5.6: Fix SR-15785 by adding a cached reference to the last linked list node, avoiding n^2 append scaling #41192
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
…t node, avoiding n^2 append scaling
|
@swift-ci please nominate |
ktoso
approved these changes
Feb 3, 2022
|
@swift-ci please test |
|
@swift-ci please test windows platform |
DougGregor
approved these changes
Mar 23, 2022
|
@swift-ci please test macOS platform |
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Outdated suggestions cannot be applied.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.
Explanation: Adding children to a TaskGroup is currently n^2, which is causing severe performance issues for users of Swift Concurrency.
Scope: This change improves the performance of adding 50,000 children to a group from 10-15 seconds to less than 0.2 seconds. It costs one word of memory per child.
Radar/SR Issue: SR-15785
Risk: If I got the change wrong we could potentially see crashes or other misbehavior when using TaskGroups
Testing: Test suite passes, community provided benchmark shows expected improvement
Reviewer: @DougGregor (I think you're the Concurrency code owner? CODE_OWNERS doesn't list it)
Original PR: #41165