It’s using a great deal of cpu, and memory, and writing 10GB files. What is it?
From the man page:
NAME rtcreportingd — Diagnostics and Usage Reporting SYNOPSIS rtcreportingd DESCRIPTION rtcreportingd is a system daemon that collects diagnostics and usage telemetry data locally for users that have opted in for reporting. There are no configuration options to rtcreportingd, and users should not run rtcreportingd manually.
Interesting, so one of my apps must have turned it on… wonder how I can find out.
Check System Preferences/Privacy for the option to send diagnostic data to Apple.
I think this is the result of that button Apple asks you to click after updates, to send data to Apple to help improve things – not anything an app would do.