Add loggings of statistics of socket tracer data event sizes

Test Plan: Tested manually and see the printed logs

Reviewers: #stirling, oazizi

Reviewed By: #stirling, oazizi
Signed-off-by: yzhao1012 <yzhao@pixielabs.ai>

Differential Revision: https://phab.corp.pixielabs.ai/D10835

GitOrigin-RevId: b0055efd43ed692a28d42b95501c52c462b6b534

src/stirling/source_connectors/socket_tracer/socket_trace_connector.cc

@@ -666,10 +666,11 @@ Status SocketTraceConnector::DisableSelfTracing() {
 // Perf Buffer Polling and Callback functions.
 //-----------------------------------------------------------------------------
 
-void SocketTraceConnector::HandleDataEvent(void* cb_cookie, void* data, int /*data_size*/) {
+void SocketTraceConnector::HandleDataEvent(void* cb_cookie, void* data, int data_size) {
   DCHECK(cb_cookie != nullptr) << "Perf buffer callback not set-up properly. Missing cb_cookie.";
   auto* connector = static_cast<SocketTraceConnector*>(cb_cookie);
   auto data_event_ptr = std::make_unique<SocketDataEvent>(data);
+  connector->stats_.Increment(StatKey::kPollSocketDataEventSize, data_size);
   connector->AcceptDataEvent(std::move(data_event_ptr));
 }
 
@@ -775,6 +776,10 @@ void SocketTraceConnector::AcceptDataEvent(std::unique_ptr<SocketDataEvent> even
     WriteDataEvent(*event);
   }
 
+  stats_.Increment(StatKey::kPollSocketDataEventCount);
+  stats_.Increment(StatKey::kPollSocketDataEventAttrSize, sizeof(event->attr));
+  stats_.Increment(StatKey::kPollSocketDataEventDataSize, event->msg.size());
+
   ConnTracker& tracker = GetOrCreateConnTracker(event->attr.conn_id);
   tracker.AddDataEvent(std::move(event));
 }

src/stirling/source_connectors/socket_tracer/socket_trace_connector.h

@@ -251,6 +251,11 @@ class SocketTraceConnector : public SourceConnector, public bpf_tools::BCCWrappe
     kLossConnStatsEvent,
     kLossMMapEvent,
     kLossHTTP2Event,
+
+    kPollSocketDataEventCount,
+    kPollSocketDataEventAttrSize,
+    kPollSocketDataEventDataSize,
+    kPollSocketDataEventSize,
   };
 
   utils::StatCounter<StatKey> stats_;