I suggest to use my perf module to run benchmark, especially if the tested function takes less than 1 ms, which is the case here.

Attached benchmark script calls asyncio.get_event_loop(). Result on the master branch with PR 3347:

haypo@selma$ ./python ~/bench_asyncio.py --inherit=PYTHONPATH -o patch.json
haypo@selma$ ./python ~/bench_asyncio.py --inherit=PYTHONPATH -o ref.json
haypo@selma$ ./python -m perf compare_to ref.json patch.json 

Mean +- std dev: [ref] 881 ns +- 42 ns -> [patch] 859 ns +- 14 ns: 1.03x faster (-3%)

I'm not convinced that the PR is worth it. 3% is not interesting on a micro benchmark.

Or is there an issue in my benchmark?