import asyncio
import time

def test(loop, iterations=10**4):
    loop._ready.clear()
    t0 = time.perf_counter()
    for x in range(iterations):
        loop.call_soon(str)
    dt = time.perf_counter() - t0
    loop._ready.clear()
    return dt / iterations

@asyncio.coroutine
def bench(loop, runs=5):
    yield from []
    perf = [test(loop) for run in range(runs)]
    best = min(perf)
    print("call_soon(): %.0f ns per call" % (best * 1e9))

loop = asyncio.get_event_loop()
loop.run_until_complete(bench(loop))
loop.close()