Bug 698818 reports that Flash may be leaking and causing responsiveness issues. Firefox knows which subprocess corresponds to which plugin, seems like it shouldn't be too hard (?) to periodically sample the subprocess size and report it via telemetry. That will give us some hard data on plugin memory consumption, and the ability to monitor that over time. (EG, if a new Flash release suddenly makes things better/worse) I think we already report this for Firefox itself ("MEMORY_RESIDENT"?). Might be easy enough to hook that code up in the plugin children and report it periodically to the parent?

Bug 648415 is related -- it's open for including the plugin process in about:memory.

Chris, do you know if we care about this currently? Or can we close this for now?

Thanks for unearthing this bug, Georg. I think we can WONTFIX this bug because, AFAIK, we don't have any current plans to add telemetry for the plugin process's memory usage.