From 2a1fc3d155870ba2e42f108a232b4b6a3ad9d939 Mon Sep 17 00:00:00 2001
From: Ryan Schneider <ryanleeschneider@gmail.com>
Date: Mon, 16 Apr 2018 00:56:20 -0700
Subject: [PATCH] miner: remove contention on currentMu for pending data
 retrievals (#16497)

---
 miner/worker.go | 51 ++++++++++++++++++++++++++++++++-----------------
 1 file changed, 33 insertions(+), 18 deletions(-)

diff --git a/miner/worker.go b/miner/worker.go
index 15395ae0b9..48b0b27652 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -117,6 +117,10 @@ type worker struct {
 	currentMu sync.Mutex
 	current   *Work
 
+	snapshotMu    sync.RWMutex
+	snapshotBlock *types.Block
+	snapshotState *state.StateDB
+
 	uncleMu        sync.Mutex
 	possibleUncles map[common.Hash]*types.Block
 
@@ -171,32 +175,28 @@ func (self *worker) setExtra(extra []byte) {
 }
 
 func (self *worker) pending() (*types.Block, *state.StateDB) {
+	if atomic.LoadInt32(&self.mining) == 0 {
+		// return a snapshot to avoid contention on currentMu mutex
+		self.snapshotMu.RLock()
+		defer self.snapshotMu.RUnlock()
+		return self.snapshotBlock, self.snapshotState.Copy()
+	}
+
 	self.currentMu.Lock()
 	defer self.currentMu.Unlock()
-
-	if atomic.LoadInt32(&self.mining) == 0 {
-		return types.NewBlock(
-			self.current.header,
-			self.current.txs,
-			nil,
-			self.current.receipts,
-		), self.current.state.Copy()
-	}
 	return self.current.Block, self.current.state.Copy()
 }
 
 func (self *worker) pendingBlock() *types.Block {
+	if atomic.LoadInt32(&self.mining) == 0 {
+		// return a snapshot to avoid contention on currentMu mutex
+		self.snapshotMu.RLock()
+		defer self.snapshotMu.RUnlock()
+		return self.snapshotBlock
+	}
+
 	self.currentMu.Lock()
 	defer self.currentMu.Unlock()
-
-	if atomic.LoadInt32(&self.mining) == 0 {
-		return types.NewBlock(
-			self.current.header,
-			self.current.txs,
-			nil,
-			self.current.receipts,
-		)
-	}
 	return self.current.Block
 }
 
@@ -268,6 +268,7 @@ func (self *worker) update() {
 				txset := types.NewTransactionsByPriceAndNonce(self.current.signer, txs)
 
 				self.current.commitTransactions(self.mux, txset, self.chain, self.coinbase)
+				self.updateSnapshot()
 				self.currentMu.Unlock()
 			} else {
 				// If we're mining, but nothing is being processed, wake on new transactions
@@ -489,6 +490,7 @@ func (self *worker) commitNewWork() {
 		self.unconfirmed.Shift(work.Block.NumberU64() - 1)
 	}
 	self.push(work)
+	self.updateSnapshot()
 }
 
 func (self *worker) commitUncle(work *Work, uncle *types.Header) error {
@@ -506,6 +508,19 @@ func (self *worker) commitUncle(work *Work, uncle *types.Header) error {
 	return nil
 }
 
+func (self *worker) updateSnapshot() {
+	self.snapshotMu.Lock()
+	defer self.snapshotMu.Unlock()
+
+	self.snapshotBlock = types.NewBlock(
+		self.current.header,
+		self.current.txs,
+		nil,
+		self.current.receipts,
+	)
+	self.snapshotState = self.current.state.Copy()
+}
+
 func (env *Work) commitTransactions(mux *event.TypeMux, txs *types.TransactionsByPriceAndNonce, bc *core.BlockChain, coinbase common.Address) {
 	gp := new(core.GasPool).AddGas(env.header.GasLimit)