Using Wasmtime's cross-platform profiler

The guest profiling strategy enables in-process sampling and will write the captured profile to a file which can be viewed at https://profiler.firefox.com/.

To use this profiler with the Wasmtime CLI, pass the --profile=guest[,path[,interval]] flag.

• path is where to write the profile, wasmtime-guest-profile.json by default
• interval is the duration between samples, 10ms by default

When used with -W timeout=N, the timeout will be rounded up to the nearest multiple of the profiling interval.

To use this profiler when embedding Wasmtime, see GuestProfiler. An embedder that profiles the same modules many times, for example once per instance, can prepare them once with GuestProfilerModules and start each profile with GuestProfiler::new_with_modules; wasmtime serve does this.