perf tools: handle PERF_RECORD_LOST_SAMPLES
This patch modifies the perf tool to handle the new RECORD type, PERF_RECORD_LOST_SAMPLES. The number of lost-sample events is stored in .nr_events[PERF_RECORD_LOST_SAMPLES]. The exact number of samples which the kernel dropped is stored in total_lost_samples. When the percentage of dropped samples is greater than 5%, a warning is printed. Here are some examples: Eg 1, Recording different frequently-occurring events is safe with the patch. Only a very low drop rate is associated with such actions. $ perf record -e '{cycles:p,instructions:p}' -c 20003 --no-time ~/tchain ~/tchain $ perf report -D | tail SAMPLE events: 120243 MMAP2 events: 5 LOST_SAMPLES events: 24 FINISHED_ROUND events: 15 cycles:p stats: TOTAL events: 59348 SAMPLE events: 59348 instructions:p stats: TOTAL events: 60895 SAMPLE events: 60895 $ perf report --stdio --group # To display the perf.data header info, please use --header/--header-only options. # # # Total Lost Samples: 24 # # Samples: 120K of event 'anon group { cycles:p, instructions:p }' # Event count (approx.): 24048600000 # # Overhead Command Shared Object Symbol # ................ ........... ................ .................................. # 99.74% 99.86% tchain_edit tchain_edit [.] f3 0.09% 0.02% tchain_edit tchain_edit [.] f2 0.04% 0.00% tchain_edit [kernel.vmlinux] [k] ixgbe_read_reg Eg 2, Recording the same thing multiple times can lead to high drop rate, but it is not a useful configuration. $ perf record -e '{cycles:p,cycles:p}' -c 20003 --no-time ~/tchain Warning: Processed 600592 samples and lost 99.73% samples! [perf record: Woken up 148 times to write data] [perf record: Captured and wrote 36.922 MB perf.data (1206322 samples)] [perf record: Woken up 1 times to write data] [perf record: Captured and wrote 0.121 MB perf.data (1629 samples)] Signed-off-by: Kan Liang <kan.liang@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: acme@infradead.org Cc: eranian@google.com Link: http://lkml.kernel.org/r/1431285195-14269-9-git-send-email-kan.liang@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -320,6 +320,7 @@ static int perf_evlist__tty_browse_hists(struct perf_evlist *evlist,
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{
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struct perf_evsel *pos;
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fprintf(stdout, "#\n# Total Lost Samples: %lu\n#\n", evlist->stats.total_lost_samples);
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evlist__for_each(evlist, pos) {
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struct hists *hists = evsel__hists(pos);
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const char *evname = perf_evsel__name(pos);
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@ -25,6 +25,7 @@ static const char *perf_event__names[] = {
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[PERF_RECORD_SAMPLE] = "SAMPLE",
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[PERF_RECORD_AUX] = "AUX",
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[PERF_RECORD_ITRACE_START] = "ITRACE_START",
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[PERF_RECORD_LOST_SAMPLES] = "LOST_SAMPLES",
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[PERF_RECORD_HEADER_ATTR] = "ATTR",
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[PERF_RECORD_HEADER_EVENT_TYPE] = "EVENT_TYPE",
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[PERF_RECORD_HEADER_TRACING_DATA] = "TRACING_DATA",
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@ -712,6 +713,14 @@ int perf_event__process_itrace_start(struct perf_tool *tool __maybe_unused,
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return machine__process_itrace_start_event(machine, event);
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}
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int perf_event__process_lost_samples(struct perf_tool *tool __maybe_unused,
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union perf_event *event,
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struct perf_sample *sample,
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struct machine *machine)
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{
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return machine__process_lost_samples_event(machine, event, sample);
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}
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size_t perf_event__fprintf_mmap(union perf_event *event, FILE *fp)
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{
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return fprintf(fp, " %d/%d: [%#" PRIx64 "(%#" PRIx64 ") @ %#" PRIx64 "]: %c %s\n",
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@ -52,6 +52,11 @@ struct lost_event {
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u64 lost;
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};
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struct lost_samples_event {
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struct perf_event_header header;
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u64 lost;
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};
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/*
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* PERF_FORMAT_ENABLED | PERF_FORMAT_RUNNING | PERF_FORMAT_ID
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*/
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@ -235,6 +240,12 @@ enum auxtrace_error_type {
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* total_lost tells exactly how many events the kernel in fact lost, i.e. it is
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* the sum of all struct lost_event.lost fields reported.
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*
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* The kernel discards mixed up samples and sends the number in a
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* PERF_RECORD_LOST_SAMPLES event. The number of lost-samples events is stored
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* in .nr_events[PERF_RECORD_LOST_SAMPLES] while total_lost_samples tells
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* exactly how many samples the kernel in fact dropped, i.e. it is the sum of
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* all struct lost_samples_event.lost fields reported.
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*
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* The total_period is needed because by default auto-freq is used, so
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* multipling nr_events[PERF_EVENT_SAMPLE] by a frequency isn't possible to get
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* the total number of low level events, it is necessary to to sum all struct
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@ -244,6 +255,7 @@ struct events_stats {
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u64 total_period;
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u64 total_non_filtered_period;
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u64 total_lost;
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u64 total_lost_samples;
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u64 total_invalid_chains;
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u32 nr_events[PERF_RECORD_HEADER_MAX];
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u32 nr_non_filtered_samples;
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@ -342,6 +354,7 @@ union perf_event {
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struct comm_event comm;
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struct fork_event fork;
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struct lost_event lost;
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struct lost_samples_event lost_samples;
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struct read_event read;
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struct throttle_event throttle;
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struct sample_event sample;
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@ -390,6 +403,10 @@ int perf_event__process_lost(struct perf_tool *tool,
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union perf_event *event,
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struct perf_sample *sample,
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struct machine *machine);
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int perf_event__process_lost_samples(struct perf_tool *tool,
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union perf_event *event,
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struct perf_sample *sample,
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struct machine *machine);
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int perf_event__process_aux(struct perf_tool *tool,
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union perf_event *event,
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struct perf_sample *sample,
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@ -482,6 +482,14 @@ int machine__process_lost_event(struct machine *machine __maybe_unused,
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return 0;
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}
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int machine__process_lost_samples_event(struct machine *machine __maybe_unused,
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union perf_event *event, struct perf_sample *sample)
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{
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dump_printf(": id:%" PRIu64 ": lost samples :%" PRIu64 "\n",
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sample->id, event->lost_samples.lost);
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return 0;
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}
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static struct dso*
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machine__module_dso(struct machine *machine, struct kmod_path *m,
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const char *filename)
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@ -1419,6 +1427,8 @@ int machine__process_event(struct machine *machine, union perf_event *event,
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ret = machine__process_aux_event(machine, event); break;
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case PERF_RECORD_ITRACE_START:
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ret = machine__process_itrace_start_event(machine, event);
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case PERF_RECORD_LOST_SAMPLES:
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ret = machine__process_lost_samples_event(machine, event, sample); break;
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break;
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default:
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ret = -1;
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@ -81,6 +81,8 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
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struct perf_sample *sample);
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int machine__process_lost_event(struct machine *machine, union perf_event *event,
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struct perf_sample *sample);
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int machine__process_lost_samples_event(struct machine *machine, union perf_event *event,
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struct perf_sample *sample);
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int machine__process_aux_event(struct machine *machine,
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union perf_event *event);
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int machine__process_itrace_start_event(struct machine *machine,
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@ -325,6 +325,8 @@ void perf_tool__fill_defaults(struct perf_tool *tool)
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tool->exit = process_event_stub;
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if (tool->lost == NULL)
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tool->lost = perf_event__process_lost;
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if (tool->lost_samples == NULL)
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tool->lost_samples = perf_event__process_lost_samples;
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if (tool->aux == NULL)
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tool->aux = perf_event__process_aux;
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if (tool->itrace_start == NULL)
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@ -606,6 +608,7 @@ static perf_event__swap_op perf_event__swap_ops[] = {
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[PERF_RECORD_SAMPLE] = perf_event__all64_swap,
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[PERF_RECORD_AUX] = perf_event__aux_swap,
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[PERF_RECORD_ITRACE_START] = perf_event__itrace_start_swap,
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[PERF_RECORD_LOST_SAMPLES] = perf_event__all64_swap,
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[PERF_RECORD_HEADER_ATTR] = perf_event__hdr_attr_swap,
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[PERF_RECORD_HEADER_EVENT_TYPE] = perf_event__event_type_swap,
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[PERF_RECORD_HEADER_TRACING_DATA] = perf_event__tracing_data_swap,
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@ -1049,6 +1052,10 @@ static int machines__deliver_event(struct machines *machines,
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if (tool->lost == perf_event__process_lost)
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evlist->stats.total_lost += event->lost.lost;
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return tool->lost(tool, event, sample, machine);
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case PERF_RECORD_LOST_SAMPLES:
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if (tool->lost_samples == perf_event__process_lost_samples)
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evlist->stats.total_lost_samples += event->lost_samples.lost;
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return tool->lost_samples(tool, event, sample, machine);
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case PERF_RECORD_READ:
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return tool->read(tool, event, sample, evsel, machine);
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case PERF_RECORD_THROTTLE:
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@ -1286,6 +1293,18 @@ static void perf_session__warn_about_errors(const struct perf_session *session)
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stats->nr_events[PERF_RECORD_LOST]);
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}
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if (session->tool->lost_samples == perf_event__process_lost_samples) {
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double drop_rate;
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drop_rate = (double)stats->total_lost_samples /
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(double) (stats->nr_events[PERF_RECORD_SAMPLE] + stats->total_lost_samples);
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if (drop_rate > 0.05) {
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ui__warning("Processed %lu samples and lost %3.2f%% samples!\n\n",
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stats->nr_events[PERF_RECORD_SAMPLE] + stats->total_lost_samples,
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drop_rate * 100.0);
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}
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}
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if (stats->nr_unknown_events != 0) {
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ui__warning("Found %u unknown events!\n\n"
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"Is this an older tool processing a perf.data "
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@ -43,6 +43,7 @@ struct perf_tool {
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fork,
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exit,
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lost,
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lost_samples,
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aux,
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itrace_start,
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throttle,
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