| # Perfetto trace format |
| |
| *** note |
| **This doc is WIP**, stay tuned. |
| <!-- TODO(primiano): write trace format doc. --> |
| *** |
| |
| A Perfetto trace is guaranteed to be a a linear sequence of `TracePacket(s)` |
| (see [trace_packet.proto](/protos/perfetto/trace/trace_packet.proto)). |
| |
| As a key part of the Perfetto design, the tracing service is agnostic of the |
| content of TracePacket, modulo the few fields defined in |
| [trusted_packet.proto](/protos/perfetto/trace/trusted_packet.proto) that are |
| produced by the service itself. |
| |
| Each data source can extend the trace with their app-specific protobuf schema. |
| *** aside |
| TODO(primiano): we should reserve an extension range and figure out / comment a |
| hash to assign sub-message IDs, even without checking them into |
| trace_packet.proto. |
| *** |
| |
| |
| **Linearity guarantees** |
| The tracing service guarantees that all `TracePacket(s)` written by a given |
| `TraceWriter` are seen in-order, without gaps or duplicates. If, for any reason, |
| a `TraceWriter` sequence becomes invalid, no more packets are returned to the |
| Consumer (or written into the trace file). |
| |
| However, `TracePacket(s)` written by different `TraceWriter` (hence even |
| different producers) can be seen in no particular order. |
| The consumer can re-establish a total order, if interested, using the packet |
| timestamps (after having synchronized the different clocks onto a global clock). |
