[issue42085] Add dedicated slot for sending values

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:

Oh, my bad. I can't find the enum values of the return type, though 
(PySendResult).

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[issue42085] Add dedicated slot for sending values

[Dennis Sweeney]

Dennis Sweeney  added the comment:

It did get added to the correct docs:

https://docs.python.org/3.10/c-api/typeobj.html#c.PyAsyncMethods.am_send

(the 3.10 and 3.11 docs, not the 3.9 docs ;-)

But as I mentioned, I feel that there could be more details about the 
semantics/contract.

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[issue42085] Add dedicated slot for sending values

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:

I am reopening this issue since am_send never got documented here: 
https://docs.python.org/3/c-api/typeobj.html#async-structs

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resolution: fixed -> 
status: closed -> open

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[issue42085] Add dedicated slot for sending values

[Dennis Sweeney]

Dennis Sweeney  added the comment:

Is there documentation anywhere for the semantics of am_send? I only see the 
signature followed by "See PyIter_Send for details", but the doc for 
PyIter_Send doesn't mention am_send.

In particular, it would be nice to document the relationship between 
PyIter_Send, am_send, and tp_iternext.

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[issue42085] Add dedicated slot for sending values

[Petr Viktorin]

Petr Viktorin  added the comment:

Py_TPFLAGS_HAVE_AM_SEND is unnecessary and I'd like to remove it.

It is not possible for type objects to have a different layout than the 
interpreter:
- extensions using the regular ABI must be recompiled for each feature version 
of Python
- extensions using the stable ABI can only create types dynamically

Or is there a different reason for Py_TPFLAGS_HAVE_AM_SEND? Checking it may be 
faster than ((Py_TYPE(x)->tp_as_async != NULL) && 
(Py_TYPE(x)->tp_as_async->am_send != NULL)), but I don't think the speedup is 
relevant.

See bpo-42747

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[issue42085] Add dedicated slot for sending values

[Irit Katriel]

Irit Katriel  added the comment:


New changeset d338ce0796e5fe8e54dfe52f93ed9d5936ad3efe by Miss Islington (bot) 
in branch '3.10':
bpo-42085: [docs] Add versionadded for am_send in type object documentation 
(GH-25465) (GH-26453)
https://github.com/python/cpython/commit/d338ce0796e5fe8e54dfe52f93ed9d5936ad3efe


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[issue42085] Add dedicated slot for sending values

[miss-islington]

Change by miss-islington :


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pull_request: https://github.com/python/cpython/pull/26453

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[issue42085] Add dedicated slot for sending values

[Irit Katriel]

Irit Katriel  added the comment:


New changeset 0b11c429c7f1721d9ffb9ae19e3e8e2e7bd6444d by Martmists in branch 
'main':
bpo-42085: [docs] Add versionadded for am_send in type object documentation 
(GH-25465)
https://github.com/python/cpython/commit/0b11c429c7f1721d9ffb9ae19e3e8e2e7bd6444d


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[issue42085] Add dedicated slot for sending values

[Martmists]

Change by Martmists :


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nosy_count: 4.0 -> 5.0
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pull_request: https://github.com/python/cpython/pull/25465

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[issue42085] Add dedicated slot for sending values

[Yury Selivanov]

Change by Yury Selivanov :


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resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue42085] Add dedicated slot for sending values

[Yury Selivanov]

Yury Selivanov  added the comment:

> Is anything left to do?

I think we can close this now.

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[issue42085] Add dedicated slot for sending values

[Andrew Svetlov]

Andrew Svetlov  added the comment:

Is anything left to do?

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[issue42085] Add dedicated slot for sending values

[STINNER Victor]

Change by STINNER Victor :


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[issue42085] Add dedicated slot for sending values

[miss-islington]

miss-islington  added the comment:


New changeset 7c9487ded487f304c2906698c52f0815b92cbeb6 by Vladimir Matveev in 
branch 'master':
bpo-42085: Add documentation for Py_TPFLAGS_HAVE_AM_SEND (GH-23374)
https://github.com/python/cpython/commit/7c9487ded487f304c2906698c52f0815b92cbeb6


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[issue42085] Add dedicated slot for sending values

[Vladimir Matveev]

Change by Vladimir Matveev :


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pull_request: https://github.com/python/cpython/pull/23374

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[issue42085] Add dedicated slot for sending values

[Andrew Svetlov]

Andrew Svetlov  added the comment:

Thank you Victor for the report!

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[issue42085] Add dedicated slot for sending values

[STINNER Victor]

STINNER Victor  added the comment:

commit cda99b4022daa08ac74b0420e9903cce883d91c6 (HEAD -> master, 
upstream/master)
Author: Andrew Svetlov 
Date:   Wed Nov 11 17:48:53 2020 +0200

Fix memory leak introduced by GH-22780 (GH-23237)

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[issue42085] Add dedicated slot for sending values

[STINNER Victor]

STINNER Victor  added the comment:

Thanks! The change fixed the leak:

$ ./python -m test -j0 -R 3:3 test_asyncgen test_coroutines test_unittest # 
test_asyncio 
(...)
Tests result: SUCCESS

I didn't run test_asyncio because the test is too slow.

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[issue42085] Add dedicated slot for sending values

[Andrew Svetlov]

Andrew Svetlov  added the comment:

PR for the fix is created: https://github.com/python/cpython/pull/23237

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[issue42085] Add dedicated slot for sending values

[Andrew Svetlov]

Change by Andrew Svetlov :


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[issue42085] Add dedicated slot for sending values

[Andrew Svetlov]

Andrew Svetlov  added the comment:

Investigating. The test leaks a future instance.

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[issue42085] Add dedicated slot for sending values

[STINNER Victor]

STINNER Victor  added the comment:

> New changeset 1e996c3a3b51e9c6f1f4cea8a6dbcf3bcb865060 by Vladimir Matveev in 
> branch 'master':

This change introduced big reference leaks:

4 tests failed:
test_asyncgen test_asyncio test_coroutines test_unittest

Example:

$ ./python -m test test_asyncgen -R 3:3 -m 
test.test_asyncgen.AsyncGenAsyncioTest.test_async_gen_asyncio_03
(...)
test_asyncgen leaked [63, 63, 63] references, sum=189
(...)

Please fix the leak, or revert if nobody is avaible to fix it:
https://pythondev.readthedocs.io/ci.html#revert-on-fail

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[issue42085] Add dedicated slot for sending values

[Yury Selivanov]

Yury Selivanov  added the comment:


New changeset 1e996c3a3b51e9c6f1f4cea8a6dbcf3bcb865060 by Vladimir Matveev in 
branch 'master':
bpo-42085: Introduce dedicated entry in PyAsyncMethods for sending values 
(#22780)
https://github.com/python/cpython/commit/1e996c3a3b51e9c6f1f4cea8a6dbcf3bcb865060


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[issue42085] Add dedicated slot for sending values

[Yury Selivanov]

Yury Selivanov  added the comment:

Vladimir, please do a follow up PR documenting Py_TPFLAGS_HAVE_AM_SEND.

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[issue42085] Add dedicated slot for sending values

[Terry J. Reedy]

Change by Terry J. Reedy :


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[issue42085] Add dedicated slot for sending values

[Vladimir Matveev]

Change by Vladimir Matveev :


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type:  -> performance

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[issue42085] Add dedicated slot for sending values

[Vladimir Matveev]

Change by Vladimir Matveev :


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pull_requests: +21739
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/22780

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[issue42085] Add dedicated slot for sending values

[Vladimir Matveev]

New submission from Vladimir Matveev :

https://bugs.python.org/issue41756 has introduced PyIter_Send as a common 
entrypoint for sending values however currently fast path that does not use 
StopIteration exception is only available for generators/coroutines. It would 
be quite nice if this machinery was extensible and other types (both internal 
and 3rd party) could opt-in into using exception-free way of returning values 
without needing to update the implementation of PyIter_Send. One way of solving 
this is adding a new slot with a signature that matches PyIter_Send. With it:
- it should be possible to implement this slot for coroutines/generators and 
remove  special casing for them  in PyIter_Send
- provide implementation for this slot for internal types (i.e. FutureIter in 
_asynciomodule.c) - results of this experiment can be found below
- enable external native extensions to provide efficient implementation of 
coroutines (i.e.  Cython could benefit from it)

Microbenchmark to demonstrate the difference of accessing the value of fulfiled 
Future without and with dedicated slot:
```
import asyncio
import time

N = 1

async def run():
fut = asyncio.Future()
fut.set_result(42)

t0 = time.time()
for _ in range(N):
await fut
t1 = time.time()
print(f"Time: {t1 - t0} s")

asyncio.run(run())
```
Time: 8.365560054779053 s - without the slot
Time: 5.799655914306641 s - with the  slot

--
components: Interpreter Core
messages: 378999
nosy: v2m
priority: normal
severity: normal
status: open
title: Add dedicated slot for sending values
versions: Python 3.10

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