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/*
* Copyright (C) 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.
*/
// This example demonstrates in-process tracing with Perfetto.
#include "trace_categories.h"
#include <chrono>
#include <fstream>
#include <thread>
void InitializePerfetto() {
perfetto::TracingInitArgs args;
// The backends determine where trace events are recorded. For this example we
// are going to use the in-process tracing service, which only includes in-app
// events.
args.backends = perfetto::kInProcessBackend;
perfetto::Tracing::Initialize(args);
perfetto::TrackEvent::Register();
}
std::unique_ptr<perfetto::TracingSession> StartTracing() {
// The trace config defines which types of data sources are enabled for
// recording. In this example we just need the "track_event" data source,
// which corresponds to the TRACE_EVENT trace points.
perfetto::TraceConfig cfg;
cfg.add_buffers()->set_size_kb(1024);
auto* ds_cfg = cfg.add_data_sources()->mutable_config();
ds_cfg->set_name("track_event");
auto tracing_session = perfetto::Tracing::NewTrace();
tracing_session->Setup(cfg);
tracing_session->StartBlocking();
return tracing_session;
}
void StopTracing(std::unique_ptr<perfetto::TracingSession> tracing_session) {
// Make sure the last event is closed for this example.
perfetto::TrackEvent::Flush();
// Stop tracing and read the trace data.
tracing_session->StopBlocking();
std::vector<char> trace_data(tracing_session->ReadTraceBlocking());
// Write the result into a file.
// Note: To save memory with longer traces, you can tell Perfetto to write
// directly into a file by passing a file descriptor into Setup() above.
std::ofstream output;
output.open("example.pftrace", std::ios::out | std::ios::binary);
output.write(&trace_data[0], trace_data.size());
output.close();
}
void DrawPlayer(int player_number) {
TRACE_EVENT("rendering", "DrawPlayer", "player_number", player_number);
// Sleep to simulate a long computation.
std::this_thread::sleep_for(std::chrono::milliseconds(500));
}
void DrawGame() {
// This is an example of an unscoped slice, which begins and ends at specific
// points (instead of at the end of the current block scope).
TRACE_EVENT_BEGIN("rendering", "DrawGame");
DrawPlayer(1);
DrawPlayer(2);
TRACE_EVENT_END("rendering");
// Record the rendering framerate as a counter sample.
TRACE_COUNTER("rendering", "Framerate", 120);
}
int main(int, const char**) {
InitializePerfetto();
auto tracing_session = StartTracing();
// Give a custom name for the traced process.
perfetto::ProcessTrack process_track = perfetto::ProcessTrack::Current();
perfetto::protos::gen::TrackDescriptor desc = process_track.Serialize();
desc.mutable_process()->set_process_name("Example");
perfetto::TrackEvent::SetTrackDescriptor(process_track, desc);
// Simulate some work that emits trace events.
DrawGame();
StopTracing(std::move(tracing_session));
return 0;
}