2.5% of CPU time in build is spent evaluating unnecessary Exists() in conditions for a solution-wide design-time build

[davkean]

This is from this same solution: dotnet/project-system#2789.

By default, MSBuild does not cache Exists checks for the same paths/files, this results in a non-trivial amount of time looking at the disk:

Turning on file caching via set MsBuildCacheFileExistence=1 results reduces this from 2.9% to 0.4%:

Given it is extremely unlikely that in most builds that evaluation has side-effects - can we please turn on caching by default?

[davkean]

tag @cdmihai

[cdmihai]

Ideally, we should have an IO cache that is shared across evaluation. See #2392 (comment).

Setting this environment variable on a dev machine is risky. CI machines should be fine though.

[ladipro]

This was addressed with EvaluationContext, specifically by maintaining a per-context file system cache. CPS can even share its own FS caches with MSBuild so evaluation doesn't have to go to disk at all for many such Exists() calls.

[ladipro]

An example callstack of CPS evaluating a project and MSBuild calling back to CPS to check if a file exists:

        Child SP               IP Call Site
0000005276b3a298 00007fff8ae9cae0 Microsoft.VisualStudio.ProjectSystem.DirectoryCache.FileExists(System.String)
0000005276b3a2a0 00007fff8aea1114 Microsoft.Build.FileSystem.DirectoryCacheFileSystemWrapper.FileOrDirectoryExists(System.String)
0000005276b3a2f0 00007fff8aea0f89 Microsoft.Build.Shared.FileUtilities.FileOrDirectoryExistsNoThrow(System.String, Microsoft.Build.Shared.FileSystem.IFileSystem)
0000005276b3a380 00007fff8ae9d8e5 Microsoft.Build.Evaluation.FunctionCallExpressionNode.BoolEvaluate(IConditionEvaluationState, Microsoft.Build.BackEnd.Logging.LoggingContext)
0000005276b3a520 00007fff8ae98920 Microsoft.Build.Evaluation.OperatorExpressionNode.TryBoolEvaluate(IConditionEvaluationState, Boolean ByRef, Microsoft.Build.BackEnd.Logging.LoggingContext)
0000005276b3a570 00007fff8ae9baef Microsoft.Build.Evaluation.AndExpressionNode.BoolEvaluate(IConditionEvaluationState, Microsoft.Build.BackEnd.Logging.LoggingContext)
0000005276b3a670 00007fff8ae98920 Microsoft.Build.Evaluation.OperatorExpressionNode.TryBoolEvaluate(IConditionEvaluationState, Boolean ByRef, Microsoft.Build.BackEnd.Logging.LoggingContext)
0000005276b3a6c0 00007fff8ae987e8 Microsoft.Build.Evaluation.GenericExpressionNode.Evaluate(IConditionEvaluationState, Microsoft.Build.BackEnd.Logging.LoggingContext)
0000005276b3a740 00007fff8ae93717 Microsoft.Build.Evaluation.ConditionEvaluator.EvaluateConditionCollectingConditionedProperties[[System.__Canon, mscorlib],[System.__Canon, mscorlib]](System.String, Microsoft.Build.Evaluation.ParserOptions, Microsoft.Build.Evaluation.Expander`2, Microsoft.Build.Evaluation.ExpanderOptions, System.Collections.Generic.Dictionary`2>, System.String, Microsoft.Build.Construction.ElementLocation, Microsoft.Build.BackEnd.Logging.ILoggingService, Microsoft.Build.Framework.BuildEventContext, Microsoft.Build.Shared.FileSystem.IFileSystem, Microsoft.Build.Evaluation.ProjectRootElementCacheBase, Microsoft.Build.BackEnd.Logging.LoggingContext)
0000005276b3a920 00007fff8ae6b4d6 Microsoft.Build.Evaluation.Evaluator`4[[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib]].EvaluateConditionCollectingConditionedProperties(Microsoft.Build.Construction.ProjectElement, System.String, Microsoft.Build.Evaluation.ExpanderOptions, Microsoft.Build.Evaluation.ParserOptions, Microsoft.Build.Evaluation.ProjectRootElementCacheBase)
0000005276b3aaa0 00007fff8ae68bff Microsoft.Build.Evaluation.Evaluator`4[[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib]].ExpandAndLoadImports(System.String, Microsoft.Build.Construction.ProjectImportElement, Microsoft.Build.BackEnd.SdkResolution.SdkResult ByRef)
0000005276b3ad50 00007fff8ae6816f Microsoft.Build.Evaluation.Evaluator`4[[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib]].EvaluateImportElement(System.String, Microsoft.Build.Construction.ProjectImportElement)
0000005276b3ae60 00007fff8ae640ae Microsoft.Build.Evaluation.Evaluator`4[[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib]].PerformDepthFirstPass(Microsoft.Build.Construction.ProjectRootElement)
0000005276b3b200 00007fff8ae682c3 Microsoft.Build.Evaluation.Evaluator`4[[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib]].EvaluateImportElement(System.String, Microsoft.Build.Construction.ProjectImportElement)
0000005276b3b310 00007fff8ae640ae Microsoft.Build.Evaluation.Evaluator`4[[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib]].PerformDepthFirstPass(Microsoft.Build.Construction.ProjectRootElement)
0000005276b3b6b0 00007fff8ae682c3 Microsoft.Build.Evaluation.Evaluator`4[[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib]].EvaluateImportElement(System.String, Microsoft.Build.Construction.ProjectImportElement)
0000005276b3b7c0 00007fff8ae63c6d Microsoft.Build.Evaluation.Evaluator`4[[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib]].PerformDepthFirstPass(Microsoft.Build.Construction.ProjectRootElement)
0000005276b3bb60 00007fff8ae58ca0 Microsoft.Build.Evaluation.Evaluator`4[[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib]].Evaluate()
0000005276b3c680 00007fff8ae50b80 Microsoft.Build.Evaluation.Evaluator`4[[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib],[System.__Canon, mscorlib]].Evaluate(Microsoft.Build.Evaluation.IEvaluatorData`4, Microsoft.Build.Evaluation.Project, Microsoft.Build.Construction.ProjectRootElement, Microsoft.Build.Evaluation.ProjectLoadSettings, Int32, Microsoft.Build.Collections.PropertyDictionary`1, Microsoft.Build.BackEnd.Logging.ILoggingService, Microsoft.Build.Evaluation.IItemFactory`2, Microsoft.Build.Evaluation.IToolsetProvider, Microsoft.Build.Evaluation.ProjectRootElementCacheBase, Microsoft.Build.Framework.BuildEventContext, Microsoft.Build.BackEnd.SdkResolution.ISdkResolverService, Int32, Microsoft.Build.Evaluation.Context.EvaluationContext, Boolean)
0000005276b3c780 00007fff8ae504d0 Microsoft.Build.Evaluation.Project+ProjectImpl.Reevaluate(Microsoft.Build.BackEnd.Logging.ILoggingService, Microsoft.Build.Evaluation.ProjectLoadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext)
0000005276b3c9b0 00007fff8ae4e7ef Microsoft.Build.Evaluation.Project+ProjectImpl.ReevaluateIfNecessary(Microsoft.Build.BackEnd.Logging.ILoggingService, Microsoft.Build.Evaluation.ProjectLoadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext)
0000005276b3ca30 00007fff8ae4e6fe Microsoft.Build.Evaluation.Project+ProjectImpl.ReevaluateIfNecessary(Microsoft.Build.BackEnd.Logging.ILoggingService, Microsoft.Build.Evaluation.Context.EvaluationContext)
0000005276b3ca60 00007fff8ae4e571 Microsoft.Build.Evaluation.Project+ProjectImpl.ReevaluateIfNecessary(Microsoft.Build.Evaluation.Context.EvaluationContext)
0000005276b3caa0 00007fff8ae4dee3 Microsoft.Build.Evaluation.Project+ProjectImpl.Initialize(System.Collections.Generic.IDictionary`2, System.String, System.String, Microsoft.Build.Evaluation.ProjectLoadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext)
0000005276b3cc60 00007fff8ae4d396 Microsoft.Build.Evaluation.Project..ctor(Microsoft.Build.Construction.ProjectRootElement, System.Collections.Generic.IDictionary`2, System.String, System.String, Microsoft.Build.Evaluation.ProjectCollection, Microsoft.Build.Evaluation.ProjectLoadSettings, Microsoft.Build.Evaluation.Context.EvaluationContext, Microsoft.Build.FileSystem.IDirectoryCacheFactory)
0000005276b3ccc0 00007fff8ae4cd10 Microsoft.Build.Evaluation.Project.FromProjectRootElement(Microsoft.Build.Construction.ProjectRootElement, Microsoft.Build.Definition.ProjectOptions)
0000005276b3cda0 00007fff8ae4b5f5 Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectImpl+c__DisplayClass141_1+b__2>d.MoveNext()
0000005276b3ce50 00007fff8ae4a88a System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1[[System.__Canon, mscorlib]].Start[[Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectImpl+c__DisplayClass141_1+b__2>d, Microsoft.VisualStudio.ProjectSystem.Implementation]](b__2>d ByRef)
0000005276b3cf00 00007fff8ae4a7d9 Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectImpl+c__DisplayClass141_1.b__2()

I have filed AB#1757017 to track adding EvaluationContext support to the legacy project system. Nothing actionable for MSBuild any more, closing.