perf record: Record dropped sample count

When it uses bpf filters, event might drop some samples.  It'd be nice
if it can report how many samples it lost.  As LOST_SAMPLES event can
carry the similar information, let's use it for bpf filters.

To indicate it's from BPF filters, add a new misc flag for that and
do not display cpu load warnings.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Clark <james.clark@arm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Song Liu <song@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230314234237.3008956-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 24 insertions, 14 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 33ebe42b025e..6df8b823859d 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -52,6 +52,7 @@
 #include "util/pmu-hybrid.h"
 #include "util/evlist-hybrid.h"
 #include "util/off_cpu.h"
+#include "util/bpf-filter.h"
 #include "asm/bug.h"
 #include "perf.h"
 #include "cputopo.h"
@@ -1856,24 +1857,16 @@ record__switch_output(struct record *rec, bool at_exit)
 	return fd;
 }
 
-static void __record__read_lost_samples(struct record *rec, struct evsel *evsel,
+static void __record__save_lost_samples(struct record *rec, struct evsel *evsel,
 					struct perf_record_lost_samples *lost,
-					int cpu_idx, int thread_idx)
+					int cpu_idx, int thread_idx, u64 lost_count,
+					u16 misc_flag)
 {
-	struct perf_counts_values count;
 	struct perf_sample_id *sid;
 	struct perf_sample sample = {};
 	int id_hdr_size;
 
-	if (perf_evsel__read(&evsel->core, cpu_idx, thread_idx, &count) < 0) {
-		pr_debug("read LOST count failed\n");
-		return;
-	}
-
-	if (count.lost == 0)
-		return;
-
-	lost->lost = count.lost;
+	lost->lost = lost_count;
 	if (evsel->core.ids) {
 		sid = xyarray__entry(evsel->core.sample_id, cpu_idx, thread_idx);
 		sample.id = sid->id;
@@ -1882,6 +1875,7 @@ static void __record__read_lost_samples(struct record *rec, struct evsel *evsel,
 	id_hdr_size = perf_event__synthesize_id_sample((void *)(lost + 1),
 						       evsel->core.attr.sample_type, &sample);
 	lost->header.size = sizeof(*lost) + id_hdr_size;
+	lost->header.misc = misc_flag;
 	record__write(rec, NULL, lost, lost->header.size);
 }
 
@@ -1905,6 +1899,7 @@ static void record__read_lost_samples(struct record *rec)
 
 	evlist__for_each_entry(session->evlist, evsel) {
 		struct xyarray *xy = evsel->core.sample_id;
+		u64 lost_count;
 
 		if (xy == NULL || evsel->core.fd == NULL)
 			continue;
@@ -1916,12 +1911,27 @@ static void record__read_lost_samples(struct record *rec)
 
 		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, x, y);
+				struct perf_counts_values count;
+
+				if (perf_evsel__read(&evsel->core, x, y, &count) < 0) {
+					pr_debug("read LOST count failed\n");
+					goto out;
+				}
+
+				if (count.lost) {
+					__record__save_lost_samples(rec, evsel, lost,
+								    x, y, count.lost, 0);
+				}
 			}
 		}
+
+		lost_count = perf_bpf_filter__lost_count(evsel);
+		if (lost_count)
+			__record__save_lost_samples(rec, evsel, lost, 0, 0, lost_count,
+						    PERF_RECORD_MISC_LOST_SAMPLES_BPF);
 	}
+out:
 	free(lost);
-
 }
 
 static volatile sig_atomic_t workload_exec_errno;