[randomSamplingPercentage tracing policy] Controls the rate at which traffic will be selected for tracing if no prior sampling decision has been made. If a prior sampling decision has been made, that decision will be respected. However, if no sampling decision has been made (example: no
https://istio.io/latest/docs/reference/config/telemetry/x-b3-sampledtracing header was present in the requests), the traffic will be selected for telemetry generation at the percentage specified.
[sampling global setting sets] The percentage of requests (0.0 – 100.0) that will be randomly selected for trace generation, if not requested by the client or not forced. Default is 1.0.
https://istio.io/latest/docs/reference/config/istio.mesh.v1alpha1/
Daniel Velasco (notes?) 