Optimize asyncio.ensure_future by reordering if conditions

[jimmylai]

BPO	33505
Nosy	@asvetlov, @1st1, @jimmylai
PRs	bpo-33505: Optimize asyncio.ensure_future by reordering if conditions #6832 bpo-33505: Optimize asyncio.ensure_future by reordering if conditions #6836 [3.7] bpo-33505: Optimize asyncio.ensure_future by reordering if conditions (GH-6836) #7162
Files	ensure_future_benchmark.py: ./python.exe ensure_furture_benchmark.py -o ensure_future_optimized.json

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2018-05-28.19:14:26.685>
created_at = <Date 2018-05-14.20:45:32.923>
labels = ['3.8', 'expert-asyncio', '3.7', 'performance']
title = 'Optimize asyncio.ensure_future by reordering if conditions'
updated_at = <Date 2018-05-28.19:14:26.684>
user = 'https://github.com/jimmylai'

bugs.python.org fields:

activity = <Date 2018-05-28.19:14:26.684>
actor = 'yselivanov'
assignee = 'none'
closed = True
closed_date = <Date 2018-05-28.19:14:26.685>
closer = 'yselivanov'
components = ['asyncio']
creation = <Date 2018-05-14.20:45:32.923>
creator = 'jimmylai'
dependencies = []
files = ['47591']
hgrepos = []
issue_num = 33505
keywords = ['patch']
message_count = 4.0
messages = ['316572', '316656', '317887', '317899']
nosy_count = 3.0
nosy_names = ['asvetlov', 'yselivanov', 'jimmylai']
pr_nums = ['6832', '6836', '7162']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue33505'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']

[jimmylai]

ensure_future converts the input as future if it's not already a future.
The condition is the following:

if futures.isfuture(coro_or_future):
    ...
elif coroutines.iscoroutine(coro_or_future):
    ...
elif inspect.isawaitable(coro_or_future):
    ...

In real world, ensure_future is mostly called by run_until_complete and gather with async function call (coroutine) as input.
We should check iscoroutine first to make it most efficient.

[jimmylai]

Benchmark result:
./python.exe -m perf compare_to ensure_future_original.json ensure_future_optimized.json
Mean +- std dev: [ensure_future_original] 57.4 ms +- 4.0 ms -> [ensure_future_optimized] 49.3 ms +- 4.5 ms: 1.17x faster (-14%)

[1st1]

New changeset e549c4b by Yury Selivanov (jimmylai) in branch 'master':
bpo-33505: Optimize asyncio.ensure_future by reordering if conditions (GH-6836)
e549c4b

[1st1]

New changeset f8fdb36 by Yury Selivanov (Miss Islington (bot)) in branch '3.7':
bpo-33505: Optimize asyncio.ensure_future by reordering if conditions (GH-6836) (bpo-7162)
f8fdb36