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1# Perfetto trace config
2
3*** note
4**This doc is WIP**, stay tuned.
5<!-- TODO(primiano): write trace config doc. -->
6***
7
8![Trace Config](https://storage.googleapis.com/perfetto/markdown_img/trace-config.png)
9
10The [`TraceConfig`](/protos/perfetto/config/trace_config.proto) is an extensible
11protobuf message, sent by the consumer to the service, that defines:
12- The number and size of the trace buffer.
13- The duration of the trace.
14- [optionally] a file descriptor for the output trace and a periodic write
15  interval. If omitted the trace is kept only in memory.
16- The producers involved in the trace session.
17- The data sources involved in the trace session.
18- The configuration of each data source.
19- The crossbar mapping between each data source and the trace buffers.
20
21Each data source can create its own specialized schema for the config, like
22[this](/protos/perfetto/config/ftrace/ftrace_config.proto)
23
24See [`trace_config.proto`](/protos/perfetto/config/trace_config.proto) for more
25details.
26
27For convenience, a vulcanized trace config where all the nested protobuf
28sub-message definitions are squashed together is available in
29[`perfetto_config.proto`](/protos/perfetto/config/perfetto_config.proto).
30
31
32Specifying a custom trace config
33--------------------------------
34```bash
35cat > /tmp/config.txpb <<EOF
36# This is a text-encoded protobuf for /protos/perfetto/config/trace_config.proto
37duration_ms: 10000
38
39# For long traces set the following variables. It will periodically drain the
40# trace buffers into the output file, allowing to save a trace larger than the
41# buffer size.
42write_into_file: true
43file_write_period_ms: 5000
44
45buffers {
46  size_kb: 10240
47}
48
49data_sources {
50  config {
51    name: "linux.ftrace"
52    target_buffer: 0
53    ftrace_config {
54      buffer_size_kb: 40 # Kernel ftrace buffer size.
55      ftrace_events: "sched_switch"
56      ftrace_events: "print"
57    }
58  }
59}
60
61data_sources {
62  config {
63    name: "linux.process_stats"
64    target_buffer: 0
65  }
66}
67EOF
68
69protoc=$(pwd)/out/android/gcc_like_host/protoc
70
71$protoc --encode=perfetto.protos.TraceConfig \
72        -I$(pwd)/external/perfetto/protos \
73        $(pwd)/external/perfetto/protos/perfetto/config/perfetto_config.proto \
74        < /tmp/config.txpb \
75        > /tmp/config.pb
76
77cat /tmp/config.pb | adb shell perfetto -c - -o /data/misc/perfetto-traces/trace.pb
78adb shell cat /data/misc/perfetto-traces/trace.pb > /tmp/trace.pb
79out/android/trace_to_text json < /tmp/trace.pb > /tmp/trace.json
80
81# The file can now be viewed in chrome://tracing
82```
83