core/txpool/legacypool: remove a redundant heap.Init

core/txpool/legacypool/list.go

@@ -160,13 +160,12 @@ func (m *sortedMap) Cap(threshold int) types.Transactions {
 	// Otherwise gather and drop the highest nonce'd transactions
 	var drops types.Transactions
 
-	sort.Sort(*m.index)
+	sort.Sort(*m.index) // the sorted array is a heap, so no need to reheap after deleting tail items
 	for size := len(m.items); size > threshold; size-- {
 		drops = append(drops, m.items[(*m.index)[size-1]])
 		delete(m.items, (*m.index)[size-1])
 	}
 	*m.index = (*m.index)[:threshold]
-	heap.Init(m.index)
 
 	// If we had a cache, shift the back
 	m.cacheMu.Lock()

core/txpool/legacypool/list_test.go

@@ -70,3 +70,25 @@ func BenchmarkListAdd(b *testing.B) {
 		}
 	}
 }
+
+func BenchmarkListCapOneTx(b *testing.B) {
+	// Generate a list of transactions to insert
+	key, _ := crypto.GenerateKey()
+
+	txs := make(types.Transactions, 32)
+	for i := 0; i < len(txs); i++ {
+		txs[i] = transaction(uint64(i), 0, key)
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		list := newList(true)
+		// Insert the transactions in a random order
+		for _, v := range rand.Perm(len(txs)) {
+			list.Add(txs[v], DefaultConfig.PriceBump)
+		}
+		b.StartTimer()
+		list.Cap(list.Len() - 1)
+		b.StopTimer()
+	}
+}