1 /*
2 * Copyright (C) 2022 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 // This example demonstrates startup tracing with a custom data source.
18 // Startup tracing can work only with kSystemBackend. Before running
19 // this example, `traced` must already be running in a separate process.
20
21 // Run system tracing: ninja -C out/default/ traced && ./out/default/traced
22 // And then run this example: ninja -C out/default example_startup_trace &&
23 // ./out/default/example_startup_trace
24
25 #if defined(PERFETTO_SDK_EXAMPLE_USE_INTERNAL_HEADERS)
26 #include "perfetto/tracing.h"
27 #include "perfetto/tracing/core/data_source_descriptor.h"
28 #include "perfetto/tracing/core/trace_config.h"
29 #include "perfetto/tracing/data_source.h"
30 #include "perfetto/tracing/tracing.h"
31 #include "protos/perfetto/trace/test_event.pbzero.h"
32 #else
33 #include <perfetto.h>
34 #endif
35
36 #include <fstream>
37 #include <iostream>
38 #include <thread>
39
40 namespace {
41
42 // The definition of our custom data source. Instances of this class will be
43 // automatically created and destroyed by Perfetto.
44 class CustomDataSource : public perfetto::DataSource<CustomDataSource> {};
45
InitializePerfetto()46 void InitializePerfetto() {
47 perfetto::TracingInitArgs args;
48 // The backends determine where trace events are recorded. For this example we
49 // are going to use the system-wide tracing service, because the in-process
50 // backend doesn't support startup tracing.
51 args.backends = perfetto::kSystemBackend;
52 perfetto::Tracing::Initialize(args);
53
54 // Register our custom data source. Only the name is required, but other
55 // properties can be advertised too.
56 perfetto::DataSourceDescriptor dsd;
57 dsd.set_name("com.example.startup_trace");
58 CustomDataSource::Register(dsd);
59 }
60
61 // The trace config defines which types of data sources are enabled for
62 // recording.
GetTraceConfig()63 perfetto::TraceConfig GetTraceConfig() {
64 perfetto::TraceConfig cfg;
65 cfg.add_buffers()->set_size_kb(1024);
66 auto* ds_cfg = cfg.add_data_sources()->mutable_config();
67 ds_cfg->set_name("com.example.startup_trace");
68 return cfg;
69 }
70
StartStartupTracing()71 void StartStartupTracing() {
72 perfetto::Tracing::SetupStartupTracingOpts args;
73 args.backend = perfetto::kSystemBackend;
74 perfetto::Tracing::SetupStartupTracingBlocking(GetTraceConfig(), args);
75 }
76
StartTracing()77 std::unique_ptr<perfetto::TracingSession> StartTracing() {
78 auto tracing_session = perfetto::Tracing::NewTrace();
79 tracing_session->Setup(GetTraceConfig());
80 tracing_session->StartBlocking();
81 return tracing_session;
82 }
83
StopTracing(std::unique_ptr<perfetto::TracingSession> tracing_session)84 void StopTracing(std::unique_ptr<perfetto::TracingSession> tracing_session) {
85 // Flush to make sure the last written event ends up in the trace.
86 CustomDataSource::Trace(
87 [](CustomDataSource::TraceContext ctx) { ctx.Flush(); });
88
89 // Stop tracing and read the trace data.
90 tracing_session->StopBlocking();
91 std::vector<char> trace_data(tracing_session->ReadTraceBlocking());
92
93 // Write the result into a file.
94 // Note: To save memory with longer traces, you can tell Perfetto to write
95 // directly into a file by passing a file descriptor into Setup() above.
96 std::ofstream output;
97 const char* filename = "example_startup_trace.pftrace";
98 output.open(filename, std::ios::out | std::ios::binary);
99 output.write(trace_data.data(),
100 static_cast<std::streamsize>(trace_data.size()));
101 output.close();
102 PERFETTO_LOG(
103 "Trace written in %s file. To read this trace in "
104 "text form, run `./tools/traceconv text %s`",
105 filename, filename);
106 }
107
108 } // namespace
109
110 PERFETTO_DECLARE_DATA_SOURCE_STATIC_MEMBERS(CustomDataSource);
111 PERFETTO_DEFINE_DATA_SOURCE_STATIC_MEMBERS(CustomDataSource);
112
main(int,const char **)113 int main(int, const char**) {
114 InitializePerfetto();
115
116 StartStartupTracing();
117
118 // Write an event using our custom data source before starting tracing
119 // session.
120 CustomDataSource::Trace([](CustomDataSource::TraceContext ctx) {
121 auto packet = ctx.NewTracePacket();
122 packet->set_timestamp(41);
123 packet->set_for_testing()->set_str("Startup Event");
124 });
125
126 auto tracing_session = StartTracing();
127
128 // Write an event using our custom data source.
129 CustomDataSource::Trace([](CustomDataSource::TraceContext ctx) {
130 auto packet = ctx.NewTracePacket();
131 packet->set_timestamp(42);
132 packet->set_for_testing()->set_str("Main Event");
133 });
134 StopTracing(std::move(tracing_session));
135
136 return 0;
137 }
138