VS2017 RC - Colorization causing slow editing in large files #1821
Description
If you open a large file (e.g. TypeChecker.fs or CompileOps.fs) then character-by-character editing is noticably slow, much slower than in VS2012-15.
The underlying problem is large CPU time usage by the routine AddSyntacticClassificationsAsync. Here are the top entries for a profiling run for 20 seconds of editing (this was using a debug build of Visual F# Tools, but the same results should apply to a release build )
Function Name Total CPU (ms) Total CPU (%) Self CPU (ms) Self CPU (%) Module
- <StartupCode$FSharp-Editor>.$ColorizationService+Microsoft-CodeAnalysis-Editor-IEditorClassificationService-AddSyntacticClassificationsAsync@138::Invoke 14055 48.06% 0 0.00% FSharp.Editor.dll
| - Microsoft.VisualStudio.FSharp.Editor.FSharpColorizationService::GetColorizationData 14011 47.91% 139 0.48% FSharp.Editor.dll
|| - Microsoft.VisualStudio.FSharp.Editor.FSharpColorizationService::scanSourceLine 12726 43.52% 140 0.48% FSharp.Editor.dll
||| - <StartupCode$FSharp-Editor>.$ColorizationService+scanAndColorNextToken@62::Invoke 11465 39.20% 219 0.75% FSharp.Editor.dll
|||| - Microsoft.FSharp.Compiler.SourceCodeServices.FSharpLineTokenizer::ScanToken 10861 37.14% 527 1.80% FSharp.LanguageService.Compiler.dll
||||| + <StartupCode$FSharp-LanguageService-Compiler>.$ServiceLexing+GetTokenWithPosition@569::Invoke 4487 15.34% 349 1.19% FSharp.LanguageService.Compiler.dll
||||| + <StartupCode$FSharp-LanguageService-Compiler>.$ServiceLexing+FinalState@675::Invoke 2141 7.32% 11 0.04% FSharp.LanguageService.Compiler.dll
||||| + Microsoft.FSharp.Compiler.SourceCodeServices.LexerStateEncoding::decodeLexInt 1025 3.50% 170 0.58% FSharp.LanguageService.Compiler.dll
Repro steps
-
Open VisualFSharp.sln and go to COmpileOps.fs ot TYpeChecker,fs
-
Randomly delete characters and revert changes
-
Repeat this
- at the start of large files in projects
- at the end of large files in projects
- at the start of large scripts
- at the end of large scripts
- at the start of large files out of projects
- at the end of large files out of projects
Expected behavior
Fast editing
Actual behavior
Slow editing
Known workarounds
Use small code files :)