Messages in this thread Patch in this message | | | From | Ravi Bangoria <> | Subject | [RFC] perf record: Use PERF_RECORD_LOST for synthesizing samples from read_format->lost | Date | Fri, 23 Jun 2023 13:50:31 +0530 |
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Currently perf synthesizes PERF_RECORD_LOST_SAMPLES samples for values returned by read_format->lost. IIUC, PERF_RECORD_LOST_SAMPLES is used only when hw provides corrupted samples and thus kernel has to drop those. OTOH, PERF_RECORD_LOST is used when kernel has valid samples but it fails to push them to ring-buffer because ring-buffer is already full.
So I feel PERF_RECORD_LOST is more appropriate for synthesizing samples from read_format->lost.
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com> --- Notes: - Posting this as RFC to get feedback. I haven't tested it well. - There is one more minor issue: Aggregated Stats shows count of LOST/ LOST_SAMPLES records instead of actual number of lost events/samples: ``` $ sudo ./perf report -D | tail -20 Warning: Processed 78923 events and lost 1153 chunks! Warning: Processed 47427 samples and lost 28.30%! ... Aggregated stats: LOST events: 1153 ( 1.5%) LOST_SAMPLES events: 132 ( 0.2%) ``` Not sure if this is intentional.
tools/perf/builtin-record.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index efa03e4ac2c9..5baed42437b2 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -1858,7 +1858,7 @@ record__switch_output(struct record *rec, bool at_exit) } static void __record__save_lost_samples(struct record *rec, struct evsel *evsel, - struct perf_record_lost_samples *lost, + struct perf_record_lost *lost, int cpu_idx, int thread_idx, u64 lost_count, u16 misc_flag) { @@ -1871,6 +1871,7 @@ static void __record__save_lost_samples(struct record *rec, struct evsel *evsel, sid = xyarray__entry(evsel->core.sample_id, cpu_idx, thread_idx); sample.id = sid->id; } + lost->id = sid->id; id_hdr_size = perf_event__synthesize_id_sample((void *)(lost + 1), evsel->core.attr.sample_type, &sample); @@ -1882,7 +1883,7 @@ static void __record__save_lost_samples(struct record *rec, struct evsel *evsel, static void record__read_lost_samples(struct record *rec) { struct perf_session *session = rec->session; - struct perf_record_lost_samples *lost; + struct perf_record_lost *lost; struct evsel *evsel; /* there was an error during record__open */ @@ -1895,7 +1896,7 @@ static void record__read_lost_samples(struct record *rec) return; } - lost->header.type = PERF_RECORD_LOST_SAMPLES; + lost->header.type = PERF_RECORD_LOST; evlist__for_each_entry(session->evlist, evsel) { struct xyarray *xy = evsel->core.sample_id; -- 2.41.0
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