This CL introduces cppgc::HistogramRecorder api which is similar to the
v8::metrics::Recorder api and is used by cppgc to report histogram
samples to embedders. Embedders should implement the api if they want to
collect histograms and provide an instance of it on heap creation.
CppHeap uses an adaptor class that implements the HistogramRecorder api
and is used to forward the relevant info to the relevant
v8::metrics::Recorder.
The api used 3 data structures: 2 for incremental steps that need to be
reported as they come (marking and sweeping) and 1 for the end of a GC
cycle that aggregates statistics over the entire cycle.
The data structure only provide the "raw" samples (e.g. atomic mark
time, incremental mark time, etc...). The embedder is expected to
compute aggregate histogram on its own (e.g. overall marking time).
Bug: chromium:1056170
Change-Id: If63ef50a29a21594f654edb83084598980d221ce
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2642258
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72256}
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