core: use a wrapped map to remove contention in `TxPool.Get`. (#16670)

* core: use a wrapped `map` and `sync.RWMutex` for `TxPool.all` to remove contention in `TxPool.Get`.

* core: Remove redundant `txLookup.Find` and improve comments on txLookup methods.

3 files changed, 132 insertions, 69 deletions

diff --git a/core/tx_list.go b/core/tx_list.go
index ea6ee7019..287dda4c3 100644
--- a/core/tx_list.go
+++ b/core/tx_list.go
@@ -397,13 +397,13 @@ func (h *priceHeap) Pop() interface{} {
 // txPricedList is a price-sorted heap to allow operating on transactions pool
 // contents in a price-incrementing way.
 type txPricedList struct {
-	all    *map[common.Hash]*types.Transaction // Pointer to the map of all transactions
-	items  *priceHeap                          // Heap of prices of all the stored transactions
-	stales int                                 // Number of stale price points to (re-heap trigger)
+	all    *txLookup  // Pointer to the map of all transactions
+	items  *priceHeap // Heap of prices of all the stored transactions
+	stales int        // Number of stale price points to (re-heap trigger)
 }
 
 // newTxPricedList creates a new price-sorted transaction heap.
-func newTxPricedList(all *map[common.Hash]*types.Transaction) *txPricedList {
+func newTxPricedList(all *txLookup) *txPricedList {
 	return &txPricedList{
 		all:   all,
 		items: new(priceHeap),
@@ -425,12 +425,13 @@ func (l *txPricedList) Removed() {
 		return
 	}
 	// Seems we've reached a critical number of stale transactions, reheap
-	reheap := make(priceHeap, 0, len(*l.all))
+	reheap := make(priceHeap, 0, l.all.Count())
 
 	l.stales, l.items = 0, &reheap
-	for _, tx := range *l.all {
+	l.all.Range(func(hash common.Hash, tx *types.Transaction) bool {
 		*l.items = append(*l.items, tx)
-	}
+		return true
+	})
 	heap.Init(l.items)
 }
 
@@ -443,7 +444,7 @@ func (l *txPricedList) Cap(threshold *big.Int, local *accountSet) types.Transact
 	for len(*l.items) > 0 {
 		// Discard stale transactions if found during cleanup
 		tx := heap.Pop(l.items).(*types.Transaction)
-		if _, ok := (*l.all)[tx.Hash()]; !ok {
+		if l.all.Get(tx.Hash()) == nil {
 			l.stales--
 			continue
 		}
@@ -475,7 +476,7 @@ func (l *txPricedList) Underpriced(tx *types.Transaction, local *accountSet) boo
 	// Discard stale price points if found at the heap start
 	for len(*l.items) > 0 {
 		head := []*types.Transaction(*l.items)[0]
-		if _, ok := (*l.all)[head.Hash()]; !ok {
+		if l.all.Get(head.Hash()) == nil {
 			l.stales--
 			heap.Pop(l.items)
 			continue
@@ -500,7 +501,7 @@ func (l *txPricedList) Discard(count int, local *accountSet) types.Transactions
 	for len(*l.items) > 0 && count > 0 {
 		// Discard stale transactions if found during cleanup
 		tx := heap.Pop(l.items).(*types.Transaction)
-		if _, ok := (*l.all)[tx.Hash()]; !ok {
+		if l.all.Get(tx.Hash()) == nil {
 			l.stales--
 			continue
 		}
diff --git a/core/tx_pool.go b/core/tx_pool.go
index f89e11441..1c9516b1b 100644
--- a/core/tx_pool.go
+++ b/core/tx_pool.go
@@ -200,11 +200,11 @@ type TxPool struct {
 	locals  *accountSet // Set of local transaction to exempt from eviction rules
 	journal *txJournal  // Journal of local transaction to back up to disk
 
-	pending map[common.Address]*txList         // All currently processable transactions
-	queue   map[common.Address]*txList         // Queued but non-processable transactions
-	beats   map[common.Address]time.Time       // Last heartbeat from each known account
-	all     map[common.Hash]*types.Transaction // All transactions to allow lookups
-	priced  *txPricedList                      // All transactions sorted by price
+	pending map[common.Address]*txList   // All currently processable transactions
+	queue   map[common.Address]*txList   // Queued but non-processable transactions
+	beats   map[common.Address]time.Time // Last heartbeat from each known account
+	all     *txLookup                    // All transactions to allow lookups
+	priced  *txPricedList                // All transactions sorted by price
 
 	wg sync.WaitGroup // for shutdown sync
 
@@ -226,12 +226,12 @@ func NewTxPool(config TxPoolConfig, chainconfig *params.ChainConfig, chain block
 		pending:     make(map[common.Address]*txList),
 		queue:       make(map[common.Address]*txList),
 		beats:       make(map[common.Address]time.Time),
-		all:         make(map[common.Hash]*types.Transaction),
+		all:         newTxLookup(),
 		chainHeadCh: make(chan ChainHeadEvent, chainHeadChanSize),
 		gasPrice:    new(big.Int).SetUint64(config.PriceLimit),
 	}
 	pool.locals = newAccountSet(pool.signer)
-	pool.priced = newTxPricedList(&pool.all)
+	pool.priced = newTxPricedList(pool.all)
 	pool.reset(nil, chain.CurrentBlock().Header())
 
 	// If local transactions and journaling is enabled, load from disk
@@ -605,7 +605,7 @@ func (pool *TxPool) validateTx(tx *types.Transaction, local bool) error {
 func (pool *TxPool) add(tx *types.Transaction, local bool) (bool, error) {
 	// If the transaction is already known, discard it
 	hash := tx.Hash()
-	if pool.all[hash] != nil {
+	if pool.all.Get(hash) != nil {
 		log.Trace("Discarding already known transaction", "hash", hash)
 		return false, fmt.Errorf("known transaction: %x", hash)
 	}
@@ -616,7 +616,7 @@ func (pool *TxPool) add(tx *types.Transaction, local bool) (bool, error) {
 		return false, err
 	}
 	// If the transaction pool is full, discard underpriced transactions
-	if uint64(len(pool.all)) >= pool.config.GlobalSlots+pool.config.GlobalQueue {
+	if uint64(pool.all.Count()) >= pool.config.GlobalSlots+pool.config.GlobalQueue {
 		// If the new transaction is underpriced, don't accept it
 		if !local && pool.priced.Underpriced(tx, pool.locals) {
 			log.Trace("Discarding underpriced transaction", "hash", hash, "price", tx.GasPrice())
@@ -624,7 +624,7 @@ func (pool *TxPool) add(tx *types.Transaction, local bool) (bool, error) {
 			return false, ErrUnderpriced
 		}
 		// New transaction is better than our worse ones, make room for it
-		drop := pool.priced.Discard(len(pool.all)-int(pool.config.GlobalSlots+pool.config.GlobalQueue-1), pool.locals)
+		drop := pool.priced.Discard(pool.all.Count()-int(pool.config.GlobalSlots+pool.config.GlobalQueue-1), pool.locals)
 		for _, tx := range drop {
 			log.Trace("Discarding freshly underpriced transaction", "hash", tx.Hash(), "price", tx.GasPrice())
 			underpricedTxCounter.Inc(1)
@@ -642,11 +642,11 @@ func (pool *TxPool) add(tx *types.Transaction, local bool) (bool, error) {
 		}
 		// New transaction is better, replace old one
 		if old != nil {
-			delete(pool.all, old.Hash())
+			pool.all.Remove(old.Hash())
 			pool.priced.Removed()
 			pendingReplaceCounter.Inc(1)
 		}
-		pool.all[tx.Hash()] = tx
+		pool.all.Add(tx)
 		pool.priced.Put(tx)
 		pool.journalTx(from, tx)
 
@@ -689,12 +689,12 @@ func (pool *TxPool) enqueueTx(hash common.Hash, tx *types.Transaction) (bool, er
 	}
 	// Discard any previous transaction and mark this
 	if old != nil {
-		delete(pool.all, old.Hash())
+		pool.all.Remove(old.Hash())
 		pool.priced.Removed()
 		queuedReplaceCounter.Inc(1)
 	}
-	if pool.all[hash] == nil {
-		pool.all[hash] = tx
+	if pool.all.Get(hash) == nil {
+		pool.all.Add(tx)
 		pool.priced.Put(tx)
 	}
 	return old != nil, nil
@@ -726,7 +726,7 @@ func (pool *TxPool) promoteTx(addr common.Address, hash common.Hash, tx *types.T
 	inserted, old := list.Add(tx, pool.config.PriceBump)
 	if !inserted {
 		// An older transaction was better, discard this
-		delete(pool.all, hash)
+		pool.all.Remove(hash)
 		pool.priced.Removed()
 
 		pendingDiscardCounter.Inc(1)
@@ -734,14 +734,14 @@ func (pool *TxPool) promoteTx(addr common.Address, hash common.Hash, tx *types.T
 	}
 	// Otherwise discard any previous transaction and mark this
 	if old != nil {
-		delete(pool.all, old.Hash())
+		pool.all.Remove(old.Hash())
 		pool.priced.Removed()
 
 		pendingReplaceCounter.Inc(1)
 	}
 	// Failsafe to work around direct pending inserts (tests)
-	if pool.all[hash] == nil {
-		pool.all[hash] = tx
+	if pool.all.Get(hash) == nil {
+		pool.all.Add(tx)
 		pool.priced.Put(tx)
 	}
 	// Set the potentially new pending nonce and notify any subsystems of the new tx
@@ -840,7 +840,7 @@ func (pool *TxPool) Status(hashes []common.Hash) []TxStatus {
 
 	status := make([]TxStatus, len(hashes))
 	for i, hash := range hashes {
-		if tx := pool.all[hash]; tx != nil {
+		if tx := pool.all.Get(hash); tx != nil {
 			from, _ := types.Sender(pool.signer, tx) // already validated
 			if pool.pending[from] != nil && pool.pending[from].txs.items[tx.Nonce()] != nil {
 				status[i] = TxStatusPending
@@ -855,24 +855,21 @@ func (pool *TxPool) Status(hashes []common.Hash) []TxStatus {
 // Get returns a transaction if it is contained in the pool
 // and nil otherwise.
 func (pool *TxPool) Get(hash common.Hash) *types.Transaction {
-	pool.mu.RLock()
-	defer pool.mu.RUnlock()
-
-	return pool.all[hash]
+	return pool.all.Get(hash)
 }
 
 // removeTx removes a single transaction from the queue, moving all subsequent
 // transactions back to the future queue.
 func (pool *TxPool) removeTx(hash common.Hash, outofbound bool) {
 	// Fetch the transaction we wish to delete
-	tx, ok := pool.all[hash]
-	if !ok {
+	tx := pool.all.Get(hash)
+	if tx == nil {
 		return
 	}
 	addr, _ := types.Sender(pool.signer, tx) // already validated during insertion
 
 	// Remove it from the list of known transactions
-	delete(pool.all, hash)
+	pool.all.Remove(hash)
 	if outofbound {
 		pool.priced.Removed()
 	}
@@ -928,7 +925,7 @@ func (pool *TxPool) promoteExecutables(accounts []common.Address) {
 		for _, tx := range list.Forward(pool.currentState.GetNonce(addr)) {
 			hash := tx.Hash()
 			log.Trace("Removed old queued transaction", "hash", hash)
-			delete(pool.all, hash)
+			pool.all.Remove(hash)
 			pool.priced.Removed()
 		}
 		// Drop all transactions that are too costly (low balance or out of gas)
@@ -936,7 +933,7 @@ func (pool *TxPool) promoteExecutables(accounts []common.Address) {
 		for _, tx := range drops {
 			hash := tx.Hash()
 			log.Trace("Removed unpayable queued transaction", "hash", hash)
-			delete(pool.all, hash)
+			pool.all.Remove(hash)
 			pool.priced.Removed()
 			queuedNofundsCounter.Inc(1)
 		}
@@ -952,7 +949,7 @@ func (pool *TxPool) promoteExecutables(accounts []common.Address) {
 		if !pool.locals.contains(addr) {
 			for _, tx := range list.Cap(int(pool.config.AccountQueue)) {
 				hash := tx.Hash()
-				delete(pool.all, hash)
+				pool.all.Remove(hash)
 				pool.priced.Removed()
 				queuedRateLimitCounter.Inc(1)
 				log.Trace("Removed cap-exceeding queued transaction", "hash", hash)
@@ -1001,7 +998,7 @@ func (pool *TxPool) promoteExecutables(accounts []common.Address) {
 						for _, tx := range list.Cap(list.Len() - 1) {
 							// Drop the transaction from the global pools too
 							hash := tx.Hash()
-							delete(pool.all, hash)
+							pool.all.Remove(hash)
 							pool.priced.Removed()
 
 							// Update the account nonce to the dropped transaction
@@ -1023,7 +1020,7 @@ func (pool *TxPool) promoteExecutables(accounts []common.Address) {
 					for _, tx := range list.Cap(list.Len() - 1) {
 						// Drop the transaction from the global pools too
 						hash := tx.Hash()
-						delete(pool.all, hash)
+						pool.all.Remove(hash)
 						pool.priced.Removed()
 
 						// Update the account nonce to the dropped transaction
@@ -1092,7 +1089,7 @@ func (pool *TxPool) demoteUnexecutables() {
 		for _, tx := range list.Forward(nonce) {
 			hash := tx.Hash()
 			log.Trace("Removed old pending transaction", "hash", hash)
-			delete(pool.all, hash)
+			pool.all.Remove(hash)
 			pool.priced.Removed()
 		}
 		// Drop all transactions that are too costly (low balance or out of gas), and queue any invalids back for later
@@ -1100,7 +1097,7 @@ func (pool *TxPool) demoteUnexecutables() {
 		for _, tx := range drops {
 			hash := tx.Hash()
 			log.Trace("Removed unpayable pending transaction", "hash", hash)
-			delete(pool.all, hash)
+			pool.all.Remove(hash)
 			pool.priced.Removed()
 			pendingNofundsCounter.Inc(1)
 		}
@@ -1172,3 +1169,68 @@ func (as *accountSet) containsTx(tx *types.Transaction) bool {
 func (as *accountSet) add(addr common.Address) {
 	as.accounts[addr] = struct{}{}
 }
+
+// txLookup is used internally by TxPool to track transactions while allowing lookup without
+// mutex contention.
+//
+// Note, although this type is properly protected against concurrent access, it
+// is **not** a type that should ever be mutated or even exposed outside of the
+// transaction pool, since its internal state is tightly coupled with the pools
+// internal mechanisms. The sole purpose of the type is to permit out-of-bound
+// peeking into the pool in TxPool.Get without having to acquire the widely scoped
+// TxPool.mu mutex.
+type txLookup struct {
+	all  map[common.Hash]*types.Transaction
+	lock sync.RWMutex
+}
+
+// newTxLookup returns a new txLookup structure.
+func newTxLookup() *txLookup {
+	return &txLookup{
+		all: make(map[common.Hash]*types.Transaction),
+	}
+}
+
+// Range calls f on each key and value present in the map.
+func (t *txLookup) Range(f func(hash common.Hash, tx *types.Transaction) bool) {
+	t.lock.RLock()
+	defer t.lock.RUnlock()
+
+	for key, value := range t.all {
+		if !f(key, value) {
+			break
+		}
+	}
+}
+
+// Get returns a transaction if it exists in the lookup, or nil if not found.
+func (t *txLookup) Get(hash common.Hash) *types.Transaction {
+	t.lock.RLock()
+	defer t.lock.RUnlock()
+
+	return t.all[hash]
+}
+
+// Count returns the current number of items in the lookup.
+func (t *txLookup) Count() int {
+	t.lock.RLock()
+	defer t.lock.RUnlock()
+
+	return len(t.all)
+}
+
+// Add adds a transaction to the lookup.
+func (t *txLookup) Add(tx *types.Transaction) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	t.all[tx.Hash()] = tx
+}
+
+// Remove removes a transaction from the lookup.
+func (t *txLookup) Remove(hash common.Hash) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	delete(t.all, hash)
+}
diff --git a/core/tx_pool_test.go b/core/tx_pool_test.go
index 25993c258..5a5920544 100644
--- a/core/tx_pool_test.go
+++ b/core/tx_pool_test.go
@@ -94,7 +94,7 @@ func validateTxPoolInternals(pool *TxPool) error {
 
 	// Ensure the total transaction set is consistent with pending + queued
 	pending, queued := pool.stats()
-	if total := len(pool.all); total != pending+queued {
+	if total := pool.all.Count(); total != pending+queued {
 		return fmt.Errorf("total transaction count %d != %d pending + %d queued", total, pending, queued)
 	}
 	if priced := pool.priced.items.Len() - pool.priced.stales; priced != pending+queued {
@@ -401,8 +401,8 @@ func TestTransactionDoubleNonce(t *testing.T) {
 		t.Errorf("transaction mismatch: have %x, want %x", tx.Hash(), tx2.Hash())
 	}
 	// Ensure the total transaction count is correct
-	if len(pool.all) != 1 {
-		t.Error("expected 1 total transactions, got", len(pool.all))
+	if pool.all.Count() != 1 {
+		t.Error("expected 1 total transactions, got", pool.all.Count())
 	}
 }
 
@@ -424,8 +424,8 @@ func TestTransactionMissingNonce(t *testing.T) {
 	if pool.queue[addr].Len() != 1 {
 		t.Error("expected 1 queued transaction, got", pool.queue[addr].Len())
 	}
-	if len(pool.all) != 1 {
-		t.Error("expected 1 total transactions, got", len(pool.all))
+	if pool.all.Count() != 1 {
+		t.Error("expected 1 total transactions, got", pool.all.Count())
 	}
 }
 
@@ -488,8 +488,8 @@ func TestTransactionDropping(t *testing.T) {
 	if pool.queue[account].Len() != 3 {
 		t.Errorf("queued transaction mismatch: have %d, want %d", pool.queue[account].Len(), 3)
 	}
-	if len(pool.all) != 6 {
-		t.Errorf("total transaction mismatch: have %d, want %d", len(pool.all), 6)
+	if pool.all.Count() != 6 {
+		t.Errorf("total transaction mismatch: have %d, want %d", pool.all.Count(), 6)
 	}
 	pool.lockedReset(nil, nil)
 	if pool.pending[account].Len() != 3 {
@@ -498,8 +498,8 @@ func TestTransactionDropping(t *testing.T) {
 	if pool.queue[account].Len() != 3 {
 		t.Errorf("queued transaction mismatch: have %d, want %d", pool.queue[account].Len(), 3)
 	}
-	if len(pool.all) != 6 {
-		t.Errorf("total transaction mismatch: have %d, want %d", len(pool.all), 6)
+	if pool.all.Count() != 6 {
+		t.Errorf("total transaction mismatch: have %d, want %d", pool.all.Count(), 6)
 	}
 	// Reduce the balance of the account, and check that invalidated transactions are dropped
 	pool.currentState.AddBalance(account, big.NewInt(-650))
@@ -523,8 +523,8 @@ func TestTransactionDropping(t *testing.T) {
 	if _, ok := pool.queue[account].txs.items[tx12.Nonce()]; ok {
 		t.Errorf("out-of-fund queued transaction present: %v", tx11)
 	}
-	if len(pool.all) != 4 {
-		t.Errorf("total transaction mismatch: have %d, want %d", len(pool.all), 4)
+	if pool.all.Count() != 4 {
+		t.Errorf("total transaction mismatch: have %d, want %d", pool.all.Count(), 4)
 	}
 	// Reduce the block gas limit, check that invalidated transactions are dropped
 	pool.chain.(*testBlockChain).gasLimit = 100
@@ -542,8 +542,8 @@ func TestTransactionDropping(t *testing.T) {
 	if _, ok := pool.queue[account].txs.items[tx11.Nonce()]; ok {
 		t.Errorf("over-gased queued transaction present: %v", tx11)
 	}
-	if len(pool.all) != 2 {
-		t.Errorf("total transaction mismatch: have %d, want %d", len(pool.all), 2)
+	if pool.all.Count() != 2 {
+		t.Errorf("total transaction mismatch: have %d, want %d", pool.all.Count(), 2)
 	}
 }
 
@@ -596,8 +596,8 @@ func TestTransactionPostponing(t *testing.T) {
 	if len(pool.queue) != 0 {
 		t.Errorf("queued accounts mismatch: have %d, want %d", len(pool.queue), 0)
 	}
-	if len(pool.all) != len(txs) {
-		t.Errorf("total transaction mismatch: have %d, want %d", len(pool.all), len(txs))
+	if pool.all.Count() != len(txs) {
+		t.Errorf("total transaction mismatch: have %d, want %d", pool.all.Count(), len(txs))
 	}
 	pool.lockedReset(nil, nil)
 	if pending := pool.pending[accs[0]].Len() + pool.pending[accs[1]].Len(); pending != len(txs) {
@@ -606,8 +606,8 @@ func TestTransactionPostponing(t *testing.T) {
 	if len(pool.queue) != 0 {
 		t.Errorf("queued accounts mismatch: have %d, want %d", len(pool.queue), 0)
 	}
-	if len(pool.all) != len(txs) {
-		t.Errorf("total transaction mismatch: have %d, want %d", len(pool.all), len(txs))
+	if pool.all.Count() != len(txs) {
+		t.Errorf("total transaction mismatch: have %d, want %d", pool.all.Count(), len(txs))
 	}
 	// Reduce the balance of the account, and check that transactions are reorganised
 	for _, addr := range accs {
@@ -656,8 +656,8 @@ func TestTransactionPostponing(t *testing.T) {
 			}
 		}
 	}
-	if len(pool.all) != len(txs)/2 {
-		t.Errorf("total transaction mismatch: have %d, want %d", len(pool.all), len(txs)/2)
+	if pool.all.Count() != len(txs)/2 {
+		t.Errorf("total transaction mismatch: have %d, want %d", pool.all.Count(), len(txs)/2)
 	}
 }
 
@@ -748,8 +748,8 @@ func TestTransactionQueueAccountLimiting(t *testing.T) {
 			}
 		}
 	}
-	if len(pool.all) != int(testTxPoolConfig.AccountQueue) {
-		t.Errorf("total transaction mismatch: have %d, want %d", len(pool.all), testTxPoolConfig.AccountQueue)
+	if pool.all.Count() != int(testTxPoolConfig.AccountQueue) {
+		t.Errorf("total transaction mismatch: have %d, want %d", pool.all.Count(), testTxPoolConfig.AccountQueue)
 	}
 }
 
@@ -942,8 +942,8 @@ func TestTransactionPendingLimiting(t *testing.T) {
 			t.Errorf("tx %d: queue size mismatch: have %d, want %d", i, pool.queue[account].Len(), 0)
 		}
 	}
-	if len(pool.all) != int(testTxPoolConfig.AccountQueue+5) {
-		t.Errorf("total transaction mismatch: have %d, want %d", len(pool.all), testTxPoolConfig.AccountQueue+5)
+	if pool.all.Count() != int(testTxPoolConfig.AccountQueue+5) {
+		t.Errorf("total transaction mismatch: have %d, want %d", pool.all.Count(), testTxPoolConfig.AccountQueue+5)
 	}
 	if err := validateEvents(events, int(testTxPoolConfig.AccountQueue+5)); err != nil {
 		t.Fatalf("event firing failed: %v", err)
@@ -993,8 +993,8 @@ func testTransactionLimitingEquivalency(t *testing.T, origin uint64) {
 	if len(pool1.queue) != len(pool2.queue) {
 		t.Errorf("queued transaction count mismatch: one-by-one algo: %d, batch algo: %d", len(pool1.queue), len(pool2.queue))
 	}
-	if len(pool1.all) != len(pool2.all) {
-		t.Errorf("total transaction count mismatch: one-by-one algo %d, batch algo %d", len(pool1.all), len(pool2.all))
+	if pool1.all.Count() != pool2.all.Count() {
+		t.Errorf("total transaction count mismatch: one-by-one algo %d, batch algo %d", pool1.all.Count(), pool2.all.Count())
 	}
 	if err := validateTxPoolInternals(pool1); err != nil {
 		t.Errorf("pool 1 internal state corrupted: %v", err)