[6.0] Use an AtomicInt32 to count pendingUnitCount instead of using AsyncQueue
#1744
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
…yncQueue` Adding an item to `AsyncQueue<Serial>` is linear in the number of pending queue items, thus adding n items to an `AsyncQueue` before any can execute is in O(n^2). This decision was made intentionally because the primary use case for `AsyncQueue` was to track pending LSP requests, of which we don’t expect to have too many pending requests at any given time. `SourceKitIndexDelegate` was also using `AsyncQueue` to track the number of pending units to be processed and eg. after indexing SourceKit-LSP, I have seen this grow up to ~20,000. With the quadratic behavior, this explodes time-wise. Turns out that we don’t actually need to use a queue here at all, an atomic is sufficient and much faster. Independently, we should consider mitigating the quadratic behavior of `AsyncQueue<Serial>` or `AsyncQueue` in general. Fixes swiftlang#1541 rdar://130844901
|
@swift-ci Please test |
bnbarham
approved these changes
Oct 9, 2024
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
AsyncQueue<Serial>is linear in the number of pending queue items, thus adding n items to anAsyncQueuebefore any can execute is in O(n^2). This decision was made intentionally because the primary use case forAsyncQueuewas to track pending LSP requests, of which we don’t expect to have too many pending requests at any given time.SourceKitIndexDelegatewas also usingAsyncQueueto track the number of pending units to be processed and eg. after indexing SourceKit-LSP, I have seen this grow up to ~20,000. With the quadratic behavior, this explodes time-wise and also uses a bunch of memory for those tasks.Turns out that we don’t actually need to use a queue here at all, an atomic is sufficient and much faster.
AtomicInt32to countpendingUnitCountinstead of usingAsyncQueue#1720