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 three files:
- A
.events
file which contains all of the traced events. - A
.string_data
file which contains all the strings referenced by events. - A
.string_index
file which mapsStringId
values to offsets into the.string_data
file.
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 eventevent_id
: a [StringId
] which specifies the name of the eventthread_id
: au32
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