detox is the distributed version of tox. It makes efficient use of multiple CPUs by running all possible activities in parallel. It has the same options and configuration that tox has so after installation can just run:
detox
in the same way and with the same options with which you would run tox, see the tox home page for more info.
Additionally, detox offers a -n or --num option to set the number of concurrent processes to use.
NOTE due to the concurrent execution of the testenvs the output of the different testruns is not printed to the termineal. Instead they are logged into separate files inside the log directories of the testenvs.