Replace weighted semaphore with channel

x/merkledb/db.go

@@ -15,7 +15,6 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"go.opentelemetry.io/otel/attribute"
 	"golang.org/x/exp/maps"
-	"golang.org/x/sync/semaphore"
 
 	"github.com/ava-labs/avalanchego/database"
 	"github.com/ava-labs/avalanchego/ids"
@@ -218,7 +217,7 @@ type merkleDB struct {
 
 	// calculateNodeIDsSema controls the number of goroutines inside
 	// [calculateNodeIDsHelper] at any given time.
-	calculateNodeIDsSema *semaphore.Weighted
+	calculateNodeIDsSema semaphore
 
 	tokenSize int
 }
@@ -274,7 +273,7 @@ func newDatabase(
 		debugTracer:          getTracerIfEnabled(config.TraceLevel, DebugTrace, config.Tracer),
 		infoTracer:           getTracerIfEnabled(config.TraceLevel, InfoTrace, config.Tracer),
 		childViews:           make([]*view, 0, defaultPreallocationSize),
-		calculateNodeIDsSema: semaphore.NewWeighted(int64(rootGenConcurrency)),
+		calculateNodeIDsSema: make(semaphore, rootGenConcurrency),
 		tokenSize:            BranchFactorToTokenSize[config.BranchFactor],
 	}
 

x/merkledb/semaphore.go

@@ -0,0 +1,27 @@
+// Copyright (C) 2019-2024, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package merkledb
+
+type semaphore chan struct{}
+
+func (s semaphore) Acquire() {
+	s <- struct{}{}
+}
+
+func (s semaphore) TryAcquire() bool {
+	select {
+	case s <- struct{}{}:
+		return true
+	default:
+		return false
+	}
+}
+
+func (s semaphore) Release() {
+	select {
+	case <-s:
+	default:
+		panic("release of unacquired semaphore")
+	}
+}

x/merkledb/semaphore_test.go

@@ -0,0 +1,46 @@
+// Copyright (C) 2019-2024, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package merkledb
+
+import "testing"
+
+func Benchmark_Semaphore_Acquire(b *testing.B) {
+	s := make(semaphore, b.N)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		s.Acquire()
+	}
+}
+
+func Benchmark_Semaphore_Release(b *testing.B) {
+	s := make(semaphore, b.N)
+	for i := 0; i < b.N; i++ {
+		s.Acquire()
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		s.Release()
+	}
+}
+
+func Benchmark_Semaphore_TryAcquire_Success(b *testing.B) {
+	s := make(semaphore, b.N)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		s.TryAcquire()
+	}
+}
+
+func Benchmark_Semaphore_TryAcquire_Failure(b *testing.B) {
+	s := make(semaphore, 1)
+	s.Acquire()
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		s.TryAcquire()
+	}
+}

x/merkledb/view.go

@@ -244,9 +244,9 @@ func (v *view) calculateNodeIDs(ctx context.Context) error {
 		}
 
 		if !v.root.IsNothing() {
-			_ = v.db.calculateNodeIDsSema.Acquire(context.Background(), 1)
+			v.db.calculateNodeIDsSema.Acquire()
 			v.changes.rootID = v.calculateNodeIDsHelper(v.root.Value())
-			v.db.calculateNodeIDsSema.Release(1)
+			v.db.calculateNodeIDsSema.Release()
 		} else {
 			v.changes.rootID = ids.Empty
 		}
@@ -282,11 +282,11 @@ func (v *view) calculateNodeIDsHelper(n *node) ids.ID {
 		childEntry.hasValue = childNodeChange.after.hasValue()
 
 		// Try updating the child and its descendants in a goroutine.
-		if ok := v.db.calculateNodeIDsSema.TryAcquire(1); ok {
+		if v.db.calculateNodeIDsSema.TryAcquire() {
 			wg.Add(1)
 			go func() {
 				childEntry.id = v.calculateNodeIDsHelper(childNodeChange.after)
-				v.db.calculateNodeIDsSema.Release(1)
+				v.db.calculateNodeIDsSema.Release()
 				wg.Done()
 			}()
 		} else {