Add 1.32x faster C implementation of asyncio.isfuture().

[jimmylai]

BPO	33521
Nosy	@pitrou, @vstinner, @asvetlov, @1st1, @jimmylai
PRs	bpo-33521: Add 1.32x faster C implementation of asyncio.isfuture(). #6876
Files	isfuture_benchmark.py isfuture_benchmark2.py

^{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 = None
created_at = <Date 2018-05-15.15:31:32.301>
labels = ['expert-asyncio', '3.8', 'performance']
title = 'Add 1.32x faster C implementation of asyncio.isfuture().'
updated_at = <Date 2018-05-26.00:14:20.203>
user = 'https://github.com/jimmylai'

bugs.python.org fields:

activity = <Date 2018-05-26.00:14:20.203>
actor = 'yselivanov'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['asyncio']
creation = <Date 2018-05-15.15:31:32.301>
creator = 'jimmylai'
dependencies = []
files = ['47593', '47603']
hgrepos = []
issue_num = 33521
keywords = ['patch']
message_count = 12.0
messages = ['316670', '316712', '317065', '317129', '317130', '317131', '317132', '317146', '317282', '317693', '317721', '317722']
nosy_count = 5.0
nosy_names = ['pitrou', 'vstinner', 'asvetlov', 'yselivanov', 'jimmylai']
pr_nums = ['6876']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue33521'
versions = ['Python 3.8']

[jimmylai]

asyncio.isfuture called whenever ensure_future is called. Providing C implementation to make it fast.

[jimmylai]

$./python.exe isfuture_benchmark.py -o isfuture_optimized.json
$ ./python.exe -m perf compare_to isfuture_original.json isfuture_optimized.json
Mean +- std dev: [isfuture_original] 7.16 ms +- 0.23 ms -> [isfuture_optimized] 5.41 ms +- 0.25 ms: 1.32x faster (-24%)

[vstinner]

About the benchmark: you should not loop inside the function. I propose a variant of the benchmark: isfuture_benchmark2.py.

Jimmy: Would you mind to run this variant on your PR?

[jimmylai]

@vstinner Thanks for the new benchmark, it provides more detailed wins:
It's 1.64x faster for future object and 1.23x faster for non-future object.
$ ./python.exe -m perf compare_to isfuture_original_2.json isfuture_optimized_2.json
future: Mean +- std dev: [isfuture_original_2] 224 ns +- 8 ns -> [isfuture_optimized_2] 135 ns +- 2 ns: 1.66x faster (-40%)
task: Mean +- std dev: [isfuture_original_2] 224 ns +- 6 ns -> [isfuture_optimized_2] 137 ns +- 3 ns: 1.64x faster (-39%)
regular_func: Mean +- std dev: [isfuture_original_2] 443 ns +- 5 ns -> [isfuture_optimized_2] 361 ns +- 5 ns: 1.23x faster (-18%)
str: Mean +- std dev: [isfuture_original_2] 449 ns +- 15 ns -> [isfuture_optimized_2] 360 ns +- 12 ns: 1.25x faster (-20%)

[pitrou]

What is the impact on a regular application? The fact that a micro-benchmark becomes X% faster isn't very interesting itself, especially as the original function, at less than 1µs per call, is already very fast.

[jimmylai]

@pitrou This change is part of optimization for asyncio.gather().
gather -> ensure_future -> isfuture/iscoroutine/isawaitable

We need C implementation for all those function to make gather really efficient for large scale application (e.g. Instagram)
Gather is really slow and cost ~2% CPU on our server.

The same optimization approach has been apply on other ciritcal asyncio modules, e.g. Future, get_event_loop, etc.

[pitrou]

Then it would be nice to post benchmarks using asyncio.gather() (on something not too trivial perhaps).

[jimmylai]

@pitrou We'll measure the wins of gather when we implement it in C. Before that, we need to get all helpers ready in C.

[vstinner]

@pitrou We'll measure the wins of gather when we implement it in C. Before that, we need to get all helpers ready in C.

You don't have to provide _asyncio.isfuture() (in C) to implement gather() in C.

If your goal is to optimize gather(), write a change to only implement gather() no?

What's the point of optimizing isfuture() is gather() is implemented in C and doesn't call the Python implementation anymore?

Implement isfuture() is C and expose it as _asyncio.isfuture() are two different things.