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Pull request overview
This PR introduces a new MSBuild.Benchmarks project and refactors item-spec modifier evaluation/caching paths (ItemSpecModifiers, BuiltInMetadata, and item implementations) to significantly reduce repeated computation and allocations in common metadata-access scenarios.
Changes:
- Add
MSBuild.Benchmarks(BenchmarkDotNet-based) and wire it into solution files / ignore BenchmarkDotNet artifacts. - Replace single-string FullPath caching with a richer per-item
ItemSpecModifiers.Cache, plus a shared cache forDefiningProject*modifiers. - Refactor modifier identification to a fast length/character-based classifier (
ItemSpecModifierKind) and update call sites/tests accordingly.
Reviewed changes
Copilot reviewed 21 out of 22 changed files in this pull request and generated 8 comments.
Show a summary per file
| File | Description |
|---|---|
| src/Utilities/TaskItem.cs | Switch TaskItem built-in metadata caching from _fullPath to ItemSpecModifiers.Cache. |
| src/Shared/TaskParameter.cs | Update serialized task item metadata retrieval to use ItemSpecModifiers.Cache + kind-based lookup. |
| src/MSBuild.Benchmarks/readme.md | Add benchmark-running documentation. |
| src/MSBuild.Benchmarks/Program.cs | Add benchmark host with custom CLI flags and config wiring. |
| src/MSBuild.Benchmarks/MSBuild.Benchmarks.csproj | New benchmarks project with BenchmarkDotNet references and MSBuild project references. |
| src/MSBuild.Benchmarks/ItemSpecModifiersCachingBenchmark.cs | Add benchmarks focused on per-item caching behavior. |
| src/MSBuild.Benchmarks/ItemSpecModifiersBenchmark.cs | Add benchmarks for modifier classification and single-call modifier computation. |
| src/MSBuild.Benchmarks/Extensions.cs | Add helper extensions for BenchmarkDotNet summary exit codes. |
| src/MSBuild.Benchmarks/DefiningProjectModifiersBenchmark.cs | Add benchmarks for DefiningProject* modifier scenarios (single/multi project). |
| src/Framework/Properties/AssemblyInfo.cs | Add IVT for MSBuild.Benchmarks so it can access internal Framework APIs. |
| src/Framework/ItemSpecModifiers.cs | Major refactor: kind-based modifier classifier, per-item cache struct, and shared defining-project cache. |
| src/Framework/ItemSpecModifierKind.cs | Introduce enum for fast modifier-kind dispatch. |
| src/Framework.UnitTests/FileUtilities_Tests.cs | Update tests to new ItemSpecModifierKind/cache-based APIs. |
| src/Build/Instance/ProjectMetadataInstance.cs | Speed up reserved-name validation using ItemSpecModifiers.IsItemSpecModifier. |
| src/Build/Instance/ProjectItemInstance.cs | Update built-in metadata retrieval + caching to use ItemSpecModifierKind and ItemSpecModifiers.Cache. |
| src/Build/Evaluation/Expander.cs | Update %() transform path to call the new GetItemSpecModifier overload. |
| src/Build/Definition/ProjectItem.cs | Update built-in metadata retrieval/caching to ItemSpecModifiers.Cache. |
| src/Build/Definition/BuiltInMetadata.cs | Refactor built-in metadata access to kind-based dispatch and cache struct. |
| eng/dependabot/Directory.Packages.props | Update/add BenchmarkDotNet package versions for central management. |
| MSBuild.slnx | Add benchmarks project to the solution definition. |
| MSBuild.Dev.slnf | Add benchmarks project to the dev solution filter. |
| .gitignore | Ignore BenchmarkDotNet.Artifacts/ outputs. |
- Update BenchmarkDotNet to version: 0.13.12. - Add BenchmarkDotNet.Diagnostics.Windows package for capturing ETW traces. - Add project to contain benchmarks written against Microsoft.Build, Microsoft.Build.Framework, Microsoft.Build.Tasks, or Microsoft.Build.Utilities
- Add nullability annotations - Use string length and starting characters as discriminators to avoid hashing every modifier. - Reduce complexity of GetItemSpecModifier. - Don't call GetItemSpecModifier recursively for DefiningProject* modifiers.
Introduce CachedItemSpecModifiers struct to cache derivable modifier results (FullPath, RootDir, Filename, Extension, RelativeDir, Directory) per item, replacing the single fullPath cache. This eliminates redundant Path.GetFileNameWithoutExtension, Path.GetExtension, and similar calls across repeated metadata accesses on the same item.
DefiningProject* modifiers (FullPath, Directory, Name, Extension) operate on the defining project path, not the item spec. In a typical build there are only ~15 distinct defining projects but tens of thousands of items, so the same ComputeFullPath/ComputeRootDir/ComputeDirectory chain was running redundantly for every item. Add a ConcurrentDictionary<string, DefiningProjectModifierCache> keyed by the escaped defining project path. All four modifier values are computed eagerly on the first miss and shared across all items from that project. TryGetValue on the hot path avoids closure allocation; the GetOrAdd fallback runs only once per distinct project.
- Extract ModifierKind to a top-level internal enum (ItemSpecModifierKind) and make TryGetModifierKind public so callers can resolve the modifier name once and pass the kind through, eliminating redundant lookups. - Add TryGetDerivableModifierKind for the common pattern of resolving a modifier while excluding RecursiveDir, and add a GetItemSpecModifier overload that accepts ItemSpecModifierKind directly. - Update all callers (ProjectItemInstance.TaskItem, ProjectItem, Utilities.TaskItem, TaskParameter, BuiltInMetadata) to resolve once at the entry point and pass the kind through, removing 2-3 redundant TryGetModifierKind calls per metadata access.
Avoids boxing allocations when the array was implicitly cast to ICollection<string> or IEnumerable<string>, and ensures foreach loops use the struct enumerator with zero allocation. Updated all callers to iterate directly instead of calling AddRange.
- Reorder GetItemSpecModifier parameters to put itemSpec first (the subject), modifier/modifierKind second (the operation), and context parameters (currentDirectory, definingProjectEscaped) last.
MSBuild should clear the new "defining project cache" held by ItemSpecModifiers when a build ends to avoid unbounded growth in long-lived MSBuild processes.
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SimaTian
approved these changes
Mar 24, 2026
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Neat! |
This was referenced Mar 24, 2026
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Hi @DustinCampbell |
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Absolutely! Taking a look at the traces. |
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After diffing the "GC Heap Alloc Ignore Free (Coarse Sampling Stacks)" between the base line and worst runs, it looks like the problem is TaskItem, and it seems to be exasperated cross AppDomain . I expect that's because of the new Here's the increase in "TaskItem": 
And here arethe callers of "TaskItem": 
|
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Working on a fix via #13493. |
dfederm
pushed a commit
to dfederm/msbuild
that referenced
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Apr 9, 2026
…tInMetadata performance (dotnet#13386) I recommend reviewing this pull request commit-by-commit. # Summary of Changes - Introduce new MSBuild.Benchmarks project for tackling performance investigations. - Add a few benchmarks for various methods on `ItemSpecModifiers`. - Make several performance fixes related to `ItemSpecModifiers` and `BuildInMetadata`. - General clean up. Across the board, most benchmarks are **3×–35× faster** with **allocations eliminated or reduced by 93–100%**. The largest wins are in repeated-access and multi-item scenarios, which are the most representative of real build workloads. The full details are below but here are the highlights. ## Highlights ### 🚀 Speed Improvements (.NET 10.0) | Benchmark | Before | After | Speedup | |---|---|---|---| | `IsItemSpecModifier_AllModifiers` | 151.4 ns | 38.5 ns | **3.9×** | | `GetItemSpecModifier_DefiningProjectDirectory` | 812.2 ns | 72.4 ns | **11.2×** | | `TaskItem_AllDerivableModifiers_Once` | 434.5 ns | 87.4 ns | **5.0×** | | `TaskItem_FilenameAndExtension_Repeated` | 908.5 ns | 173.7 ns | **5.2×** | | `TaskItem_Filename_ManyItems` | 9,651 ns | 1,857 ns | **5.2×** | | `TaskItem_FullPathDerivedModifiers_Repeated` | 2,128 ns | 321.6 ns | **6.6×** | | `TaskItem_DefiningProjectDirectory_Repeated` | 9,121 ns | 970.8 ns | **9.4×** | | `PI_DefiningProjectDirectory_Repeated` | 9,092 ns | 1,021 ns | **8.9×** | | `PI_DefiningProjectFullPath_AllItems_Multi` | 35,245 ns | 9,947 ns | **3.5×** | | `PI_DefiningProjectDir_AllItems_Multi_Repeated` | 878,931 ns | 103,961 ns | **8.5×** | | `PI_FilenameExtension_AllItems` | 22,698 ns | 5,343 ns | **4.2×** | | `PI_FilenameExtension_AllItems_Repeated` | 181,612 ns | 67,028 ns | **2.7×** | ### 🧹 Allocation Reductions (.NET 10.0) | Benchmark | Before | After | Reduction | |---|---|---|---| | `TaskItem_AllDerivableModifiers_Once` | 1,232 B | **0 B** | 100% | | `TaskItem_FilenameAndExtension_Repeated` | 640 B | **0 B** | 100% | | `TaskItem_Filename_ManyItems` | 7,920 B | **0 B** | 100% | | `TaskItem_FullPathDerivedModifiers_Repeated` | 7,120 B | **0 B** | 100% | | `TaskItem_DefiningProjectDirectory_Repeated` | 8,240 B | **0 B** | 100% | | `TaskItem_AllDefiningProjectModifiers_Once` | 912 B | **0 B** | 100% | | `TaskItem_DefiningProjectNameExtension_AllItems` | 8,800 B | **0 B** | 100% | | `GetItemSpecModifier_DefiningProjectDirectory` | 536 B | **0 B** | 100% | | `PI_FilenameExtension_AllItems_Repeated` | 143,840 B | **640 B** | 99.6% | | `PI_DefiningProjectDir_AllItems_Multi_Repeated` | 824,640 B | **640 B** | 99.9% | | `PI_FilenameExtension_AllItems` | 14,384 B | **64 B** | 99.6% | | `PI_DefiningProjectDirectory_Repeated` | 8,304 B | **64 B** | 99.2% | | `PI_AllDerivableModifiers_Once` | 1,296 B | **64 B** | 95.1% | | `PI_AllDefiningProjectModifiers_Once` | 976 B | **64 B** | 93.4% | ### 📊 .NET Framework 4.8.1 | Benchmark | Before | After | Speedup | |---|---|---|---| | `GetItemSpecModifier_DefiningProjectDirectory` | 5,467 ns | 156.8 ns | **34.9×** | | `TaskItem_DefiningProjectDirectory_Repeated` | 58,025 ns | 2,539 ns | **22.9×** | | `PI_DefiningProjectDir_AllItems_Multi_Repeated` | 6,399 μs | 282.3 μs | **22.7×** | | `TaskItem_Filename_ManyItems` | 110,078 ns | 6,916 ns | **15.9×** | | `TaskItem_FullPathDerivedModifiers_Repeated` | 26,619 ns | 2,262 ns | **11.8×** | | `PI_FilenameExtension_AllItems_Repeated` | 2,162 μs | 202.6 μs | **10.7×** | | `TaskItem_AllDerivableModifiers_Once` | 5,322 ns | 507.2 ns | **10.5×** | | `PI_FilenameExtension_AllItems` | 216,406 ns | 20,366 ns | **10.6×** | | `TaskItem_FilenameAndExtension_Repeated` | 10,238 ns | 664.7 ns | **15.4×** | | `PI_AllDerivableModifiers_Once` | 5,525 ns | 688.6 ns | **8.0×** | | `PI_DefiningProjectDirectory_Repeated` | 64,204 ns | 2,796 ns | **23.0×** | | `PI_AllDefiningProjectModifiers_Once` | 9,808 ns | 1,154 ns | **8.5×** | | `TaskItem_AllDefiningProjectModifiers_Once` | 8,636 ns | 965.3 ns | **8.9×** | ## 'Quick-and-Dirty' Telemetry I had Copilot write some "quick-and-dirty" telemetry to track information in `ItemSpecModifiers` and dump it to a file. I built MSBuild with that extra telemetry and then built Roslyn (starting from `Microsoft.VisualStudio.LanguageServices.CSharp.csproj`) using that MSBuild. This gave me a dump with loads of interesting details. For example, `IsItemSpecModifier` was called 901,057 times. <details> <summary><b>Full Quick-and-Dirty Telemetry Dump</b></summary> ``` === ItemSpecModifiers Telemetry (2026-03-12T09:38:41.0365991-07:00) === --- Top-level method calls --- IsItemSpecModifier: 901,057 IsDerivableItemSpecModifier: 144,857 GetItemSpecModifier: 180,890 --- Compute helper calls --- ComputeFullPath: 75,443 ComputeRootDir: 84 ComputeFilename: 57,426 ComputeExtension: 32,071 ComputeRelativeDir: 22 ComputeDirectory: 84 ComputeModifiedTime: 0 ComputeCreatedTime: 0 ComputeAccessedTime: 0 --- Per-modifier breakdown (inside GetItemSpecModifier) --- FullPath: 44,783 RootDir: 41 Filename: 57,426 Extension: 6,462 RelativeDir: 22 Directory: 41 RecursiveDir: 0 Identity: 15,814 ModifiedTime: 0 CreatedTime: 0 AccessedTime: 0 DefiningProjectFullPath: 30,535 DefiningProjectDirectory: 43 DefiningProjectName: 0 DefiningProjectExtension: 25,609 ========================================================== Per-ItemSpec Modifier Hit Matrix ========================================================== Unique item specs seen: 13,809 Item specs hit > 1 time: 13,005 Grand total modifier lookups: 180,890 --- Top 50 hottest item specs (by total modifier calls) --- #1 (1,502 calls): System.Runtime.CompilerServices.InternalsVisibleTo Identity 751 DefiningProjectFullPath 751 #2 (380 calls): D:\Projects\roslyn\artifacts\bin\Microsoft.CodeAnalysis\Debug\netstandard2.0\Microsoft.CodeAnalysis.dll FullPath 17 Filename 280 Extension 40 Identity 21 DefiningProjectFullPath 22 #3 (270 calls): D:\Projects\roslyn\artifacts\bin\Microsoft.CodeAnalysis.Scripting\Debug\netstandard2.0\Microsoft.CodeAnalysis.Scripting.dll FullPath 12 Filename 195 Extension 30 Identity 16 DefiningProjectFullPath 17 #4 (270 calls): D:\Projects\roslyn\artifacts\bin\Microsoft.CodeAnalysis.Workspaces\Debug\netstandard2.0\Microsoft.CodeAnalysis.Workspaces.dll FullPath 12 Filename 195 Extension 30 Identity 16 DefiningProjectFullPath 17 #5 (247 calls): D:\.nuget\packages\system.threading.tasks.extensions\4.6.3\lib\netstandard2.0\System.Threading.Tasks.Extensions.dll FullPath 13 Filename 221 Identity 13 #6 (247 calls): D:\.nuget\packages\system.memory\4.6.3\lib\netstandard2.0\System.Memory.dll FullPath 13 Filename 221 Identity 13 #7 (247 calls): D:\.nuget\packages\system.buffers\4.6.1\lib\netstandard2.0\System.Buffers.dll FullPath 13 Filename 221 Identity 13 #8 (247 calls): D:\.nuget\packages\system.numerics.vectors\4.6.1\lib\netstandard2.0\System.Numerics.Vectors.dll FullPath 13 Filename 221 Identity 13 #9 (247 calls): D:\.nuget\packages\system.text.encoding.codepages\8.0.0\lib\netstandard2.0\System.Text.Encoding.CodePages.dll FullPath 13 Filename 221 Identity 13 #10 (247 calls): D:\.nuget\packages\system.runtime.compilerservices.unsafe\6.1.2\lib\netstandard2.0\System.Runtime.CompilerServices.Unsafe.dll FullPath 13 Filename 221 Identity 13 #11 (245 calls): D:\.nuget\packages\microsoft.dotnet.arcade.sdk\10.0.0-beta.26160.1\tools\Assets\DotNetPackageIcon.png FullPath 48 Filename 40 Extension 70 Identity 2 DefiningProjectFullPath 37 DefiningProjectDirectory 8 DefiningProjectExtension 40 #12 (245 calls): D:\Projects\roslyn\eng\targets\..\..\src\NuGet\ThirdPartyNotices.rtf FullPath 48 Filename 40 Extension 70 Identity 2 DefiningProjectFullPath 37 DefiningProjectDirectory 8 DefiningProjectExtension 40 #13 (240 calls): D:\.nuget\packages\system.collections.immutable\10.0.1\lib\netstandard2.0\System.Collections.Immutable.dll FullPath 12 Filename 216 Identity 12 #14 (240 calls): D:\.nuget\packages\system.reflection.metadata\10.0.1\lib\netstandard2.0\System.Reflection.Metadata.dll FullPath 12 Filename 216 Identity 12 #15 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Web.dll FullPath 13 Filename 208 Identity 13 dotnet#16 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Threading.ThreadPool.dll FullPath 13 Filename 208 Identity 13 dotnet#17 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.IO.FileSystem.Watcher.dll FullPath 13 Filename 208 Identity 13 dotnet#18 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Resources.ResourceManager.dll FullPath 13 Filename 208 Identity 13 dotnet#19 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.IO.dll FullPath 13 Filename 208 Identity 13 dotnet#20 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.IO.Pipes.dll FullPath 13 Filename 208 Identity 13 dotnet#21 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.IO.MemoryMappedFiles.dll FullPath 13 Filename 208 Identity 13 dotnet#22 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.ValueTuple.dll FullPath 13 Filename 208 Identity 13 dotnet#23 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Console.dll FullPath 13 Filename 208 Identity 13 dotnet#24 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Linq.Parallel.dll FullPath 13 Filename 208 Identity 13 dotnet#25 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Security.Claims.dll FullPath 13 Filename 208 Identity 13 dotnet#26 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.IO.UnmanagedMemoryStream.dll FullPath 13 Filename 208 Identity 13 dotnet#27 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Threading.Overlapped.dll FullPath 13 Filename 208 Identity 13 dotnet#28 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Drawing.Primitives.dll FullPath 13 Filename 208 Identity 13 dotnet#29 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Net.WebSockets.dll FullPath 13 Filename 208 Identity 13 dotnet#30 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Security.Cryptography.Algorithms.dll FullPath 13 Filename 208 Identity 13 dotnet#31 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.IO.FileSystem.DriveInfo.dll FullPath 13 Filename 208 Identity 13 dotnet#32 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Diagnostics.Tracing.dll FullPath 13 Filename 208 Identity 13 dotnet#33 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Linq.Expressions.dll FullPath 13 Filename 208 Identity 13 dotnet#34 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Security.Principal.dll FullPath 13 Filename 208 Identity 13 dotnet#35 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Globalization.Calendars.dll FullPath 13 Filename 208 Identity 13 dotnet#36 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Security.Cryptography.Primitives.dll FullPath 13 Filename 208 Identity 13 dotnet#37 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.ObjectModel.dll FullPath 13 Filename 208 Identity 13 dotnet#38 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Xml.XDocument.dll FullPath 13 Filename 208 Identity 13 dotnet#39 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Collections.dll FullPath 13 Filename 208 Identity 13 dotnet#40 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.ComponentModel.TypeConverter.dll FullPath 13 Filename 208 Identity 13 dotnet#41 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Runtime.InteropServices.dll FullPath 13 Filename 208 Identity 13 dotnet#42 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Collections.Concurrent.dll FullPath 13 Filename 208 Identity 13 dotnet#43 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Collections.Specialized.dll FullPath 13 Filename 208 Identity 13 dotnet#44 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Dynamic.Runtime.dll FullPath 13 Filename 208 Identity 13 dotnet#45 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Net.Requests.dll FullPath 13 Filename 208 Identity 13 dotnet#46 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Security.Cryptography.X509Certificates.dll FullPath 13 Filename 208 Identity 13 dotnet#47 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Net.dll FullPath 13 Filename 208 Identity 13 dotnet#48 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.IO.Compression.ZipFile.dll FullPath 13 Filename 208 Identity 13 dotnet#49 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Xml.XmlSerializer.dll FullPath 13 Filename 208 Identity 13 dotnet#50 (234 calls): D:\.nuget\packages\netstandard.library\2.0.3\build\netstandard2.0\ref\System.Runtime.CompilerServices.VisualC.dll FullPath 13 Filename 208 Identity 13 --- Repetition histogram (total modifier calls per item spec → count of item specs) --- 1,502 calls → 1 item specs 380 calls → 1 item specs 270 calls → 2 item specs 247 calls → 6 item specs 245 calls → 2 item specs 240 calls → 2 item specs 234 calls → 112 item specs 226 calls → 1 item specs 224 calls → 2 item specs 204 calls → 4 item specs 196 calls → 1 item specs 164 calls → 13 item specs 160 calls → 2 item specs 151 calls → 3 item specs 144 calls → 53 item specs 140 calls → 6 item specs 138 calls → 4 item specs 134 calls → 1 item specs 132 calls → 7 item specs 122 calls → 2 item specs 117 calls → 14 item specs 113 calls → 124 item specs 111 calls → 1 item specs 110 calls → 2 item specs 109 calls → 1 item specs 101 calls → 3 item specs 100 calls → 2 item specs 99 calls → 1 item specs 98 calls → 1 item specs 91 calls → 5 item specs 89 calls → 59 item specs 86 calls → 2 item specs 84 calls → 1 item specs 82 calls → 2 item specs 80 calls → 7 item specs 78 calls → 1 item specs 76 calls → 2 item specs 75 calls → 1 item specs 74 calls → 5 item specs 73 calls → 3 item specs 72 calls → 2 item specs 70 calls → 1 item specs 66 calls → 5 item specs 65 calls → 5 item specs 60 calls → 10 item specs 58 calls → 8 item specs 57 calls → 1 item specs 56 calls → 1 item specs 54 calls → 6 item specs 52 calls → 3 item specs 51 calls → 8 item specs 50 calls → 1 item specs 49 calls → 2 item specs 48 calls → 3 item specs 47 calls → 1 item specs 46 calls → 1 item specs 45 calls → 13 item specs 44 calls → 20 item specs 41 calls → 2 item specs 40 calls → 8 item specs 39 calls → 1 item specs 37 calls → 4 item specs 36 calls → 51 item specs 35 calls → 5 item specs 34 calls → 1 item specs 33 calls → 1 item specs 32 calls → 2 item specs 30 calls → 4 item specs 29 calls → 11 item specs 28 calls → 20 item specs 27 calls → 11 item specs 26 calls → 16 item specs 24 calls → 30 item specs 23 calls → 3 item specs 22 calls → 153 item specs 21 calls → 1 item specs 20 calls → 26 item specs 19 calls → 1 item specs 18 calls → 109 item specs 16 calls → 30 item specs 15 calls → 35 item specs 14 calls → 383 item specs 13 calls → 166 item specs 12 calls → 1,051 item specs 11 calls → 1 item specs 10 calls → 70 item specs 9 calls → 43 item specs 8 calls → 7,012 item specs 7 calls → 50 item specs 6 calls → 910 item specs 5 calls → 1,420 item specs 4 calls → 449 item specs 3 calls → 32 item specs 2 calls → 340 item specs 1 calls → 804 item specs ``` </details> ## Initial Benchmark Results ### .NET 10.0 | Method | Mean | Error | StdDev | Gen0 | Allocated | |--------------------------------------------- |--------------:|------------:|------------:|-------:|----------:| | IsItemSpecModifier_AllModifiers | 151.425 ns | 0.1309 ns | 0.1161 ns | - | - | | IsDerivableItemSpecModifier_RecursiveDir | 2.522 ns | 0.0028 ns | 0.0025 ns | - | - | | GetItemSpecModifier_FullPath | 267.552 ns | 0.3441 ns | 0.3050 ns | - | - | | GetItemSpecModifier_Directory | 359.023 ns | 0.7603 ns | 0.6740 ns | 0.0224 | 376 B | | GetItemSpecModifier_ModifiedTime | 28,544.061 ns | 237.0185 ns | 221.7073 ns | - | 176 B | | GetItemSpecModifier_DefiningProjectDirectory | 812.229 ns | 3.3636 ns | 2.9817 ns | 0.0315 | 536 B | | TaskItem_AllDerivableModifiers_Once | 434.5 ns | 4.36 ns | 4.08 ns | 0.0734 | 1232 B | | TaskItem_FilenameAndExtension_Repeated | 908.5 ns | 1.13 ns | 1.00 ns | 0.0381 | 640 B | | TaskItem_Filename_ManyItems | 9,651.3 ns | 29.02 ns | 25.72 ns | 0.4730 | 7920 B | | TaskItem_FullPathDerivedModifiers_Repeated | 2,127.6 ns | 7.45 ns | 6.60 ns | 0.4234 | 7120 B | | ProjectItemInstance_AllDerivableModifiers_Once | 513.4 ns | 2.93 ns | 2.74 ns | 0.0772 | 1296 B | | ProjectItemInstance_FilenameExtension_AllItems | 22,697.6 ns | 68.62 ns | 64.19 ns | 0.8545 | 14384 B | | ProjectItemInstance_FilenameExtension_AllItems_Repeated | 181,612.2 ns | 1,125.69 ns | 940.00 ns | 8.5449 | 143840 B | | ProjectItemInstance_AllDefiningProjectModifiers_Once | 1.559 μs | 0.0047 μs | 0.0040 μs | 0.0572 | 976 B | | ProjectItemInstance_DefiningProjectDirectory_Repeated | 9.092 μs | 0.0654 μs | 0.0580 μs | 0.4883 | 8304 B | | ProjectItemInstance_DefiningProjectNameExtension_AllItems_SingleProject | 12.515 μs | 0.0297 μs | 0.0263 μs | 0.5188 | 8864 B | | ProjectItemInstance_DefiningProjectFullPath_AllItems_MultiProject | 35.245 μs | 0.0405 μs | 0.0379 μs | - | 64 B | | ProjectItemInstance_DefiningProjectDirectory_AllItems_MultiProject_Repeated | 878.931 μs | 3.1495 μs | 2.7919 μs | 48.8281 | 824640 B | | TaskItem_AllDefiningProjectModifiers_Once | 1.430 μs | 0.0027 μs | 0.0023 μs | 0.0534 | 912 B | | TaskItem_DefiningProjectNameExtension_AllItems | 11.628 μs | 0.0289 μs | 0.0241 μs | 0.5188 | 8800 B | | TaskItem_DefiningProjectDirectory_Repeated | 9.121 μs | 0.0192 μs | 0.0170 μs | 0.4883 | 8240 B | ### .NET Framework 4.8.1 | Method | Mean | Error | StdDev | Gen0 | Allocated | |--------------------------------------------- |-------------:|-----------:|----------:|-------:|----------:| | IsItemSpecModifier_AllModifiers | 227.45 ns | 0.297 ns | 0.264 ns | - | - | | IsDerivableItemSpecModifier_RecursiveDir | 10.49 ns | 0.019 ns | 0.018 ns | - | - | | GetItemSpecModifier_FullPath | 1,267.45 ns | 0.844 ns | 0.705 ns | - | - | | GetItemSpecModifier_Directory | 2,433.43 ns | 7.400 ns | 6.560 ns | 0.0954 | 517 B | | GetItemSpecModifier_ModifiedTime | 41,881.06 ns | 111.954 ns | 93.487 ns | 0.1221 | 878 B | | GetItemSpecModifier_DefiningProjectDirectory | 5,467.24 ns | 8.295 ns | 6.926 ns | 0.1602 | 857 B | | TaskItem_AllDerivableModifiers_Once | 5.322 μs | 0.0354 μs | 0.0331 μs | 0.3662 | 1923 B | | TaskItem_FilenameAndExtension_Repeated | 10.238 μs | 0.0108 μs | 0.0101 μs | 0.1373 | 761 B | | TaskItem_Filename_ManyItems | 110.078 μs | 0.1367 μs | 0.1212 μs | 2.3193 | 12379 B | | TaskItem_FullPathDerivedModifiers_Repeated | 26.619 μs | 0.1695 μs | 0.1585 μs | 2.1973 | 11578 B | | ProjectItemInstance_AllDerivableModifiers_Once | 5.525 μs | 0.0311 μs | 0.0276 μs | 0.3662 | 1959 B | | ProjectItemInstance_FilenameExtension_AllItems | 216.406 μs | 0.2767 μs | 0.2160 μs | 2.9297 | 16422 B | | ProjectItemInstance_FilenameExtension_AllItems_Repeated | 2,161.623 μs | 10.4073 μs | 9.2258 μs | 31.2500 | 164225 B | | ProjectItemInstance_AllDefiningProjectModifiers_Once | 9.808 μs | 0.0177 μs | 0.0165 μs | 0.2594 | 1418 B | | ProjectItemInstance_DefiningProjectDirectory_Repeated | 64.204 μs | 0.3983 μs | 0.3726 μs | 2.3193 | 12616 B | | ProjectItemInstance_DefiningProjectNameExtension_AllItems_SingleProject | 131.504 μs | 0.3383 μs | 0.3165 μs | 2.1973 | 12456 B | | ProjectItemInstance_DefiningProjectFullPath_AllItems_MultiProject | 173.171 μs | 0.7242 μs | 0.5654 μs | - | 38 B | | ProjectItemInstance_DefiningProjectDirectory_AllItems_MultiProject_Repeated | 6,399.063 μs | 71.6927 μs | 67.0614 μs | 234.3750 | 1242225 B | | TaskItem_AllDefiningProjectModifiers_Once | 8.636 μs | 0.0177 μs | 0.0147 μs | 0.2594 | 1382 B | | TaskItem_DefiningProjectNameExtension_AllItems | 126.982 μs | 0.2250 μs | 0.2104 μs | 2.1973 | 12420 B | | TaskItem_DefiningProjectDirectory_Repeated | 58.025 μs | 0.1388 μs | 0.1299 μs | 2.3804 | 12579 B | ## Final Benchmark Results ### .NET 10.0 | Method | Mean | Error | StdDev | Gen0 | Allocated | |--------------------------------------------- |--------------:|------------:|------------:|-------:|----------:| | IsItemSpecModifier_AllModifiers | 38.4923 ns | 0.5501 ns | 0.5145 ns | - | - | | IsDerivableItemSpecModifier_RecursiveDir | 0.0000 ns | 0.0000 ns | 0.0000 ns | - | - | | GetItemSpecModifier_FullPath | 260.1019 ns | 0.3623 ns | 0.3212 ns | - | - | | GetItemSpecModifier_Directory | 413.2121 ns | 1.9441 ns | 1.8185 ns | 0.0224 | 376 B | | GetItemSpecModifier_ModifiedTime | 30,272.3116 ns | 408.0450 ns | 381.6855 ns | - | 176 B | | GetItemSpecModifier_DefiningProjectDirectory | 72.3691 ns | 0.0289 ns | 0.0270 ns | - | - | | TaskItem_AllDerivableModifiers_Once | 87.41 ns | 0.226 ns | 0.200 ns | - | - | | TaskItem_FilenameAndExtension_Repeated | 173.68 ns | 1.812 ns | 1.695 ns | - | - | | TaskItem_Filename_ManyItems | 1,856.79 ns | 1.128 ns | 0.942 ns | - | - | | TaskItem_FullPathDerivedModifiers_Repeated | 321.57 ns | 0.301 ns | 0.267 ns | - | - | | ProjectItemInstance_AllDerivableModifiers_Once | 143.78 ns | 0.493 ns | 0.462 ns | 0.0038 | 64 B | | ProjectItemInstance_FilenameExtension_AllItems | 5,343.30 ns | 4.955 ns | 4.138 ns | - | 64 B | | ProjectItemInstance_FilenameExtension_AllItems_Repeated | 67,028.30 ns | 252.985 ns | 224.264 ns | - | 640 B | | ProjectItemInstance_AllDefiningProjectModifiers_Once | 459.4 ns | 0.34 ns | 0.31 ns | 0.0038 | 64 B | | ProjectItemInstance_DefiningProjectDirectory_Repeated | 1,020.5 ns | 0.56 ns | 0.47 ns | 0.0038 | 64 B | | ProjectItemInstance_DefiningProjectNameExtension_AllItems_SingleProject | 20,091.0 ns | 17.96 ns | 16.80 ns | - | 64 B | | ProjectItemInstance_DefiningProjectFullPath_AllItems_MultiProject | 9,946.7 ns | 5.28 ns | 4.68 ns | - | 64 B | | ProjectItemInstance_DefiningProjectDirectory_AllItems_MultiProject_Repeated | 103,960.5 ns | 57.74 ns | 48.21 ns | - | 640 B | | TaskItem_AllDefiningProjectModifiers_Once | 400.5 ns | 0.15 ns | 0.12 ns | - | - | | TaskItem_DefiningProjectNameExtension_AllItems | 19,150.3 ns | 11.55 ns | 10.24 ns | - | - | | TaskItem_DefiningProjectDirectory_Repeated | 970.8 ns | 0.62 ns | 0.55 ns | - | - | ### .NET Framework 4.8.1 | Method | Mean | Error | StdDev | Gen0 | Allocated | |--------------------------------------------- |-------------:|-----------:|----------:|-------:|----------:| | IsItemSpecModifier_AllModifiers | 106.532 ns | 0.4289 ns | 0.4012 ns | - | - | | IsDerivableItemSpecModifier_RecursiveDir | 5.067 ns | 0.0031 ns | 0.0024 ns | - | - | | GetItemSpecModifier_FullPath | 1,331.138 ns | 1.4666 ns | 1.3001 ns | - | - | | GetItemSpecModifier_Directory | 2,471.887 ns | 4.2333 ns | 3.7527 ns | 0.0954 | 517 B | | GetItemSpecModifier_ModifiedTime | 44,773.794 ns | 405.2647 ns | 359.2566 ns | 0.1221 | 878 B | | GetItemSpecModifier_DefiningProjectDirectory | 156.840 ns | 0.2242 ns | 0.1987 ns | - | - | | TaskItem_AllDerivableModifiers_Once | 507.2 ns | 1.19 ns | 1.11 ns | - | - | | TaskItem_FilenameAndExtension_Repeated | 664.7 ns | 0.39 ns | 0.35 ns | - | - | | TaskItem_Filename_ManyItems | 6,916.2 ns | 4.03 ns | 3.77 ns | - | - | | TaskItem_FullPathDerivedModifiers_Repeated | 2,261.6 ns | 3.34 ns | 2.96 ns | - | - | | ProjectItemInstance_AllDerivableModifiers_Once | 688.6 ns | 1.01 ns | 0.94 ns | 0.0067 | 36 B | | ProjectItemInstance_FilenameExtension_AllItems | 20,366.3 ns | 11.28 ns | 10.56 ns | - | 36 B | | ProjectItemInstance_FilenameExtension_AllItems_Repeated | 202,570.4 ns | 271.12 ns | 240.34 ns | - | 362 B | | ProjectItemInstance_AllDefiningProjectModifiers_Once | 1,153.5 ns | 13.83 ns | 12.26 ns | 0.0057 | 36 B | | ProjectItemInstance_DefiningProjectDirectory_Repeated | 2,795.7 ns | 17.33 ns | 16.21 ns | 0.0038 | 36 B | | ProjectItemInstance_DefiningProjectNameExtension_AllItems_SingleProject | 46,236.9 ns | 105.16 ns | 93.22 ns | - | 36 B | | ProjectItemInstance_DefiningProjectFullPath_AllItems_MultiProject | 28,362.1 ns | 34.50 ns | 30.58 ns | - | 36 B | | ProjectItemInstance_DefiningProjectDirectory_AllItems_MultiProject_Repeated | 282,316.9 ns | 1,944.00 ns | 1,818.42 ns | - | 364 B | | TaskItem_AllDefiningProjectModifiers_Once | 965.3 ns | 5.43 ns | 4.53 ns | - | - | | TaskItem_DefiningProjectNameExtension_AllItems | 42,707.8 ns | 179.84 ns | 168.23 ns | - | - | | TaskItem_DefiningProjectDirectory_Repeated | 2,539.1 ns | 9.64 ns | 8.05 ns | - | - |
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Summary of Changes
ItemSpecModifiers.ItemSpecModifiersandBuildInMetadata.Across the board, most benchmarks are 3×–35× faster with allocations eliminated or reduced by 93–100%. The largest wins are in repeated-access and multi-item scenarios, which are the most representative of real build workloads. The full details are below but here are the highlights.
Highlights
🚀 Speed Improvements (.NET 10.0)
IsItemSpecModifier_AllModifiersGetItemSpecModifier_DefiningProjectDirectoryTaskItem_AllDerivableModifiers_OnceTaskItem_FilenameAndExtension_RepeatedTaskItem_Filename_ManyItemsTaskItem_FullPathDerivedModifiers_RepeatedTaskItem_DefiningProjectDirectory_RepeatedPI_DefiningProjectDirectory_RepeatedPI_DefiningProjectFullPath_AllItems_MultiPI_DefiningProjectDir_AllItems_Multi_RepeatedPI_FilenameExtension_AllItemsPI_FilenameExtension_AllItems_Repeated🧹 Allocation Reductions (.NET 10.0)
TaskItem_AllDerivableModifiers_OnceTaskItem_FilenameAndExtension_RepeatedTaskItem_Filename_ManyItemsTaskItem_FullPathDerivedModifiers_RepeatedTaskItem_DefiningProjectDirectory_RepeatedTaskItem_AllDefiningProjectModifiers_OnceTaskItem_DefiningProjectNameExtension_AllItemsGetItemSpecModifier_DefiningProjectDirectoryPI_FilenameExtension_AllItems_RepeatedPI_DefiningProjectDir_AllItems_Multi_RepeatedPI_FilenameExtension_AllItemsPI_DefiningProjectDirectory_RepeatedPI_AllDerivableModifiers_OncePI_AllDefiningProjectModifiers_Once📊 .NET Framework 4.8.1
GetItemSpecModifier_DefiningProjectDirectoryTaskItem_DefiningProjectDirectory_RepeatedPI_DefiningProjectDir_AllItems_Multi_RepeatedTaskItem_Filename_ManyItemsTaskItem_FullPathDerivedModifiers_RepeatedPI_FilenameExtension_AllItems_RepeatedTaskItem_AllDerivableModifiers_OncePI_FilenameExtension_AllItemsTaskItem_FilenameAndExtension_RepeatedPI_AllDerivableModifiers_OncePI_DefiningProjectDirectory_RepeatedPI_AllDefiningProjectModifiers_OnceTaskItem_AllDefiningProjectModifiers_Once'Quick-and-Dirty' Telemetry
I had Copilot write some "quick-and-dirty" telemetry to track information in
ItemSpecModifiersand dump it to a file. I built MSBuild with that extra telemetry and then built Roslyn (starting fromMicrosoft.VisualStudio.LanguageServices.CSharp.csproj) using that MSBuild. This gave me a dump with loads of interesting details. For example,IsItemSpecModifierwas called 901,057 times.Full Quick-and-Dirty Telemetry Dump
Initial Benchmark Results
.NET 10.0
.NET Framework 4.8.1
Final Benchmark Results
.NET 10.0
.NET Framework 4.8.1