GpuMem perfetto producer

To overcome the problem of ftrace gpumem events not emitting anything
during MEC (with apps that do launch-time allocations), this change adds
a perfetto producer to emit initial counter values at the start of a
trace, so that the visualization won't so zero usage.

Test: adb shell perfetto --query | grep gpu.
Test: Take a perfetto trace with android.gpumem enabled
Bug: 157142645
Change-Id: I5c8278754549399ffa51e6e6fc2ca69b51976cb2
diff --git a/services/gpuservice/tracing/GpuMemTracer.cpp b/services/gpuservice/tracing/GpuMemTracer.cpp
new file mode 100644
index 0000000..c9bfa57
--- /dev/null
+++ b/services/gpuservice/tracing/GpuMemTracer.cpp
@@ -0,0 +1,101 @@
+/*
+ * Copyright 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#undef LOG_TAG
+#define LOG_TAG "GpuMemTracer"
+#define ATRACE_TAG ATRACE_TAG_GRAPHICS
+
+#include "tracing/GpuMemTracer.h"
+
+#include <gpumem/GpuMem.h>
+#include <perfetto/trace/android/gpu_mem_event.pbzero.h>
+#include <unistd.h>
+#include <utils/Timers.h>
+
+#include <algorithm>
+#include <thread>
+
+PERFETTO_DEFINE_DATA_SOURCE_STATIC_MEMBERS(android::GpuMemTracer::GpuMemDataSource);
+
+namespace android {
+
+std::mutex GpuMemTracer::sTraceMutex;
+std::condition_variable GpuMemTracer::sCondition;
+bool GpuMemTracer::sTraceStarted;
+
+void GpuMemTracer::initialize(std::shared_ptr<GpuMem> gpuMem) {
+    if (!gpuMem->isInitialized()) {
+        ALOGE("Cannot initialize GpuMemTracer before GpuMem");
+        return;
+    }
+    mGpuMem = gpuMem;
+    perfetto::TracingInitArgs args;
+    args.backends = perfetto::kSystemBackend;
+    // TODO(b/160016498): Find a better way to wait for traced
+    // Sleep for 30 seconds to make sure the data source is registered only
+    // after traced starts.
+    sleep(30);
+    perfetto::Tracing::Initialize(args);
+    registerDataSource();
+    std::thread tracerThread(&GpuMemTracer::threadLoop, this);
+    pthread_setname_np(tracerThread.native_handle(), "GpuMemTracerThread");
+    tracerThread.detach();
+}
+
+void GpuMemTracer::registerDataSource() {
+    perfetto::DataSourceDescriptor dsd;
+    dsd.set_name(kGpuMemDataSource);
+    GpuMemDataSource::Register(dsd);
+}
+
+void GpuMemTracer::threadLoop() {
+    while (true) {
+        {
+            std::unique_lock<std::mutex> lock(GpuMemTracer::sTraceMutex);
+            while (!sTraceStarted) {
+                sCondition.wait(lock);
+            }
+        }
+        traceInitialCounters();
+        {
+            std::lock_guard<std::mutex> lock(GpuMemTracer::sTraceMutex);
+            sTraceStarted = false;
+        }
+    }
+}
+
+void GpuMemTracer::traceInitialCounters() {
+    if (!mGpuMem->isInitialized()) {
+        // This should never happen.
+        ALOGE("Cannot trace without GpuMem initialization");
+        return;
+    }
+    mGpuMem->traceGpuMemTotals([](uint32_t gpuId, uint32_t pid, uint64_t size) {
+        GpuMemDataSource::Trace([&](GpuMemDataSource::TraceContext ctx) {
+            auto packet = ctx.NewTracePacket();
+            packet->set_timestamp(systemTime());
+            auto* event = packet->set_gpu_mem_total_event();
+            event->set_gpu_id(gpuId);
+            event->set_pid(pid);
+            event->set_size(size);
+        });
+    });
+    // Flush the TraceContext. The last packet in the above loop will go
+    // missing without this flush.
+    GpuMemDataSource::Trace([](GpuMemDataSource::TraceContext ctx) { ctx.Flush(); });
+}
+
+} // namespace android