F# VS editor: reduce background CPU load by gating expensive analyzers to the active document only - #20117
F# VS editor: reduce background CPU load by gating expensive analyzers to the active document only#20117xperiandri wants to merge 1 commit into
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- Add ActiveDocumentDetection module (IVsMonitorSelection-based helper) - Gate UnusedDeclarationsAnalyzer to active document - Gate SimplifyNameDiagnosticAnalyzer to active document - Gate FSharpInlayHintsService to active document - Gate UnusedOpensDiagnosticAnalyzer to active document - Add ActiveDocumentDetection.fs to FSharp.Editor.fsproj Fixes dotnet#20114
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It seems this can be controlled by VS host: 
Maybe it's possible to expose this setting for F#. |
| type internal SimplifyNameDiagnosticAnalyzer [<ImportingConstructor>] () = | ||
| type internal SimplifyNameDiagnosticAnalyzer | ||
| [<ImportingConstructor>] | ||
| ([<Import("Microsoft.VisualStudio.Shell.SVsServiceProvider")>] serviceProvider: IServiceProvider) = |
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Import("...") sets only the contract name. The parameter still requires IServiceProvider, but Visual Studio exports SVsServiceProvider. MEF rejects all four parts. Import SVsServiceProvider by type.
| /// Returns the document moniker (full file path) of the currently focused | ||
| /// editor window, or ValueNone if it cannot be determined. | ||
| let tryGetActiveDocumentMoniker (serviceProvider: IServiceProvider) : string voption = | ||
| match serviceProvider.GetService(typeof<SVsShellMonitorSelection>) with |
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Roslyn runs these callbacks on worker threads. This code calls UI-bound shell services without switching threads, so exceptions escape the fail-open path. Track selection on the UI thread and publish a thread-safe snapshot.
| | filePath -> | ||
| match tryGetActiveDocumentMoniker serviceProvider with | ||
| | ValueNone -> true // couldn't determine the active document, don't suppress analysis | ||
| | ValueSome activeMoniker -> String.Equals(activeMoniker, filePath, StringComparison.OrdinalIgnoreCase) |
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Results now depend on focus, but no provider invalidates results when focus moves between visible panes. Invalidate both documents on selection changes, or remove result-level gating.
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Fixes #20114
Summary
CPU profiling of
devenv.exe(VS Insiders + F# extension) showedThreadPoolWorkQueue.Dispatchat 72 % total / 59 % self, driven by continuous F# background analysis running for all open tabs, not just the active one.This PR implements the highest-impact P0 fixes from
docs/ide/background-activity-minimization-plan.md:Changes
New:
ActiveDocumentDetectionmodulevsintegration/src/FSharp.Editor/Diagnostics/ActiveDocumentDetection.fsShared helper that uses
IVsMonitorSelection/IVsWindowFrameto determine whether a RoslynDocumentis the currently focused VS editor tab.tryGetActiveDocumentMoniker— returnsstring voption(the active file path, orValueNone)isActiveDocument— returnsbool; falls back totrue(= don't suppress) when detection fails, so analysis is never silently lostGated analyzers / services
UnusedOpensDiagnosticAnalyzerActiveDocumentDetectionmoduleUnusedDeclarationsAnalyzerSimplifyNameDiagnosticAnalyzerFSharpInlayHintsServiceBehavior
BackgroundAnalysisScope.VisibleFilesAndOpenFilesWithPreviouslyReportedDiagnostics).Not in scope (tracked in the plan)
BackgroundAnalysisScopedefault change (item App.config in up-to-date check causes rebuilds #11) — needs a separate option keyCompilation.Emitversion-stamp cache (item Error while installing Visual F# Tools (05.01.2015) #5)hasDependentVersionChangedasync fix (item Method not fournd: SystemCollections.Generic IEqualityComparer'1 #6)ClassificationServicestale-result path (item Existing F# projects won't open if only VS2015 is installed #4)updateProjectOptionsdebounce (item Intellisense does not appear off of generic type #8)FSharpProjectOptionsReactorpriority queue (item Explicit field declaration generating property in F# classes #7)