Fix an allocation regression due to the recent SegmentedList change c… #75895
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
…aught by speedometer The change in dotnet#75756 was incorrect when the existing number of items is between SegmentSize /2 and SegmentSize. In this case, the size of the newCapacity would end up as exactly the requested capacity, causing a potentially O(n^2) allocation growth pattern if caller was just increasing the requested capacity by one from it's current size. The fix is just to handle that case directly, and if the existing size falls into that range, to simply set the desired newCapacity to the SegmentSize.
dotnet-issue-labeler
bot
added
Area-Compilers
untriaged
sharwell
approved these changes
Nov 13, 2024
CyrusNajmabadi
approved these changes
Nov 13, 2024
jjonescz
approved these changes
Nov 13, 2024
3 tasks
This was referenced Nov 15, 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Outdated suggestions cannot be applied.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.
…aught by speedometer
The change in #75756 was incorrect when the existing number of items is between SegmentSize /2 (inclusive) and SegmentSize (exclusive). In this case, the size of the newCapacity would end up as exactly the requested capacity, causing a potentially O(n^2) allocation growth pattern if caller was just increasing the requested capacity by one from it's current size.
The fix is just to handle that case directly, and if the existing size falls into that range, to simply set the desired newCapacity to the SegmentSize.