The way to benchmark multithreaded actions.

Consider some object, which should hold a lot of concurrent operations at the same time.
There is the need to benchmark one operation from one thread (still having others working) to verify productivity during parallel load.
The problem is how to correctly hold that background threads still measuring one needed.

I see some ways, but none of them are completely possible now.
1. An ability to run benchmark methods in parallel, so every thread runs its own measuring still providing the needed concurrency.
2. Establish background in setup method. Unfortunatly, there is a need of "unsetup" method, where threads should be stopped.