I played a bit with the option "-n [NUM_CPUS]" in pytest (e.g., pytest -n 3 ...) and noticed a significant speedup. Unfortunately, for some reason that is still unclear to me, it looks like the JS engine processes are not properly killed. For example, after 5m of execution (with 3 out of 4 CPUs in use), I have seen more than 8 JS engines active (with top). Check what could be the reason for those "persistent processes".
I played a bit with the option "-n [NUM_CPUS]" in pytest (e.g., pytest -n 3 ...) and noticed a significant speedup. Unfortunately, for some reason that is still unclear to me, it looks like the JS engine processes are not properly killed. For example, after 5m of execution (with 3 out of 4 CPUs in use), I have seen more than 8 JS engines active (with top). Check what could be the reason for those "persistent processes".