core/txpool/legacypool: remove a redundant heap.Init (#28910)

Co-authored-by: Martin HS <martin@swende.se>
Co-authored-by: Felix Lange <fjl@twurst.com>

core/txpool/legacypool/list.go

@@ -28,6 +28,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/holiman/uint256"
+	"golang.org/x/exp/slices"
 )
 
 // nonceHeap is a heap.Interface implementation over 64bit unsigned integers for
@@ -160,14 +161,14 @@ 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)
+	slices.Sort(*m.index)
 	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)
+	// The sorted m.index slice is still a valid heap, so there is no need to
+	// reheap after deleting tail items.
 
 	// If we had a cache, shift the back
 	m.cacheMu.Lock()

core/txpool/legacypool/list_test.go

@@ -87,3 +87,25 @@ 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()
+	}
+}