Tweaks.

src/OpenTelemetry/Metrics/AggregatorStore.cs

@@ -17,6 +17,7 @@ internal sealed class AggregatorStore
     internal readonly int CardinalityLimit;
     internal readonly bool EmitOverflowAttribute;
     internal readonly ConcurrentDictionary<Tags, LookupData>? TagsToMetricPointIndexDictionaryDelta;
+    internal readonly ExemplarFilter ExemplarFilter;
     internal long DroppedMeasurements = 0;
 
     private static readonly string MetricPointCapHitFixMessage = "Consider opting in for the experimental SDK feature to emit all the throttled metrics under the overflow attribute by setting env variable OTEL_DOTNET_EXPERIMENTAL_METRICS_EMIT_OVERFLOW_ATTRIBUTE = true. You could also modify instrumentation to reduce the number of unique key/value pair combinations. Or use Views to drop unwanted tags. Or use MeterProviderBuilder.SetMaxMetricPointsPerMetricStream to set higher limit.";
@@ -43,7 +44,6 @@ internal sealed class AggregatorStore
     private readonly int exponentialHistogramMaxScale;
     private readonly UpdateLongDelegate updateLongCallback;
     private readonly UpdateDoubleDelegate updateDoubleCallback;
-    private readonly ExemplarFilter exemplarFilter;
     private readonly Func<KeyValuePair<string, object?>[], int, int> lookupAggregatorStore;
 
     private int metricPointIndex = 0;
@@ -73,7 +73,7 @@ internal AggregatorStore(
         this.exponentialHistogramMaxSize = metricStreamIdentity.ExponentialHistogramMaxSize;
         this.exponentialHistogramMaxScale = metricStreamIdentity.ExponentialHistogramMaxScale;
         this.StartTimeExclusive = DateTimeOffset.UtcNow;
-        this.exemplarFilter = exemplarFilter ?? DefaultExemplarFilter;
+        this.ExemplarFilter = exemplarFilter ?? DefaultExemplarFilter;
         if (metricStreamIdentity.TagKeys == null)
         {
             this.updateLongCallback = this.UpdateLong;
@@ -141,7 +141,7 @@ internal bool IsExemplarEnabled()
     {
         // Using this filter to indicate On/Off
         // instead of another separate flag.
-        return this.exemplarFilter is not AlwaysOffExemplarFilter;
+        return this.ExemplarFilter is not AlwaysOffExemplarFilter;
     }
 
     internal void Update(long value, ReadOnlySpan<KeyValuePair<string, object?>> tags)
@@ -931,7 +931,7 @@ private void UpdateLong(long value, ReadOnlySpan<KeyValuePair<string, object?>>
                 if (this.EmitOverflowAttribute)
                 {
                     this.InitializeOverflowTagPointIfNotInitialized();
-                    this.metricPoints[1].Update(value);
+                    this.metricPoints[1].Update(value, tags: default);
                     return;
                 }
                 else
@@ -945,16 +945,7 @@ private void UpdateLong(long value, ReadOnlySpan<KeyValuePair<string, object?>>
                 }
             }
 
-            // TODO: can special case built-in filters to be bit faster.
-            if (this.IsExemplarEnabled()
-                && this.exemplarFilter.ShouldSample(value, tags))
-            {
-                this.metricPoints[index].UpdateAndOfferExemplar(value, tags: default);
-            }
-            else
-            {
-                this.metricPoints[index].Update(value);
-            }
+            this.metricPoints[index].Update(value, tags: default);
         }
         catch (Exception)
         {
@@ -975,7 +966,7 @@ private void UpdateLongCustomTags(long value, ReadOnlySpan<KeyValuePair<string,
                 if (this.EmitOverflowAttribute)
                 {
                     this.InitializeOverflowTagPointIfNotInitialized();
-                    this.metricPoints[1].Update(value);
+                    this.metricPoints[1].Update(value, tags);
                     return;
                 }
                 else
@@ -989,16 +980,7 @@ private void UpdateLongCustomTags(long value, ReadOnlySpan<KeyValuePair<string,
                 }
             }
 
-            // TODO: can special case built-in filters to be bit faster.
-            if (this.IsExemplarEnabled()
-                && this.exemplarFilter.ShouldSample(value, tags))
-            {
-                this.metricPoints[index].UpdateAndOfferExemplar(value, tags);
-            }
-            else
-            {
-                this.metricPoints[index].Update(value);
-            }
+            this.metricPoints[index].Update(value, tags);
         }
         catch (Exception)
         {
@@ -1019,7 +1001,7 @@ private void UpdateDouble(double value, ReadOnlySpan<KeyValuePair<string, object
                 if (this.EmitOverflowAttribute)
                 {
                     this.InitializeOverflowTagPointIfNotInitialized();
-                    this.metricPoints[1].Update(value);
+                    this.metricPoints[1].Update(value, tags: default);
                     return;
                 }
                 else
@@ -1033,16 +1015,7 @@ private void UpdateDouble(double value, ReadOnlySpan<KeyValuePair<string, object
                 }
             }
 
-            // TODO: can special case built-in filters to be bit faster.
-            if (this.IsExemplarEnabled()
-                && this.exemplarFilter.ShouldSample(value, tags))
-            {
-                this.metricPoints[index].UpdateAndOfferExemplar(value, tags: default);
-            }
-            else
-            {
-                this.metricPoints[index].Update(value);
-            }
+            this.metricPoints[index].Update(value, tags: default);
         }
         catch (Exception)
         {
@@ -1063,7 +1036,7 @@ private void UpdateDoubleCustomTags(double value, ReadOnlySpan<KeyValuePair<stri
                 if (this.EmitOverflowAttribute)
                 {
                     this.InitializeOverflowTagPointIfNotInitialized();
-                    this.metricPoints[1].Update(value);
+                    this.metricPoints[1].Update(value, tags);
                     return;
                 }
                 else
@@ -1077,16 +1050,7 @@ private void UpdateDoubleCustomTags(double value, ReadOnlySpan<KeyValuePair<stri
                 }
             }
 
-            // TODO: can special case built-in filters to be bit faster.
-            if (this.IsExemplarEnabled()
-                && this.exemplarFilter.ShouldSample(value, tags))
-            {
-                this.metricPoints[index].UpdateAndOfferExemplar(value, tags);
-            }
-            else
-            {
-                this.metricPoints[index].Update(value);
-            }
+            this.metricPoints[index].Update(value, tags);
         }
         catch (Exception)
         {

src/OpenTelemetry/Metrics/Exemplar/Exemplar.cs

@@ -122,31 +122,13 @@ internal void Reset()
 
     internal readonly bool IsUpdated()
     {
-        if (this.Timestamp == default)
-        {
-            return false;
-        }
-
         if (this.isCriticalSectionOccupied != 0)
         {
-            this.WaitIfUpdatingRare();
+            this.WaitForUpdateToCompleteRare();
+            return true;
         }
 
-        return true;
-    }
-
-    internal readonly void WaitIfUpdatingRare()
-    {
-        var spinWait = default(SpinWait);
-        while (true)
-        {
-            spinWait.SpinOnce();
-
-            if (this.isCriticalSectionOccupied == 0)
-            {
-                return;
-            }
-        }
+        return this.Timestamp != default;
     }
 
     internal readonly void Copy(ref Exemplar destination)
@@ -181,4 +163,14 @@ private void StoreRawTags(ReadOnlySpan<KeyValuePair<string, object?>> tags)
 
         tags.CopyTo(this.tagStorage);
     }
+
+    private readonly void WaitForUpdateToCompleteRare()
+    {
+        var spinWait = default(SpinWait);
+        do
+        {
+            spinWait.SpinOnce();
+        }
+        while (this.isCriticalSectionOccupied != 0);
+    }
 }