Fix cross-AppDomain TaskItem modifier cache regression#13493
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DustinCampbell wants to merge 1 commit intomainfrom
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Fix cross-AppDomain TaskItem modifier cache regression#13493DustinCampbell wants to merge 1 commit intomainfrom
DustinCampbell wants to merge 1 commit intomainfrom
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Pull request overview
Fixes a .NET Framework Visual Studio allocation regression caused by copying an embedded modifier-cache struct across AppDomains by moving the cache onto the item objects themselves via an internal interface.
Changes:
- Replace
ItemSpecModifiers.Cachestruct with anIItemSpecModifierCacheinterface and update modifier computation to use it. - Implement per-item modifier caching directly on
TaskItem,ProjectItem,ProjectItemInstance.TaskItem, andTaskParameterTaskItem. - Refactor
ItemSpecModifiers.GetItemSpecModifierinto caching vs non-caching overloads and extract defining-project modifier resolution.
Reviewed changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| src/Utilities/TaskItem.cs | Moves derivable modifier caching onto TaskItem via IItemSpecModifierCache and clears cache on ItemSpec changes. |
| src/Shared/TaskParameter.cs | Updates TaskParameterTaskItem to use IItemSpecModifierCache for modifier caching. |
| src/Framework/ItemSpecModifiers.cs | Reworks modifier computation to support caching through IItemSpecModifierCache and adds a non-caching overload. |
| src/Framework/IItemSpecModifierCache.cs | Introduces internal interface for per-item derivable modifier caching across AppDomain boundaries. |
| src/Framework.UnitTests/FileUtilities_Tests.cs | Updates tests to use the new cache interface instead of the removed struct cache. |
| src/Build/Instance/ProjectItemInstance.cs | Implements cache interface on ProjectItemInstance.TaskItem, clears cache on spec changes, and copies cache on clone. |
| src/Build/Definition/ProjectItem.cs | Implements cache interface on ProjectItem and routes built-in metadata through the new cache API. |
| src/Build/Definition/BuiltInMetadata.cs | Switches built-in metadata APIs from ref Cache to IItemSpecModifierCache. |
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|
experimentally inserting to run speedometer at exp/dev/dustinca/fix-cross-appdomain-taskitem-cache branch (ETA results in 8h) |
Recently, ItemSpecModifiers.GetItemSpecModifier was changed to take a Cache struct rather than a single "string? fullPath" parameter. Unfortunately, this increases memory allocations to an unexpected degree -- especially in cross-AppDomain scenarios. This change reduces the size of the Cache struct to just a single FullPath field, which should remove the allocation regression.
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The ItemSpecModifiers.Cache struct I introduced with #13386 caused a surprising ~200 MB allocation regression in Visual Studio scenarios on .NET Framework. Essentially, when TaskItem (a MarshalByRefObject) cached modifiers in an embedded struct, there's a huge cost to copy that struct cross-AppDomain.
To fix the problem, reduce the Cache struct to just a single field to store the full path. This should effectively bring memory allocations back in line.