[6.0] Fix quadratic performance of the ListMerger in specific usage pattern #74112
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…age pattern" This reverts commit 2640ff6.
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@swift-ci please test |
ktoso
added
performance
concurrency
DougGregor
approved these changes
Jun 4, 2024
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Thanks again for the great work here @nickolas-pohilets, we managed to get it back to 6.0 :-) |
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Description: Default actors used to use a ListMerger to manage the items and their priority in the queue; Under contention, this list merging was causing very noticeable performance degradation. Instead this PR introduces a new priority queue which manages a number of independent queues for each priority, removing the need for the "merging".
Scope/Impact: Impacts all default actor implementations.
Risk: Moderate, the change affects all default actors but has been thoroughly tested and reviewed by multiple people.
Testing: CI testing.
Reviewed by: @ktoso @rjmccall @mikeash
Original PR: #73998 (originally #70910)
Radar: rdar://114953765