf_event *event, > @@ -1313,6 +1373,22 @@ static int machines__deliver_event(struct machines > *machines, > return 0; > } > dump_sample(evsel, event, sample, > perf_env__arch(machine->env)); > + if (sample->deferred_callchain && > tool->merge_deferred_callchains) { > + struct deferred_event *de = malloc(sizeof(*de)); > + size_t sz = event->header.size; > + > + if (de == NULL) > + return -ENOMEM; > + > + de->event = malloc(sz); > + if (de->event == NULL) { > + free(de); > + return -ENOMEM; > + } > + memcpy(de->event, event, sz); > + list_add_tail(&de->list, &evlist->deferred_samples); > + return 0; > + } > return evlist__deliver_sample(evlist, tool, event, sample, > evsel, machine); > case PERF_RECORD_MMAP: > return tool->mmap(tool, event, sample, machine); > @@ -1372,7 +1448,8 @@ static int machines__deliver_event(struct machines > *machines, > 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); > + return evlist__deliver_deferred_callchain(evlist, tool, event, > + sample, machine); > default: > ++evlist->stats.nr_unknown_events; > return -1; > diff --git a/tools/perf/util/tool.c b/tools/perf/util/tool.c > index e77f0e2ecc1f79db..27ba5849c74a2e7d 100644 > --- a/tools/perf/util/tool.c > +++ b/tools/perf/util/tool.c > @@ -266,6 +266,7 @@ void perf_tool__init(struct perf_tool *tool, bool > ordered_events) > tool->cgroup_events = false; > tool->no_warn = false; > tool->show_feat_hdr = SHOW_FEAT_NO_HEADER; > + tool->merge_deferred_callchains = true; > > tool->sample = process_event_sample_stub; > tool->mmap = process_event_stub; > @@ -448,6 +449,7 @@ void delegate_tool__init(struct delegate_tool *tool, > struct perf_tool *delegate) > tool->tool.cgroup_events = delegate->cgroup_events; > tool->tool.no_warn = delegate->no_warn; > tool->tool.show_feat_hdr = delegate->show_feat_hdr; > + tool->tool.merge_deferred_callchains = > delegate->merge_deferred_callchains; > > tool->tool.sample = delegate_sample; > tool->tool.read = delegate_read; > diff --git a/tools/perf/util/tool.h b/tools/perf/util/tool.h > index 9b9f0a8cbf3de4b5..e96b69d25a5b737d 100644 > --- a/tools/perf/util/tool.h > +++ b/tools/perf/util/tool.h > @@ -90,6 +90,7 @@ struct perf_tool { > bool cgroup_events; > bool no_warn; > bool dont_split_sample_group; > + bool merge_deferred_callchains; > enum show_feature_header show_feat_hdr; > }; > > -- > 2.52.0.rc2.455.g230fcf2819-goog >
