Address PR comments

core/blockchain.go

@@ -95,7 +95,7 @@ type CacheConfig struct {
 	TrieDirtyLimit      int           // Memory limit (MB) at which to start flushing dirty trie nodes to disk
 	TrieDirtyDisabled   bool          // Whether to disable trie write caching and GC altogether (archive node)
 	TrieTimeLimit       time.Duration // Time limit after which to flush the current in-memory trie to disk
-	ProcessStateDiffs bool
+	ProcessingStateDiffs bool          // Whether statediffs processing should be taken into a account before a trie is pruned
 }
 
 // BlockChain represents the canonical chain given a database with a genesis
@@ -937,14 +937,8 @@ func (bc *BlockChain) WriteBlockWithoutState(block *types.Block, td *big.Int) (e
 }
 
 func (bc *BlockChain) AddToStateDiffProcessedCollection(hash common.Hash) {
-	count, ok := bc.stateDiffsProcessed[hash]
-
-	if ok {
-		count++
-		bc.stateDiffsProcessed[hash] = count
-	} else {
-		bc.stateDiffsProcessed[hash] = 1
-	}
+	count := bc.stateDiffsProcessed[hash]
+	bc.stateDiffsProcessed[hash] = count + 1
 }
 
 // WriteBlockWithState writes the block and all associated state to the database.
@@ -1032,7 +1026,7 @@ func (bc *BlockChain) writeBlockWithState(block *types.Block, receipts []*types.
 					break
 				}
 
-				if bc.cacheConfig.ProcessStateDiffs {
+				if bc.cacheConfig.ProcessingStateDiffs {
 					if !bc.allowedRootToBeDereferenced(root.(common.Hash)) {
 						bc.triegc.Push(root, number)
 						break
@@ -1095,7 +1089,9 @@ func (bc *BlockChain) writeBlockWithState(block *types.Block, receipts []*types.
 	return status, nil
 }
 
-//if we haven't processed the statediff for a given state root and it's child, don't dereference it yet
+// since we need the state tries of the current block and its parent in-memory
+// in order to process statediffs, we should avoid dereferencing roots until
+// its statediff and its child have been processed
 func (bc *BlockChain) allowedRootToBeDereferenced(root common.Hash) bool {
 	diffProcessedForSelfAndChildCount := 2
 	count := bc.stateDiffsProcessed[root]

core/blockchain_test.go

@@ -1816,11 +1816,11 @@ func TestProcessingStateDiffs(t *testing.T) {
 	defaultTrieDirtyCache := 256
 	defaultTrieTimeout := 60 * time.Minute
 	cacheConfig := &CacheConfig{
-		Disabled:          false,
-		TrieCleanLimit:    defaultTrieCleanCache,
-		TrieDirtyLimit:    defaultTrieDirtyCache,
-		TrieTimeLimit:     defaultTrieTimeout,
-		ProcessStateDiffs: true,
+		Disabled:             false,
+		TrieCleanLimit:       defaultTrieCleanCache,
+		TrieDirtyLimit:       defaultTrieDirtyCache,
+		TrieTimeLimit:        defaultTrieTimeout,
+		ProcessingStateDiffs: true,
 	}
 	db := ethdb.NewMemDatabase()
 	genesis := new(Genesis).MustCommit(db)

eth/backend.go

@@ -171,7 +171,7 @@ func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
 			TrieDirtyLimit:      config.TrieDirtyCache,
 			TrieDirtyDisabled:   config.NoPruning,
 			TrieTimeLimit:       config.TrieTimeout,
-			ProcessStateDiffs: config.StateDiff,
+			ProcessingStateDiffs: config.StateDiff,
 		}
 	)
 	eth.blockchain, err = core.NewBlockChain(chainDb, cacheConfig, chainConfig, eth.engine, vmConfig, eth.shouldPreserve)