sync: use WakeList in Notify and batch_semaphore
#4071
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This commit updates `tokio::sync::Notify` to use the `WakeList` type added in PR #4055. This may improve performance somewhat, as it will avoid initializing a bunch of empty `Option`s when waking. I'd like to make similar changes to `BatchSemaphore`, but this is a somewhat larger change, as the wakers stored in the array are not `Waker`s but an internal type, and permit assigning operations are performed prior to waking.
This commit updates the internal semaphore implementation (`batch_semaphore.rs`) to use the new `WakeList` type added in PR #4055.
Darksonn
reviewed
Aug 25, 2021
tokio/src/util/mod.rs
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| #[cfg(any(feature = "io-driver", feature = "sync"))] | ||
| mod wake_list; | ||
| #[cfg(any(feature = "io-driver", feature = "sync"))] | ||
| pub(crate) use wake_list::WakeList; |
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Using feature = "io-driver" is incorrect. See the macro definition:
Lines 64 to 80 in 80bda3b
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agh, whoops --- thanks for catching that
Signed-off-by: Eliza Weisman <[email protected]>
Darksonn
approved these changes
Aug 25, 2021
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Motivation
PR #4055 added a new
WakeListtype, to manage a potentiallyuninitialized array when waking batches of wakers. This has the
advantage of not initializing a bunch of empty
Options when only asmall number of tasks are being woken, potentially improving performance
in these cases.
Currently,
WakeListis used only in the IO driver. However,tokio::synccontains some code that's almost identical to the code inthe IO driver that was replaced with
WakeList, so we can apply thesame optimizations there.
Solution
This branch changes
tokio::sync::Notifyandtokio::sync::batch_semaphore::Semaphoreto useWakeListwhen wakingbatches of wakers. This was a pretty straightforward drop-in
replacement.