At Perforator, we also started from Google's beautiful pprof, but then eliminated all nested repeated fields, converging to https://github.com/yandex/perforator/blob/main/perforator/pr.... Repeated fields in protobufs are really memory & CPU hungry.

This layout allows us to quickly merge hundreds of millions of samples into a single profile. The only practical limit is protobuf's 2GB message size cap.