SF: Only create a starting entry if there are starting states

Test: atest TransactionTracingTest
Bug: 200284593
Change-Id: Ie260fb094117ec754778f8277602d10df6606fb2

2 files changed, 17 insertions, 16 deletions

diff --git a/services/surfaceflinger/Tracing/TransactionTracing.cpp b/services/surfaceflinger/Tracing/TransactionTracing.cpp
index 5136295592..a46b79578f 100644
--- a/services/surfaceflinger/Tracing/TransactionTracing.cpp
+++ b/services/surfaceflinger/Tracing/TransactionTracing.cpp
@@ -128,7 +128,9 @@ void TransactionTracing::loop() {
             mCommittedTransactions.clear();
         } // unlock mMainThreadLock
 
-        addEntry(committedTransactions, removedLayers);
+        if (!committedTransactions.empty() || !removedLayers.empty()) {
+            addEntry(committedTransactions, removedLayers);
+        }
     }
 }
 
@@ -275,6 +277,7 @@ int32_t TransactionTracing::getLayerIdLocked(const sp<IBinder>& layerHandle) {
 
 void TransactionTracing::updateStartingStateLocked(
         const proto::TransactionTraceEntry& removedEntry) {
+    mStartingTimestamp = removedEntry.elapsed_realtime_nanos();
     // Keep track of layer starting state so we can reconstruct the layer state as we purge
     // transactions from the buffer.
     for (const proto::LayerCreationArgs& addedLayer : removedEntry.added_layers()) {
@@ -303,13 +306,14 @@ void TransactionTracing::updateStartingStateLocked(
 }
 
 void TransactionTracing::addStartingStateToProtoLocked(proto::TransactionTraceFile& proto) {
-    proto::TransactionTraceEntry* entryProto = proto.add_entry();
-    entryProto->set_elapsed_realtime_nanos(mStartingTimestamp);
-    entryProto->set_vsync_id(0);
     if (mStartingStates.size() == 0) {
         return;
     }
 
+    proto::TransactionTraceEntry* entryProto = proto.add_entry();
+    entryProto->set_elapsed_realtime_nanos(mStartingTimestamp);
+    entryProto->set_vsync_id(0);
+
     entryProto->mutable_added_layers()->Reserve(static_cast<int32_t>(mStartingStates.size()));
     for (auto& [layerId, state] : mStartingStates) {
         entryProto->mutable_added_layers()->Add(TransactionProtoParser::toProto(state.args));
diff --git a/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp b/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
index 5ac581288e..39dbb07653 100644
--- a/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
+++ b/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
@@ -91,10 +91,9 @@ TEST_F(TransactionTracingTest, addTransactions) {
     flush(secondTransactionSetVsyncId);
 
     proto::TransactionTraceFile proto = writeToProto();
-    EXPECT_EQ(proto.entry().size(), 3);
-    // skip starting entry
-    verifyEntry(proto.entry(1), firstTransactionSet, firstTransactionSetVsyncId);
-    verifyEntry(proto.entry(2), secondTransactionSet, secondTransactionSetVsyncId);
+    EXPECT_EQ(proto.entry().size(), 2);
+    verifyEntry(proto.entry(0), firstTransactionSet, firstTransactionSetVsyncId);
+    verifyEntry(proto.entry(1), secondTransactionSet, secondTransactionSetVsyncId);
 }
 
 class TransactionTracingLayerHandlingTest : public TransactionTracingTest {
@@ -274,15 +273,13 @@ protected:
 TEST_F(TransactionTracingMirrorLayerTest, canAddMirrorLayers) {
     proto::TransactionTraceFile proto = writeToProto();
     // We don't have any starting states since no layer was removed from.
-    EXPECT_EQ(proto.entry().size(), 2);
-    EXPECT_EQ(proto.entry(0).transactions().size(), 0);
-    EXPECT_EQ(proto.entry(0).added_layers().size(), 0);
+    EXPECT_EQ(proto.entry().size(), 1);
 
     // Verify the mirror layer was added
-    EXPECT_EQ(proto.entry(1).transactions().size(), 1);
-    EXPECT_EQ(proto.entry(1).added_layers().size(), 2);
-    EXPECT_EQ(proto.entry(1).added_layers(1).layer_id(), mMirrorLayerId);
-    EXPECT_EQ(proto.entry(1).transactions(0).layer_changes().size(), 2);
-    EXPECT_EQ(proto.entry(1).transactions(0).layer_changes(1).z(), 43);
+    EXPECT_EQ(proto.entry(0).transactions().size(), 1);
+    EXPECT_EQ(proto.entry(0).added_layers().size(), 2);
+    EXPECT_EQ(proto.entry(0).added_layers(1).layer_id(), mMirrorLayerId);
+    EXPECT_EQ(proto.entry(0).transactions(0).layer_changes().size(), 2);
+    EXPECT_EQ(proto.entry(0).transactions(0).layer_changes(1).z(), 43);
 }
 } // namespace android