New submission from Samuel Colvin: This is best described the script at https://gist.github.com/samuelcolvin/00f01793c118bf9aafae886ffbc81a58.
Basically, completing a set of tasks using asyncio.wait(...return_when=asyncio.FIRST_COMPLETED) in a loop to wait for them to finish is much much slower than completing the same set of tasks using just asyncio.wait(pending_tasks, loop=loop, return_when=asyncio.ALL_COMPLETED). In my example, the ALL_COMPLETED case takes ~5s, but the FIRST_COMPLETED case takes 18 - 47s. The screenshot on the gist shows network usage with a very long tail, in other words very few tasks are taking a long time to complete. This example uses aiohttp get a url as the test case but I'm pretty sure this isn't an issue with aiohttp. I tried the same thing with uvloop but got broadly the same result. ---------- components: asyncio files: asyncio_wait_test.py messages: 295045 nosy: samuelcolvin, yselivanov priority: normal severity: normal status: open title: asyncio.wait very slow with FIRST_COMPLETED type: performance versions: Python 3.6 Added file: http://bugs.python.org/file46920/asyncio_wait_test.py _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue30556> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
