Revert "Reduce allocations due to resizing dictionaries" #12432
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This reverts commit 723c74e.
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Pull Request Overview
This PR reverts a previous optimization that attempted to reduce allocations by pre-sizing dictionaries in MSBuild's item collection system. The revert is necessary because the optimization was found to cause extra allocations in Visual Studio, contradicting its intended purpose.
Key changes:
- Removes capacity pre-allocation methods and their usage from item dictionary classes
- Simplifies property implementations by removing thread-safe wrappers where they were added for capacity tracking
- Eliminates EnsureCapacity calls from task execution and batching workflows
Reviewed Changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
src/Build/Collections/ItemDictionary.cs |
Removes Count/ItemTypesCount properties with locking and EnsureCapacity method |
src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs |
Removes EnsureCapacity calls before processing task outputs |
src/Build/BackEnd/Components/RequestBuilder/Lookup.cs |
Removes EnsureCapacity method and capacity-based constructor usage |
src/Build/BackEnd/Components/RequestBuilder/BatchingEngine.cs |
Removes EnsureCapacity call before adding items to buckets |
rainersigwald
approved these changes
Aug 26, 2025
baronfel
approved these changes
Aug 26, 2025
JanProvaznik
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Aug 27, 2025
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Reverts #12159
Confirmed with @Erarndt , it causes extra allocations in VS.