From a recent internal discussion on #forum-pcp with folks using the /metrics endpoint to scrape PCP metrics, it would be handy to have the ability to cull certain metrics at the source (rather than sampling then transferring them across the wire to the client).

The pmwebapi(3) has a "names" parameter which restricts the full set of PCP metrics to those matching that value, this "filter" option would be the inverse - further reducing the set of metrics exported.