Time Trace and Profiling

Use Google's Perfetto to visualize time traces, enabling simple profiling of your C++. Glaze writes out JSON traces conformant to Google's Trace Event Format.

The glz::trace class is entirely thread safe.

Glaze provides begin and end members for duration traces. Asynchronous traces use async_begin and async_end.

An example of the API in use:

#include "glaze/trace/trace.hpp"

glz::trace trace{}; // make a structure to store a trace

trace.begin("my event name");
// compute something here
trace.end("my event name");

auto ec = glz::write_file_json(trace, "trace.json", std::string{});

Or, for async events:

glz::trace trace{}; // make a structure to store a trace

trace.async_begin("my event name");
// compute something here
trace.async_end("my event name");

Args (metadata)

Glaze allows args as an additional argument to begin and end methods, which will provide metadata in Perfetto.

// arguments could be any type that can be serialized to JSON
trace.begin("my event name", arguments);
// do stuff
trace.end("my event name");

Example with a string:

trace.begin("my event name", "My event description");
// do stuff
trace.end("my event name");

Runtime Disabling Trace

trace.disabled = true; // no data will be collected

Compile Time Disabling Trace

A boolean template parameter Enabled defaults to true, but can be set to false to compile time disable tracing and thus remove the binary when compiled.

glz::trace<false> trace{};

When disabled, writing glz::trace as JSON will result in an empty JSON object: {}

Scoped Tracing

Automatically ends the event when it goes out of scope:

{
  auto scoper = trace.scope("event name"); // trace.begin("event name") called
  // run event
}
// end("event name") automatically called when leaving scope

Automatically ends the async event when it goes out of scope:

{
  auto scoper = trace.async_scope("event name"); // trace.async_begin("event name") called
  // run event
}
// trace.async_end("event name") automatically called when leaving scope

Global tracing

It can be bothersome to pass around a glz::trace instance. A global instance can be made for convenience:

inline glz::trace global_trace{};