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 StringIds 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