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Avoid creating a yield ID counter per async writer #2768

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merged 4 commits into from
Jul 9, 2024
Merged

Avoid creating a yield ID counter per async writer #2768

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921a1ad
Avoid creating a yield ID counter per async writer
glbrntt Jul 5, 2024
95f909a
better naming
glbrntt Jul 8, 2024
0026472
Merge branch 'main' into shared-yield-id-generator
glbrntt Jul 8, 2024
2d77b0c
Merge branch 'main' into shared-yield-id-generator
glbrntt Jul 9, 2024
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8 changes: 4 additions & 4 deletions Sources/NIOCore/AsyncSequences/NIOAsyncWriter.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,9 @@ import DequeModule
import NIOConcurrencyHelpers
import _NIODataStructures

@usableFromInline
let yieldIDCounter = ManagedAtomic<UInt64>(0)
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This would probably be nicer as a static, but this is otherwise reasonable.

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Agreed but wasn't sure where to put it. The obvious place is NIOAsyncWriter but that's generic so can't have a static let.

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I am not sure if I agree with this move. I understand that we want to reduce allocations but IMO the correct move forward is to replace SwiftAtomics.ManagedAtomic with Synchronisation.Atomic which should avoid the allocation as well since it is ~Copyable. We ought to be able to do this conditionally when the compiler is Swift 6. Though availability might be tricky. If availability blocks us we can move this into a global. I would suggest renaming though to scope it better e.g. let _asyncWriterYieldIDCounter or something like that

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I agree re: using Synchronization.Atomic but as noted, the availability makes this difficult. I've renamed the global though.


/// The delegate of the ``NIOAsyncWriter``. It is the consumer of the yielded writes to the ``NIOAsyncWriter``.
/// Furthermore, the delegate gets informed when the ``NIOAsyncWriter`` terminated.
///
Expand Down Expand Up @@ -434,14 +437,11 @@ extension NIOAsyncWriter {
}
}

@usableFromInline
/* private */ internal let _yieldIDCounter = ManagedAtomic<UInt64>(0)

@inlinable
func generateUniqueYieldID() -> YieldID {
// Using relaxed is fine here since we do not need any strict ordering just a
// unique ID for every yield.
.init(value: self._yieldIDCounter.loadThenWrappingIncrement(ordering: .relaxed))
.init(value: yieldIDCounter.loadThenWrappingIncrement(ordering: .relaxed))
}
}

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