[issue35580] Windows IocpProactor: CreateIoCompletionPort 4th arg 0xffffffff -- why is this value the default?

Jeff Robbins added the comment: I don't understand why 0 would be safer. Since asyncio can only service this IOCP from its single threaded event loop, I would have thought 1 would express the intent better. Why not convey to the OS what we're up to, in case that helps it do a better job

[issue35580] Windows IocpProactor: CreateIoCompletionPort 4th arg 0xffffffff -- why is this value the default?

Andrew Svetlov added the comment: >From my understanding the question is: replace 0x with 0 or 1? I don't know much about IOCP, 0 sounds safer for me. -- ___ Python tracker

[issue35580] Windows IocpProactor: CreateIoCompletionPort 4th arg 0xffffffff -- why is this value the default?

STINNER Victor added the comment: > Am I correct that only one thread calls `GetQueuedCompletionStatus` on a > given `iocp` object in asyncio under Windows `IocpProactor`? An asyncio event loop must only run in a single thread at the same time. It doesn't make sense to run the same event

[issue35580] Windows IocpProactor: CreateIoCompletionPort 4th arg 0xffffffff -- why is this value the default?

Jeff Robbins added the comment: Per https://stackoverflow.com/questions/38133870/how-the-parameter-numberofconcurrentthreads-is-used-in-createiocompletionport, it seems that `NumberOfConcurrentThreads` controls what happens when multiple threads call `GetQueuedCompletionStatus`. But

[issue35580] Windows IocpProactor: CreateIoCompletionPort 4th arg 0xffffffff -- why is this value the default?

Andrew Svetlov added the comment: The value type is DWORD. 0x is a maximum allowed value for DWORD. 0 implies something like 8 for Intel i7. I don't remember the reason (the value was present is very first proactor implementation and never changed after it). Maybe giving Windows a

[issue35580] Windows IocpProactor: CreateIoCompletionPort 4th arg 0xffffffff -- why is this value the default?

New submission from Jeff Robbins : By default, the __init__ function of IocpProactor in windows_events.py calls CreateIoCompletionPort with a 4th argument of 0x, yet MSDN doesn't document this as a valid argument.