[layertracegenerator] stream layer trace to file

Write the generated layer trace entry by entry
so we don't hold the entire unserialized layer trace
in memory.

Fixes: 272158947
Test: presubmit
Test: open streamed trace in winscope
Test: cat /proc/`pidof layertracegenerator`/status
old
VmHWM:	  959496 kB
new
VmHWM:	   21416 kB

Change-Id: I4bf0cd8fe98d1e2a44fb6b7c85c4e06e586a52ed
diff --git a/services/surfaceflinger/Tracing/LayerTracing.cpp b/services/surfaceflinger/Tracing/LayerTracing.cpp
index 2918f7c..ecdeabe 100644
--- a/services/surfaceflinger/Tracing/LayerTracing.cpp
+++ b/services/surfaceflinger/Tracing/LayerTracing.cpp
@@ -18,6 +18,8 @@
 #define LOG_TAG "LayerTracing"
 #define ATRACE_TAG ATRACE_TAG_GRAPHICS
 
+#include <filesystem>
+
 #include <SurfaceFlinger.h>
 #include <android-base/stringprintf.h>
 #include <log/log.h>
@@ -44,30 +46,39 @@
     return true;
 }
 
-bool LayerTracing::disable(std::string filename) {
+bool LayerTracing::disable(std::string filename, bool writeToFile) {
     std::scoped_lock lock(mTraceLock);
     if (!mEnabled) {
         return false;
     }
     mEnabled = false;
-    LayersTraceFileProto fileProto = createTraceFileProto();
-    mBuffer->writeToFile(fileProto, filename);
+    if (writeToFile) {
+        LayersTraceFileProto fileProto = createTraceFileProto();
+        mBuffer->writeToFile(fileProto, filename);
+    }
     mBuffer->reset();
     return true;
 }
 
+void LayerTracing::appendToStream(std::ofstream& out) {
+    std::scoped_lock lock(mTraceLock);
+    LayersTraceFileProto fileProto = createTraceFileProto();
+    mBuffer->appendToStream(fileProto, out);
+    mBuffer->reset();
+}
+
 bool LayerTracing::isEnabled() const {
     std::scoped_lock lock(mTraceLock);
     return mEnabled;
 }
 
-status_t LayerTracing::writeToFile() {
+status_t LayerTracing::writeToFile(std::string filename) {
     std::scoped_lock lock(mTraceLock);
     if (!mEnabled) {
         return STATUS_OK;
     }
     LayersTraceFileProto fileProto = createTraceFileProto();
-    return mBuffer->writeToFile(fileProto, FILE_NAME);
+    return mBuffer->writeToFile(fileProto, filename);
 }
 
 void LayerTracing::setTraceFlags(uint32_t flags) {
diff --git a/services/surfaceflinger/Tracing/LayerTracing.h b/services/surfaceflinger/Tracing/LayerTracing.h
index 11bb9f4..40b0fbe 100644
--- a/services/surfaceflinger/Tracing/LayerTracing.h
+++ b/services/surfaceflinger/Tracing/LayerTracing.h
@@ -43,9 +43,10 @@
     LayerTracing();
     ~LayerTracing();
     bool enable();
-    bool disable(std::string filename = FILE_NAME);
+    bool disable(std::string filename = FILE_NAME, bool writeToFile = true);
+    void appendToStream(std::ofstream& out);
     bool isEnabled() const;
-    status_t writeToFile();
+    status_t writeToFile(std::string filename = FILE_NAME);
     static LayersTraceFileProto createTraceFileProto();
     void notify(bool visibleRegionDirty, int64_t time, int64_t vsyncId, LayersProto* layers,
                 std::string hwcDump, google::protobuf::RepeatedPtrField<DisplayProto>* displays);
diff --git a/services/surfaceflinger/Tracing/RingBuffer.h b/services/surfaceflinger/Tracing/RingBuffer.h
index 7e38c55..b41c65b 100644
--- a/services/surfaceflinger/Tracing/RingBuffer.h
+++ b/services/surfaceflinger/Tracing/RingBuffer.h
@@ -24,6 +24,7 @@
 #include <utils/Timers.h>
 #include <utils/Trace.h>
 #include <chrono>
+#include <fstream>
 #include <queue>
 
 namespace android {
@@ -73,6 +74,19 @@
         return NO_ERROR;
     }
 
+    status_t appendToStream(FileProto& fileProto, std::ofstream& out) {
+        ATRACE_CALL();
+        writeToProto(fileProto);
+        std::string output;
+        if (!fileProto.SerializeToString(&output)) {
+            ALOGE("Could not serialize proto.");
+            return UNKNOWN_ERROR;
+        }
+
+        out << output;
+        return NO_ERROR;
+    }
+
     std::vector<std::string> emplace(std::string&& serializedProto) {
         std::vector<std::string> replacedEntries;
         size_t protoSize = static_cast<size_t>(serializedProto.size());
diff --git a/services/surfaceflinger/Tracing/tools/LayerTraceGenerator.cpp b/services/surfaceflinger/Tracing/tools/LayerTraceGenerator.cpp
index 2418cf2..0ea421b 100644
--- a/services/surfaceflinger/Tracing/tools/LayerTraceGenerator.cpp
+++ b/services/surfaceflinger/Tracing/tools/LayerTraceGenerator.cpp
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#include <ios>
 #include <memory>
 #include <vector>
 #include "FrontEnd/LayerCreationArgs.h"
@@ -62,8 +63,11 @@
 
     LayerTracing layerTracing;
     layerTracing.setTraceFlags(LayerTracing::TRACE_INPUT | LayerTracing::TRACE_BUFFERS);
-    layerTracing.setBufferSize(512 * 1024 * 1024); // 512MB buffer size
+    // 10MB buffer size (large enough to hold a single entry)
+    layerTracing.setBufferSize(10 * 1024 * 1024);
     layerTracing.enable();
+    layerTracing.writeToFile(outputLayersTracePath);
+    std::ofstream out(outputLayersTracePath, std::ios::binary | std::ios::app);
 
     ALOGD("Generating %d transactions...", traceFile.entry_size());
     for (int i = 0; i < traceFile.entry_size(); i++) {
@@ -141,8 +145,10 @@
         auto displayProtos = LayerProtoHelper::writeDisplayInfoToProto(displayInfos);
         layerTracing.notify(visibleRegionsDirty, entry.elapsed_realtime_nanos(), entry.vsync_id(),
                             &layersProto, {}, &displayProtos);
+        layerTracing.appendToStream(out);
     }
-    layerTracing.disable(outputLayersTracePath);
+    layerTracing.disable("", /*writeToFile=*/false);
+    out.close();
     ALOGD("End of generating trace file. File written to %s", outputLayersTracePath);
     return true;
 }
diff --git a/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp b/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
index 74541ac..82aac7e 100644
--- a/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
+++ b/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
@@ -21,8 +21,10 @@
 #include <cstdint>
 #include "Client.h"
 
+#include <layerproto/LayerProtoHeader.h>
 #include "FrontEnd/LayerCreationArgs.h"
 #include "FrontEnd/Update.h"
+#include "Tracing/LayerTracing.h"
 #include "Tracing/RingBuffer.h"
 #include "Tracing/TransactionTracing.h"
 
@@ -305,4 +307,24 @@
     EXPECT_EQ(proto.entry(0).transactions(0).layer_changes().size(), 2);
     EXPECT_EQ(proto.entry(0).transactions(0).layer_changes(1).z(), 43);
 }
+
+// Verify we can write the layers traces by entry to reduce mem pressure
+// on the system when generating large traces.
+TEST(LayerTraceTest, canStreamLayersTrace) {
+    LayersTraceFileProto inProto = LayerTracing::createTraceFileProto();
+    inProto.add_entry();
+    inProto.add_entry();
+
+    std::string output;
+    inProto.SerializeToString(&output);
+    LayersTraceFileProto inProto2 = LayerTracing::createTraceFileProto();
+    inProto2.add_entry();
+    std::string output2;
+    inProto2.SerializeToString(&output2);
+
+    LayersTraceFileProto outProto;
+    outProto.ParseFromString(output + output2);
+    // magic?
+    EXPECT_EQ(outProto.entry().size(), 3);
+}
 } // namespace android