trio.timeit utility

[belm0]

Trio should offer an async timeit utility. It's useful for measuring performance of "fast" async calls such as sleep(0).

It's important for both trio devs and users to understand the overhead of checkpoints. E.g. for users: in situations where you're quickly draining an async queue, or when you're deciding how frequently to call sleep(0) in some CPU bound loop.

Here's an example using the pytest harness. Ideally we'd have a module with the same API as timeit, only running within a trio async context.

async def test_sleep0_perf():
    n = 10
    dt = 0
    while True:
        t0 = perf_counter()
        for _ in range(n):
            await trio.sleep(0)
        dt = perf_counter() - t0
        if dt < 0.2:
            n *= 10
        else:
            break
    print(f'{1e6 * dt / n: .1f} usec average in {n} calls')
    assert False