try rwlock for histograms as well

Author: dashpole

sdk/metric/internal/aggregate/exponential_histogram.go

@@ -319,7 +319,7 @@ type expoHistogram[N int64 | float64] struct {
 	newRes   func(attribute.Set) FilteredExemplarReservoir[N]
 	limit    limiter[expoHistogramDataPoint[N]]
 	values   map[attribute.Distinct]*expoHistogramDataPoint[N]
-	valuesMu sync.Mutex
+	valuesMu sync.RWMutex
 
 	start time.Time
 }
@@ -335,9 +335,7 @@ func (e *expoHistogram[N]) measure(
 		return
 	}
 
-	e.valuesMu.Lock()
-	defer e.valuesMu.Unlock()
-
+	e.valuesMu.RLock()
 	attr := e.limit.Attributes(fltrAttr, e.values)
 	v, ok := e.values[attr.Equivalent()]
 	if !ok {
@@ -346,7 +344,10 @@ func (e *expoHistogram[N]) measure(
 
 		e.values[attr.Equivalent()] = v
 	}
+	e.valuesMu.RUnlock()
+	e.valuesMu.Lock()
 	v.record(value)
+	e.valuesMu.Unlock()
 	v.res.Offer(ctx, value, droppedAttr)
 }
 

sdk/metric/internal/aggregate/histogram.go

@@ -50,7 +50,7 @@ type histValues[N int64 | float64] struct {
 	newRes   func(attribute.Set) FilteredExemplarReservoir[N]
 	limit    limiter[buckets[N]]
 	values   map[attribute.Distinct]*buckets[N]
-	valuesMu sync.Mutex
+	valuesMu sync.RWMutex
 }
 
 func newHistValues[N int64 | float64](
@@ -89,8 +89,7 @@ func (s *histValues[N]) measure(
 	// (s.bounds[len(s.bounds)-1], +∞).
 	idx := sort.SearchFloat64s(s.bounds, float64(value))
 
-	s.valuesMu.Lock()
-	defer s.valuesMu.Unlock()
+	s.valuesMu.RLock()
 
 	attr := s.limit.Attributes(fltrAttr, s.values)
 	b, ok := s.values[attr.Equivalent()]
@@ -109,10 +108,13 @@ func (s *histValues[N]) measure(
 		b.min, b.max = value, value
 		s.values[attr.Equivalent()] = b
 	}
+	s.valuesMu.RUnlock()
+	s.valuesMu.Lock()
 	b.bin(idx, value)
 	if !s.noSum {
 		b.sum(value)
 	}
+	s.valuesMu.Unlock()
 	b.res.Offer(ctx, value, droppedAttr)
 }