better formatting of stats

Author: majocha

src/Compiler/Driver/fsc.fs

@@ -569,6 +569,7 @@ let main1
             exiter.Exit 1
 
     if tcConfig.showTimes then
+        Caches.CacheMetrics.CaptureStatsAndWriteToConsole() |> disposables.Register
         Activity.Profiling.addConsoleListener () |> disposables.Register
 
     tcConfig.writeTimesToFile

src/Compiler/Utilities/Caches.fs

@@ -7,6 +7,7 @@ open System.Collections.Concurrent
 open System.Threading
 open System.Diagnostics
 open System.Diagnostics.Metrics
+open System.IO
 
 module CacheMetrics =
     let Meter = new Meter("FSharp.Compiler.Cache")
@@ -92,16 +93,55 @@ module CacheMetrics =
             | _ -> assert false)
 
         listener.Start()
+        listener :> IDisposable
 
     let StatsToString () =
-        let sb = Text.StringBuilder()
-        sb.AppendLine "Cache Metrics:" |> ignore
+        use sw = new StringWriter()
+
+        let nameColumnWidth =
+            [ yield! statsByName.Keys; "Cache name" ] |> Seq.map String.length |> Seq.max
+
+        let ratioColumnWidth = "hit-ratio".Length
+        let columns = allCounters |> List.map _.Name
+        let columnWidths = columns |> List.map String.length |> List.map (max 8)
+
+        let totalWidth =
+            1 + nameColumnWidth :: ratioColumnWidth :: columnWidths
+            |> List.map ((+) 3)
+            |> List.sum
+
+        sw.WriteLine(String('-', totalWidth))
+        let cacheNameHeader = "Cache name".PadRight nameColumnWidth
+        sw.Write $"| {cacheNameHeader} | hit-ratio |"
+
+        for w, c in (columnWidths, columns) ||> List.zip do
+            sw.Write $" {c.PadLeft w} |"
+
+        sw.WriteLine()
+        sw.WriteLine(String('-', totalWidth))
 
         for kv in statsByName do
-            sb.AppendLine $"Cache {kv.Key}: {kv.Value}" |> ignore
+            let name = kv.Key
+            let stats = kv.Value
+            let totals = stats.GetTotals()
+            sw.Write $"| {name.PadLeft nameColumnWidth} | {stats.Ratio, 9:P2} |"
 
-        sb.AppendLine() |> ignore
-        string sb
+            for w, c in (columnWidths, columns) ||> List.zip do
+                sw.Write $" {totals[c].ToString().PadLeft(w)} |"
+
+            sw.WriteLine()
+
+        sw.WriteLine(String('-', totalWidth))
+        string sw
+
+    let CaptureStatsAndWriteToConsole () =
+        let listener = ListenToAll()
+
+        { new IDisposable with
+            member _.Dispose() =
+                listener.Dispose()
+                Console.WriteLine(StatsToString())
+        }
 
     // Currently the Cache emits telemetry for raw cache events: hits, misses, evictions etc.
     // This type observes those counters and keeps a snapshot of readings. It is used in tests and can be used to print cache stats in debug mode.

src/Compiler/Utilities/Caches.fsi

@@ -8,8 +8,9 @@ module internal CacheMetrics =
     /// Global telemetry Meter for all caches. Exposed for testing purposes.
     /// Set FSHARP_OTEL_EXPORT environment variable to enable OpenTelemetry export to external collectors in tests.
     val Meter: Meter
-    val ListenToAll: unit -> unit
+    val ListenToAll: unit -> IDisposable
     val StatsToString: unit -> string
+    val CaptureStatsAndWriteToConsole: unit -> IDisposable
 
     /// A local listener that can be created for a specific Cache instance to get its metrics. For testing purposes only.
     [<Class>]

vsintegration/src/FSharp.Editor/Common/DebugHelpers.fs

@@ -31,6 +31,7 @@ open Config
 open System.Diagnostics.Metrics
 open System.Text
 open Microsoft.VisualStudio.Threading
+open Microsoft.VisualStudio.FSharp.Editor.CancellableTasks
 
 module FSharpOutputPane =
 
@@ -119,14 +120,15 @@ module FSharpServiceTelemetry =
 
         ActivitySource.AddActivityListener(listener)
 
-    let periodicallyDisplayCacheStats () =
-        backgroundTask {
-            CacheMetrics.ListenToAll()
+    let periodicallyDisplayCacheStats (disposalToken: Threading.CancellationToken) =
+        cancellableTask {
+            use _ = CacheMetrics.ListenToAll()
 
             while true do
                 do! Task.Delay(TimeSpan.FromSeconds 10.0)
                 FSharpOutputPane.logMsg (CacheMetrics.StatsToString())
         }
+        |> CancellableTask.start disposalToken
 
 #if DEBUG
     open OpenTelemetry.Resources

vsintegration/src/FSharp.Editor/LanguageService/LanguageService.fs

@@ -407,7 +407,8 @@ type internal FSharpPackage() as this =
 
                     globalOptions.BlockForCompletionItems <- false
 
-                    DebugHelpers.FSharpServiceTelemetry.periodicallyDisplayCacheStats () |> ignore
+                    DebugHelpers.FSharpServiceTelemetry.periodicallyDisplayCacheStats this.DisposalToken
+                    |> ignore
 
                 }
                 |> CancellableTask.startAsTask cancellationToken)