refactor trie_prefetcher to be similar to upstream structurally (#1395)

Co-authored-by: Quentin McGaw <quentin.mcgaw@gmail.com>
Co-authored-by: Arran Schlosberg <519948+ARR4N@users.noreply.github.com>

RELEASES.md

@@ -2,11 +2,15 @@
 
 ## Pending Release
 
-## Updates
+* Refactored trie_prefetcher.go to be structurally similar to upstream.
+
+## [v0.7.0](https://github.com/ava-labs/subnet-evm/releases/tag/v0.7.0)
+
+### Updates
 
 - Changed default write option from `Sync` to `NoSync` in PebbleDB
 
-## Fixes
+### Fixes
 
 - Fixed database close on shutdown
 

core/blockchain.go

@@ -1349,16 +1349,6 @@ func (bc *BlockChain) insertBlock(block *types.Block, writes bool) error {
 	blockContentValidationTimer.Inc(time.Since(substart).Milliseconds())
 
 	// No validation errors for the block
-	var activeState *state.StateDB
-	defer func() {
-		// The chain importer is starting and stopping trie prefetchers. If a bad
-		// block or other error is hit however, an early return may not properly
-		// terminate the background threads. This defer ensures that we clean up
-		// and dangling prefetcher, without deferring each and holding on live refs.
-		if activeState != nil {
-			activeState.StopPrefetcher()
-		}
-	}()
 
 	// Retrieve the parent block to determine which root to build state on
 	substart = time.Now()
@@ -1377,8 +1367,8 @@ func (bc *BlockChain) insertBlock(block *types.Block, writes bool) error {
 	blockStateInitTimer.Inc(time.Since(substart).Milliseconds())
 
 	// Enable prefetching to pull in trie node paths while processing transactions
-	statedb.StartPrefetcher("chain", bc.cacheConfig.TriePrefetcherParallelism)
-	activeState = statedb
+	statedb.StartPrefetcher("chain", state.WithConcurrentWorkers(bc.cacheConfig.TriePrefetcherParallelism))
+	defer statedb.StopPrefetcher()
 
 	// Process block using the parent state as reference point
 	pstart := time.Now()
@@ -1736,10 +1726,8 @@ func (bc *BlockChain) reprocessBlock(parent *types.Block, current *types.Block)
 	}
 
 	// Enable prefetching to pull in trie node paths while processing transactions
-	statedb.StartPrefetcher("chain", bc.cacheConfig.TriePrefetcherParallelism)
-	defer func() {
-		statedb.StopPrefetcher()
-	}()
+	statedb.StartPrefetcher("chain", state.WithConcurrentWorkers(bc.cacheConfig.TriePrefetcherParallelism))
+	defer statedb.StopPrefetcher()
 
 	// Process previously stored block
 	receipts, _, usedGas, err := bc.processor.Process(current, parent.Header(), statedb, vm.Config{})

core/state/statedb.go

@@ -41,6 +41,7 @@ import (
 	"github.com/ava-labs/subnet-evm/trie"
 	"github.com/ava-labs/subnet-evm/trie/trienode"
 	"github.com/ava-labs/subnet-evm/trie/triestate"
+	"github.com/ava-labs/subnet-evm/utils"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/log"
@@ -200,16 +201,33 @@ func NewWithSnapshot(root common.Hash, db Database, snap snapshot.Snapshot) (*St
 	return sdb, nil
 }
 
+type workerPool struct {
+	*utils.BoundedWorkers
+}
+
+func (wp *workerPool) Done() {
+	// Done is guaranteed to only be called after all work is already complete,
+	// so Wait()ing is redundant, but it also releases resources.
+	wp.BoundedWorkers.Wait()
+}
+
+func WithConcurrentWorkers(prefetchers int) PrefetcherOption {
+	pool := &workerPool{
+		BoundedWorkers: utils.NewBoundedWorkers(prefetchers),
+	}
+	return WithWorkerPools(func() WorkerPool { return pool })
+}
+
 // StartPrefetcher initializes a new trie prefetcher to pull in nodes from the
 // state trie concurrently while the state is mutated so that when we reach the
 // commit phase, most of the needed data is already hot.
-func (s *StateDB) StartPrefetcher(namespace string, maxConcurrency int) {
+func (s *StateDB) StartPrefetcher(namespace string, opts ...PrefetcherOption) {
 	if s.prefetcher != nil {
 		s.prefetcher.close()
 		s.prefetcher = nil
 	}
 	if s.snap != nil {
-		s.prefetcher = newTriePrefetcher(s.db, s.originalRoot, namespace, maxConcurrency)
+		s.prefetcher = newTriePrefetcher(s.db, s.originalRoot, namespace, opts...)
 	}
 }