This crate provides a library for high-performance event tracing which is used by
the Rust compiler's unstable `-Z self-profile` feature.
The output of a tracing session will be an `.mm_profdata` file containing a stream
of events and a string table that allows to decode the `StringId`s in the event stream.
# Writing event trace files
The main entry point for writing event trace files is the [`Profiler`] struct.
To create a [`Profiler`], call the [`Profiler::new()`] function and provide a `Path` with
the directory and file name for the trace files.
Alternatively, call the [`Profiler::with_counter()`] function, to choose the [`Counter`]
the profiler will use for events (whereas [`Profiler::new()`] defaults to `wall-time`).
For more information on available counters, see the [`counters`] module documentation.
To record an event, call the [`Profiler::record_instant_event()`] method, passing a few
arguments:
- `event_kind`: a [`StringId`] which assigns an arbitrary category to the event
- `event_id`: a [`StringId`] which specifies the name of the event
- `thread_id`: a `u32` id of the thread which is recording this event
Alternatively, events can also be recorded via the
[`Profiler::start_recording_interval_event()`] method. This method records a "start" event and
returns a `TimingGuard` object that will automatically record the corresponding "end" event
when it is dropped.
To create a [`StringId`], call one of the string allocation methods:
- [`Profiler::alloc_string()`]: allocates a string and returns the [`StringId`] that refers
to it
[`Counter`]: counters::Counter