From 0ef7a76e8401a58637610dd6b6b2736f1ce40bcd Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Tue, 18 Feb 2020 18:11:55 +0300
Subject: [PATCH 1/2] network: batch transactions on broadcast

---
 pkg/network/server.go | 70 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 68 insertions(+), 2 deletions(-)

diff --git a/pkg/network/server.go b/pkg/network/server.go
index 79bf78ec2..86600405d 100644
--- a/pkg/network/server.go
+++ b/pkg/network/server.go
@@ -64,6 +64,8 @@ type (
 		unregister chan peerDrop
 		quit       chan struct{}
 
+		transactions chan *transaction.Transaction
+
 		consensusStarted *atomic.Bool
 
 		log *zap.Logger
@@ -97,6 +99,7 @@ func NewServer(config ServerConfig, chain core.Blockchainer, log *zap.Logger) (*
 		peers:            make(map[Peer]bool),
 		consensusStarted: atomic.NewBool(false),
 		log:              log,
+		transactions:     make(chan *transaction.Transaction, 64),
 	}
 	s.bQueue = newBlockQueue(maxBlockBatch, chain, log, func(b *block.Block) {
 		if s.consensusStarted.Load() {
@@ -174,6 +177,7 @@ func (s *Server) Start(errChan chan error) {
 
 	s.discovery.BackFill(s.Seeds...)
 
+	go s.broadcastTxLoop()
 	go s.bQueue.run()
 	go s.transport.Accept()
 	setServerAndNodeVersions(s.UserAgent, strconv.FormatUint(uint64(s.id), 10))
@@ -602,7 +606,7 @@ func (s *Server) handleTxCmd(tx *transaction.Transaction) error {
 	// in the pool.
 	if s.verifyAndPoolTX(tx) == RelaySucceed {
 		s.consensus.OnTransaction(tx)
-		go s.broadcastTX(tx)
+		s.broadcastTX(tx)
 	}
 	return nil
 }
@@ -828,7 +832,14 @@ func (s *Server) RelayTxn(t *transaction.Transaction) RelayReason {
 
 // broadcastTX broadcasts an inventory message about new transaction.
 func (s *Server) broadcastTX(t *transaction.Transaction) {
-	msg := s.MkMsg(CMDInv, payload.NewInventory(payload.TXType, []util.Uint256{t.Hash()}))
+	select {
+	case s.transactions <- t:
+	case <-s.quit:
+	}
+}
+
+func (s *Server) broadcastTxHashes(hs []util.Uint256) {
+	msg := s.MkMsg(CMDInv, payload.NewInventory(payload.TXType, hs))
 
 	// We need to filter out non-relaying nodes, so plain broadcast
 	// functions don't fit here.
@@ -836,3 +847,58 @@ func (s *Server) broadcastTX(t *transaction.Transaction) {
 		return p.Handshaked() && p.Version().Relay
 	})
 }
+
+// broadcastTxLoop is a loop for batching and sending
+// transactions hashes in an INV payload.
+func (s *Server) broadcastTxLoop() {
+	const (
+		batchTime = time.Millisecond * 50
+		batchSize = 32
+	)
+
+	txs := make([]util.Uint256, 0, batchSize)
+	var timer *time.Timer
+
+	timerCh := func() <-chan time.Time {
+		if timer == nil {
+			return nil
+		}
+		return timer.C
+	}
+
+	broadcast := func() {
+		s.broadcastTxHashes(txs)
+		txs = txs[:0]
+		if timer != nil {
+			timer.Stop()
+		}
+	}
+
+	for {
+		select {
+		case <-s.quit:
+		loop:
+			for {
+				select {
+				case <-s.transactions:
+				default:
+					break loop
+				}
+			}
+			return
+		case <-timerCh():
+			if len(txs) > 0 {
+				broadcast()
+			}
+		case tx := <-s.transactions:
+			if len(txs) == 0 {
+				timer = time.NewTimer(batchTime)
+			}
+
+			txs = append(txs, tx.Hash())
+			if len(txs) == batchSize {
+				broadcast()
+			}
+		}
+	}
+}

From cbf26bac8329d590d88ee20bd7d00b8dd1d3aa8f Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Wed, 19 Feb 2020 16:10:40 +0300
Subject: [PATCH 2/2] mempool: do not allocate new slice for verified
 transactions

Because transactions a iterated in an increasing order,
we can filter slice in-place.
---
 pkg/core/mempool/mem_pool.go | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/pkg/core/mempool/mem_pool.go b/pkg/core/mempool/mem_pool.go
index e0371fe2a..09b30bc29 100644
--- a/pkg/core/mempool/mem_pool.go
+++ b/pkg/core/mempool/mem_pool.go
@@ -260,9 +260,9 @@ func (mp *Pool) Remove(hash util.Uint256) {
 // drop part of the mempool that is now invalid after the block acceptance.
 func (mp *Pool) RemoveStale(isOK func(*transaction.Transaction) bool) {
 	mp.lock.Lock()
-	// We expect a lot of changes, so it's easier to allocate a new slice
-	// rather than move things in an old one.
-	newVerifiedTxes := make([]*item, 0, mp.capacity)
+	// We can reuse already allocated slice
+	// because items are iterated one-by-one in increasing order.
+	newVerifiedTxes := mp.verifiedTxes[:0]
 	newInputs := mp.inputs[:0]
 	newClaims := mp.claims[:0]
 	for _, itm := range mp.verifiedTxes {