[PATCH 3/5] perf record: Read and inject LOST_SAMPLES events

Namhyung Kim
2022-08-31T21:04:14Z

When there are lost samples, it can read the number of PERF_FORMAT_LOST and
convert it to PERF_RECORD_LOST_SAMPLES and write to the data file at the end.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/builtin-record.c | 60 +++++++++++++++++++++++++++++++++++++
1 file changed, 60 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index bce8c941d558..cb9881543a07 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -10,6 +10,7 @@

#include "util/build-id.h"
#include <subcmd/parse-options.h>
+#include <internal/xyarray.h>
#include "util/parse-events.h"
#include "util/config.h"

@@ -1852,6 +1853,64 @@ record__switch_output(struct record *rec, bool at_exit)
return fd;
}

+static void __record__read_lost_samples(struct record *rec, struct evsel *evsel,
+ struct perf_record_lost_samples *lost,
+ int size, int cpu_idx, int thread_idx)
+{
+ struct perf_counts_values count;
+ struct perf_sample_id *sid;
+ struct perf_sample sample = {};
+
+ if (perf_evsel__read(&evsel->core, cpu_idx, thread_idx, &count) < 0) {
+ pr_err("read LOST count failed\n");
+ return;
+ }
+
+ if (count.lost == 0)
+ return;
+
+ lost->lost = count.lost;
+ if (evsel->core.ids) {
+ sid = xyarray__entry(evsel->core.sample_id, cpu_idx, thread_idx);
+ sample.id = sid->id;
+ }
+
+ perf_event__synthesize_id_sample((void *)(lost + 1),
+ evsel->core.attr.sample_type, &sample);
+ record__write(rec, NULL, lost, size);
+}
+
+static void record__read_lost_samples(struct record *rec)
+{
+ struct perf_session *session = rec->session;
+ struct machine *machine = &session->machines.host;
+ struct perf_record_lost_samples *lost;
+ struct evsel *evsel;
+ int size = sizeof(*lost) + machine->id_hdr_size;
+
+ lost = zalloc(size);
+ lost->header.type = PERF_RECORD_LOST_SAMPLES;
+ lost->header.size = size;
+
+ evlist__for_each_entry(session->evlist, evsel) {
+ struct xyarray *xy = evsel->core.sample_id;
+
+ if (xyarray__max_x(evsel->core.fd) != xyarray__max_x(xy) ||
+ xyarray__max_y(evsel->core.fd) != xyarray__max_y(xy)) {
+ pr_debug("Unmatched FD vs. sample ID: skip reading LOST count\n");
+ continue;
+ }
+
+ for (int x = 0; x < xyarray__max_x(xy); x++) {
+ for (int y = 0; y < xyarray__max_y(xy); y++) {
+ __record__read_lost_samples(rec, evsel, lost,
+ size, x, y);
+ }
+ }
+ }
+
+}
+
static volatile int workload_exec_errno;

/*
@@ -2710,6 +2769,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
if (rec->off_cpu)
rec->bytes_written += off_cpu_write(rec->session);

+ record__read_lost_samples(rec);
record__synthesize(rec, true);
/* this will be recalculated during process_buildids() */
rec->samples = 0;
--
2.37.2.789.g6183377224-goog