Fast path ExecutionContext.Default for AsyncLocal #8227
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Can you share measurements? |
| { | ||
| ExecutionContext current = Thread.CurrentThread.ExecutionContext; | ||
| if (current == null) | ||
| ExecutionContext current = Thread.CurrentThread.ExecutionContext ?? ExecutionContext.Default; |
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This is always going to make things slower.
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Seems like the only case it could help is accessing AsyncLocal.Value when no values have been set, in which case it'll add the branch but save an interface method call.
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| if (newValue == null && newValues.Count == 0) | ||
| { | ||
| // Async locals cleared - set ExecutionContext back to Default to move back to fast-path |
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How likely is it that the async locals are ever cleared? It feels like a rare corner case.
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This would happen if all AsyncLocals in use were with T == reference types and all of them had their value set back to null (any T == value type in existence or any reference type not being set back to null would thwart this). I agree that does seem relatively rare.
| if (newValue == null && newValues.Count == 0) | ||
| { | ||
| // Async locals cleared - set ExecutionContext back to Default to move back to fast-path | ||
| Thread.CurrentThread.ExecutionContext = ExecutionContext.Default; |
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ExecutionContext contains more than just the async locals. Do you also need to compare the rest of the state?
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@benaadams have you had a chance to progress on this one? |
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It needs a deep dive; will close and come back when have something with results 😄 |
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Move back to Default ExecutionContext when AsyncLocals are cleared
Early exit if setting value to null on DefaultContext
Return
nullfor get if context is default without checking./cc @stephentoub @jkotas