core/state: blocking prefetcher on term signal, parallel updates (#29519)

* core/state: trie prefetcher change: calling trie() doesn't stop the associated subfetcher

Co-authored-by: Martin HS <martin@swende.se>
Co-authored-by: Péter Szilágyi <peterke@gmail.com>

* core/state: improve prefetcher

* core/state: restore async prefetcher stask scheduling

* core/state: finish prefetching async and process storage updates async

* core/state: don't use the prefetcher for missing snapshot items

* core/state: remove update concurrency for Verkle tries

* core/state: add some termination checks to prefetcher async shutdowns

* core/state: differentiate db tries and prefetched tries

* core/state: teh teh teh

---------

Co-authored-by: Jared Wasinger <j-wasinger@hotmail.com>
Co-authored-by: Martin HS <martin@swende.se>
Co-authored-by: Gary Rong <garyrong0905@gmail.com>

core/blockchain.go

@@ -1805,8 +1805,12 @@ func (bc *BlockChain) insertChain(chain types.Blocks, setHead bool) (int, error)
 		}
 		statedb.SetLogger(bc.logger)
 
-		// Enable prefetching to pull in trie node paths while processing transactions
+		// If we are past Byzantium, enable prefetching to pull in trie node paths
+		// while processing transactions. Before Byzantium the prefetcher is mostly
+		// useless due to the intermediate root hashing after each transaction.
+		if bc.chainConfig.IsByzantium(block.Number()) {
 			statedb.StartPrefetcher("chain")
+		}
 		activeState = statedb
 
 		// If we have a followup block, run that against the current state to pre-cache

core/state/state_object.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"io"
 	"maps"
+	"sync"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -33,6 +34,14 @@ import (
 	"github.com/holiman/uint256"
 )
 
+// hasherPool holds a pool of hashers used by state objects during concurrent
+// trie updates.
+var hasherPool = sync.Pool{
+	New: func() interface{} {
+		return crypto.NewKeccakState()
+	},
+}
+
 type Storage map[common.Hash]common.Hash
 
 func (s Storage) Copy() Storage {
@@ -118,16 +127,12 @@ func (s *stateObject) touch() {
 	}
 }
 
-// getTrie returns the associated storage trie. The trie will be opened
+// getTrie returns the associated storage trie. The trie will be opened if it'
-// if it's not loaded previously. An error will be returned if trie can't
+// not loaded previously. An error will be returned if trie can't be loaded.
-// be loaded.
+//
+// If a new trie is opened, it will be cached within the state object to allow
+// subsequent reads to expand the same trie instead of reloading from disk.
 func (s *stateObject) getTrie() (Trie, error) {
-	if s.trie == nil {
-		// Try fetching from prefetcher first
-		if s.data.Root != types.EmptyRootHash && s.db.prefetcher != nil {
-			// When the miner is creating the pending state, there is no prefetcher
-			s.trie = s.db.prefetcher.trie(s.addrHash, s.data.Root)
-		}
 	if s.trie == nil {
 		tr, err := s.db.db.OpenStorageTrie(s.db.originalRoot, s.address, s.data.Root, s.db.trie)
 		if err != nil {
@@ -135,10 +140,26 @@ func (s *stateObject) getTrie() (Trie, error) {
 		}
 		s.trie = tr
 	}
-	}
 	return s.trie, nil
 }
 
+// getPrefetchedTrie returns the associated trie, as populated by the prefetcher
+// if it's available.
+//
+// Note, opposed to getTrie, this method will *NOT* blindly cache the resulting
+// trie in the state object. The caller might want to do that, but it's cleaner
+// to break the hidden interdependency between retrieving tries from the db or
+// from the prefetcher.
+func (s *stateObject) getPrefetchedTrie() (Trie, error) {
+	// If there's nothing to meaningfully return, let the user figure it out by
+	// pulling the trie from disk.
+	if s.data.Root == types.EmptyRootHash || s.db.prefetcher == nil {
+		return nil, nil
+	}
+	// Attempt to retrieve the trie from the pretecher
+	return s.db.prefetcher.trie(s.addrHash, s.data.Root)
+}
+
 // GetState retrieves a value from the account storage trie.
 func (s *stateObject) GetState(key common.Hash) common.Hash {
 	value, _ := s.getState(key)
@@ -248,7 +269,7 @@ func (s *stateObject) setState(key common.Hash, value common.Hash, origin common
 
 // finalise moves all dirty storage slots into the pending area to be hashed or
 // committed later. It is invoked at the end of every transaction.
-func (s *stateObject) finalise(prefetch bool) {
+func (s *stateObject) finalise() {
 	slotsToPrefetch := make([][]byte, 0, len(s.dirtyStorage))
 	for key, value := range s.dirtyStorage {
 		// If the slot is different from its original value, move it into the
@@ -263,8 +284,10 @@ func (s *stateObject) finalise(prefetch bool) {
 			delete(s.pendingStorage, key)
 		}
 	}
-	if s.db.prefetcher != nil && prefetch && len(slotsToPrefetch) > 0 && s.data.Root != types.EmptyRootHash {
+	if s.db.prefetcher != nil && len(slotsToPrefetch) > 0 && s.data.Root != types.EmptyRootHash {
-		s.db.prefetcher.prefetch(s.addrHash, s.data.Root, s.address, slotsToPrefetch)
+		if err := s.db.prefetcher.prefetch(s.addrHash, s.data.Root, s.address, slotsToPrefetch); err != nil {
+			log.Error("Failed to prefetch slots", "addr", s.address, "slots", len(slotsToPrefetch), "err", err)
+		}
 	}
 	if len(s.dirtyStorage) > 0 {
 		s.dirtyStorage = make(Storage)
@@ -283,25 +306,43 @@ func (s *stateObject) finalise(prefetch bool) {
 // storage change at all.
 func (s *stateObject) updateTrie() (Trie, error) {
 	// Make sure all dirty slots are finalized into the pending storage area
-	s.finalise(false)
+	s.finalise()
 
 	// Short circuit if nothing changed, don't bother with hashing anything
 	if len(s.pendingStorage) == 0 {
 		return s.trie, nil
 	}
+	// Retrieve a pretecher populated trie, or fall back to the database
+	tr, err := s.getPrefetchedTrie()
+	switch {
+	case err != nil:
+		// Fetcher retrieval failed, something's very wrong, abort
+		s.db.setError(err)
+		return nil, err
+
+	case tr == nil:
+		// Fetcher not running or empty trie, fallback to the database trie
+		tr, err = s.getTrie()
+		if err != nil {
+			s.db.setError(err)
+			return nil, err
+		}
+
+	default:
+		// Prefetcher returned a live trie, swap it out for the current one
+		s.trie = tr
+	}
 	// The snapshot storage map for the object
 	var (
 		storage map[common.Hash][]byte
 		origin  map[common.Hash][]byte
 	)
-	tr, err := s.getTrie()
-	if err != nil {
-		s.db.setError(err)
-		return nil, err
-	}
 	// Insert all the pending storage updates into the trie
 	usedStorage := make([][]byte, 0, len(s.pendingStorage))
 
+	hasher := hasherPool.Get().(crypto.KeccakState)
+	defer hasherPool.Put(hasher)
+
 	// Perform trie updates before deletions.  This prevents resolution of unnecessary trie nodes
 	//  in circumstances similar to the following:
 	//
@@ -330,26 +371,30 @@ func (s *stateObject) updateTrie() (Trie, error) {
 				s.db.setError(err)
 				return nil, err
 			}
-			s.db.StorageUpdated += 1
+			s.db.StorageUpdated.Add(1)
 		} else {
 			deletions = append(deletions, key)
 		}
 		// Cache the mutated storage slots until commit
 		if storage == nil {
+			s.db.storagesLock.Lock()
 			if storage = s.db.storages[s.addrHash]; storage == nil {
 				storage = make(map[common.Hash][]byte)
 				s.db.storages[s.addrHash] = storage
 			}
+			s.db.storagesLock.Unlock()
 		}
-		khash := crypto.HashData(s.db.hasher, key[:])
+		khash := crypto.HashData(hasher, key[:])
 		storage[khash] = encoded // encoded will be nil if it's deleted
 
 		// Cache the original value of mutated storage slots
 		if origin == nil {
+			s.db.storagesLock.Lock()
 			if origin = s.db.storagesOrigin[s.address]; origin == nil {
 				origin = make(map[common.Hash][]byte)
 				s.db.storagesOrigin[s.address] = origin
 			}
+			s.db.storagesLock.Unlock()
 		}
 		// Track the original value of slot only if it's mutated first time
 		if _, ok := origin[khash]; !ok {
@@ -369,7 +414,7 @@ func (s *stateObject) updateTrie() (Trie, error) {
 			s.db.setError(err)
 			return nil, err
 		}
-		s.db.StorageDeleted += 1
+		s.db.StorageDeleted.Add(1)
 	}
 	// If no slots were touched, issue a warning as we shouldn't have done all
 	// the above work in the first place

core/state/statedb.go

@@ -24,6 +24,7 @@ import (
 	"slices"
 	"sort"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -97,9 +98,11 @@ type StateDB struct {
 	// These maps hold the state changes (including the corresponding
 	// original value) that occurred in this **block**.
 	accounts       map[common.Hash][]byte    // The mutated accounts in 'slim RLP' encoding
-	storages       map[common.Hash]map[common.Hash][]byte    // The mutated slots in prefix-zero trimmed rlp format
 	accountsOrigin map[common.Address][]byte // The original value of mutated accounts in 'slim RLP' encoding
+
+	storages       map[common.Hash]map[common.Hash][]byte    // The mutated slots in prefix-zero trimmed rlp format
 	storagesOrigin map[common.Address]map[common.Hash][]byte // The original value of mutated slots in prefix-zero trimmed rlp format
+	storagesLock   sync.Mutex                                // Mutex protecting the maps during concurrent updates/commits
 
 	// This map holds 'live' objects, which will get modified while
 	// processing a state transition.
@@ -165,9 +168,9 @@ type StateDB struct {
 	TrieDBCommits        time.Duration
 
 	AccountUpdated int
-	StorageUpdated int
+	StorageUpdated atomic.Int64
 	AccountDeleted int
-	StorageDeleted int
+	StorageDeleted atomic.Int64
 
 	// Testing hooks
 	onCommit func(states *triestate.Set) // Hook invoked when commit is performed
@@ -214,7 +217,8 @@ func (s *StateDB) SetLogger(l *tracing.Hooks) {
 // commit phase, most of the needed data is already hot.
 func (s *StateDB) StartPrefetcher(namespace string) {
 	if s.prefetcher != nil {
-		s.prefetcher.close()
+		s.prefetcher.terminate(false)
+		s.prefetcher.report()
 		s.prefetcher = nil
 	}
 	if s.snap != nil {
@@ -226,7 +230,8 @@ func (s *StateDB) StartPrefetcher(namespace string) {
 // from the gathered metrics.
 func (s *StateDB) StopPrefetcher() {
 	if s.prefetcher != nil {
-		s.prefetcher.close()
+		s.prefetcher.terminate(false)
+		s.prefetcher.report()
 		s.prefetcher = nil
 	}
 }
@@ -544,9 +549,6 @@ func (s *StateDB) GetTransientState(addr common.Address, key common.Hash) common
 
 // updateStateObject writes the given object to the trie.
 func (s *StateDB) updateStateObject(obj *stateObject) {
-	// Track the amount of time wasted on updating the account from the trie
-	defer func(start time.Time) { s.AccountUpdates += time.Since(start) }(time.Now())
-
 	// Encode the account and update the account trie
 	addr := obj.Address()
 	if err := s.trie.UpdateAccount(addr, &obj.data); err != nil {
@@ -575,10 +577,6 @@ func (s *StateDB) updateStateObject(obj *stateObject) {
 
 // deleteStateObject removes the given object from the state trie.
 func (s *StateDB) deleteStateObject(addr common.Address) {
-	// Track the amount of time wasted on deleting the account from the trie
-	defer func(start time.Time) { s.AccountUpdates += time.Since(start) }(time.Now())
-
-	// Delete the account from the trie
 	if err := s.trie.DeleteAccount(addr); err != nil {
 		s.setError(fmt.Errorf("deleteStateObject (%x) error: %v", addr[:], err))
 	}
@@ -743,13 +741,6 @@ func (s *StateDB) Copy() *StateDB {
 	// in the middle of a transaction.
 	state.accessList = s.accessList.Copy()
 	state.transientStorage = s.transientStorage.Copy()
-
-	// If there's a prefetcher running, make an inactive copy of it that can
-	// only access data but does not actively preload (since the user will not
-	// know that they need to explicitly terminate an active copy).
-	if s.prefetcher != nil {
-		state.prefetcher = s.prefetcher.copy()
-	}
 	return state
 }
 
@@ -820,7 +811,7 @@ func (s *StateDB) Finalise(deleteEmptyObjects bool) {
 			delete(s.accountsOrigin, obj.address) // Clear out any previously updated account data (may be recreated via a resurrect)
 			delete(s.storagesOrigin, obj.address) // Clear out any previously updated storage data (may be recreated via a resurrect)
 		} else {
-			obj.finalise(true) // Prefetch slots in the background
+			obj.finalise()
 			s.markUpdate(addr)
 		}
 		// At this point, also ship the address off to the precacher. The precacher
@@ -829,7 +820,9 @@ func (s *StateDB) Finalise(deleteEmptyObjects bool) {
 		addressesToPrefetch = append(addressesToPrefetch, common.CopyBytes(addr[:])) // Copy needed for closure
 	}
 	if s.prefetcher != nil && len(addressesToPrefetch) > 0 {
-		s.prefetcher.prefetch(common.Hash{}, s.originalRoot, common.Address{}, addressesToPrefetch)
+		if err := s.prefetcher.prefetch(common.Hash{}, s.originalRoot, common.Address{}, addressesToPrefetch); err != nil {
+			log.Error("Failed to prefetch addresses", "addresses", len(addressesToPrefetch), "err", err)
+		}
 	}
 	// Invalidate journal because reverting across transactions is not allowed.
 	s.clearJournalAndRefund()
@@ -842,42 +835,52 @@ func (s *StateDB) IntermediateRoot(deleteEmptyObjects bool) common.Hash {
 	// Finalise all the dirty storage states and write them into the tries
 	s.Finalise(deleteEmptyObjects)
 
-	// If there was a trie prefetcher operating, it gets aborted and irrevocably
+	// If there was a trie prefetcher operating, terminate it async so that the
-	// modified after we start retrieving tries. Remove it from the statedb after
+	// individual storage tries can be updated as soon as the disk load finishes.
-	// this round of use.
-	//
-	// This is weird pre-byzantium since the first tx runs with a prefetcher and
-	// the remainder without, but pre-byzantium even the initial prefetcher is
-	// useless, so no sleep lost.
-	prefetcher := s.prefetcher
 	if s.prefetcher != nil {
+		s.prefetcher.terminate(true)
 		defer func() {
-			s.prefetcher.close()
+			s.prefetcher.report()
-			s.prefetcher = nil
+			s.prefetcher = nil // Pre-byzantium, unset any used up prefetcher
 		}()
 	}
-	// Although naively it makes sense to retrieve the account trie and then do
+	// Process all storage updates concurrently. The state object update root
-	// the contract storage and account updates sequentially, that short circuits
+	// method will internally call a blocking trie fetch from the prefetcher,
-	// the account prefetcher. Instead, let's process all the storage updates
+	// so there's no need to explicitly wait for the prefetchers to finish.
-	// first, giving the account prefetches just a few more milliseconds of time
+	var (
-	// to pull useful data from disk.
+		start   = time.Now()
-	start := time.Now()
+		workers errgroup.Group
+	)
+	if s.db.TrieDB().IsVerkle() {
+		// Whilst MPT storage tries are independent, Verkle has one single trie
+		// for all the accounts and all the storage slots merged together. The
+		// former can thus be simply parallelized, but updating the latter will
+		// need concurrency support within the trie itself. That's a TODO for a
+		// later time.
+		workers.SetLimit(1)
+	}
 	for addr, op := range s.mutations {
-		if op.applied {
+		if op.applied || op.isDelete() {
 			continue
 		}
-		if op.isDelete() {
+		obj := s.stateObjects[addr] // closure for the task runner below
-			continue
+		workers.Go(func() error {
-		}
+			obj.updateRoot()
-		s.stateObjects[addr].updateRoot()
+			return nil
+		})
 	}
+	workers.Wait()
 	s.StorageUpdates += time.Since(start)
 
 	// Now we're about to start to write changes to the trie. The trie is so far
 	// _untouched_. We can check with the prefetcher, if it can give us a trie
 	// which has the same root, but also has some content loaded into it.
-	if prefetcher != nil {
+	start = time.Now()
-		if trie := prefetcher.trie(common.Hash{}, s.originalRoot); trie != nil {
+
+	if s.prefetcher != nil {
+		if trie, err := s.prefetcher.trie(common.Hash{}, s.originalRoot); err != nil {
+			log.Error("Failed to retrieve account pre-fetcher trie", "err", err)
+		} else if trie != nil {
 			s.trie = trie
 		}
 	}
@@ -913,8 +916,10 @@ func (s *StateDB) IntermediateRoot(deleteEmptyObjects bool) common.Hash {
 		s.deleteStateObject(deletedAddr)
 		s.AccountDeleted += 1
 	}
-	if prefetcher != nil {
+	s.AccountUpdates += time.Since(start)
-		prefetcher.used(common.Hash{}, s.originalRoot, usedAddrs)
+
+	if s.prefetcher != nil {
+		s.prefetcher.used(common.Hash{}, s.originalRoot, usedAddrs)
 	}
 	// Track the amount of time wasted on hashing the account trie
 	defer func(start time.Time) { s.AccountHashes += time.Since(start) }(time.Now())
@@ -1255,15 +1260,16 @@ func (s *StateDB) Commit(block uint64, deleteEmptyObjects bool) (common.Hash, er
 		return common.Hash{}, err
 	}
 	accountUpdatedMeter.Mark(int64(s.AccountUpdated))
-	storageUpdatedMeter.Mark(int64(s.StorageUpdated))
+	storageUpdatedMeter.Mark(s.StorageUpdated.Load())
 	accountDeletedMeter.Mark(int64(s.AccountDeleted))
-	storageDeletedMeter.Mark(int64(s.StorageDeleted))
+	storageDeletedMeter.Mark(s.StorageDeleted.Load())
 	accountTrieUpdatedMeter.Mark(int64(accountTrieNodesUpdated))
 	accountTrieDeletedMeter.Mark(int64(accountTrieNodesDeleted))
 	storageTriesUpdatedMeter.Mark(int64(storageTrieNodesUpdated))
 	storageTriesDeletedMeter.Mark(int64(storageTrieNodesDeleted))
 	s.AccountUpdated, s.AccountDeleted = 0, 0
-	s.StorageUpdated, s.StorageDeleted = 0, 0
+	s.StorageUpdated.Store(0)
+	s.StorageDeleted.Store(0)
 
 	// If snapshotting is enabled, update the snapshot tree with this new version
 	if s.snap != nil {

core/state/trie_prefetcher.go

@@ -17,6 +17,7 @@
 package state
 
 import (
+	"errors"
 	"sync"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -27,6 +28,10 @@ import (
 var (
 	// triePrefetchMetricsPrefix is the prefix under which to publish the metrics.
 	triePrefetchMetricsPrefix = "trie/prefetch/"
+
+	// errTerminated is returned if a fetcher is attempted to be operated after it
+	// has already terminated.
+	errTerminated = errors.New("fetcher is already terminated")
 )
 
 // triePrefetcher is an active prefetcher, which receives accounts or storage
@@ -37,52 +42,64 @@ var (
 type triePrefetcher struct {
 	db       Database               // Database to fetch trie nodes through
 	root     common.Hash            // Root hash of the account trie for metrics
-	fetches  map[string]Trie        // Partially or fully fetched tries. Only populated for inactive copies.
 	fetchers map[string]*subfetcher // Subfetchers for each trie
+	term     chan struct{}          // Channel to signal interruption
 
 	deliveryMissMeter metrics.Meter
 	accountLoadMeter  metrics.Meter
 	accountDupMeter   metrics.Meter
-	accountSkipMeter  metrics.Meter
 	accountWasteMeter metrics.Meter
 	storageLoadMeter  metrics.Meter
 	storageDupMeter   metrics.Meter
-	storageSkipMeter  metrics.Meter
 	storageWasteMeter metrics.Meter
 }
 
 func newTriePrefetcher(db Database, root common.Hash, namespace string) *triePrefetcher {
 	prefix := triePrefetchMetricsPrefix + namespace
-	p := &triePrefetcher{
+	return &triePrefetcher{
 		db:       db,
 		root:     root,
 		fetchers: make(map[string]*subfetcher), // Active prefetchers use the fetchers map
+		term:     make(chan struct{}),
 
 		deliveryMissMeter: metrics.GetOrRegisterMeter(prefix+"/deliverymiss", nil),
 		accountLoadMeter:  metrics.GetOrRegisterMeter(prefix+"/account/load", nil),
 		accountDupMeter:   metrics.GetOrRegisterMeter(prefix+"/account/dup", nil),
-		accountSkipMeter:  metrics.GetOrRegisterMeter(prefix+"/account/skip", nil),
 		accountWasteMeter: metrics.GetOrRegisterMeter(prefix+"/account/waste", nil),
 		storageLoadMeter:  metrics.GetOrRegisterMeter(prefix+"/storage/load", nil),
 		storageDupMeter:   metrics.GetOrRegisterMeter(prefix+"/storage/dup", nil),
-		storageSkipMeter:  metrics.GetOrRegisterMeter(prefix+"/storage/skip", nil),
 		storageWasteMeter: metrics.GetOrRegisterMeter(prefix+"/storage/waste", nil),
 	}
-	return p
 }
 
-// close iterates over all the subfetchers, aborts any that were left spinning
+// terminate iterates over all the subfetchers and issues a terminateion request
-// and reports the stats to the metrics subsystem.
+// to all of them. Depending on the async parameter, the method will either block
-func (p *triePrefetcher) close() {
+// until all subfetchers spin down, or return immediately.
+func (p *triePrefetcher) terminate(async bool) {
+	// Short circuit if the fetcher is already closed
+	select {
+	case <-p.term:
+		return
+	default:
+	}
+	// Termiante all sub-fetchers, sync or async, depending on the request
 	for _, fetcher := range p.fetchers {
-		fetcher.abort() // safe to do multiple times
+		fetcher.terminate(async)
+	}
+	close(p.term)
+}
+
+// report aggregates the pre-fetching and usage metrics and reports them.
+func (p *triePrefetcher) report() {
+	if !metrics.Enabled {
+		return
+	}
+	for _, fetcher := range p.fetchers {
+		fetcher.wait() // ensure the fetcher's idle before poking in its internals
 
-		if metrics.Enabled {
 		if fetcher.root == p.root {
 			p.accountLoadMeter.Mark(int64(len(fetcher.seen)))
 			p.accountDupMeter.Mark(int64(fetcher.dups))
-				p.accountSkipMeter.Mark(int64(len(fetcher.tasks)))
-
 			for _, key := range fetcher.used {
 				delete(fetcher.seen, string(key))
 			}
@@ -90,8 +107,6 @@ func (p *triePrefetcher) close() {
 		} else {
 			p.storageLoadMeter.Mark(int64(len(fetcher.seen)))
 			p.storageDupMeter.Mark(int64(fetcher.dups))
-				p.storageSkipMeter.Mark(int64(len(fetcher.tasks)))
-
 			for _, key := range fetcher.used {
 				delete(fetcher.seen, string(key))
 			}
@@ -99,98 +114,54 @@ func (p *triePrefetcher) close() {
 		}
 	}
 }
-	// Clear out all fetchers (will crash on a second call, deliberate)
-	p.fetchers = nil
-}
 
-// copy creates a deep-but-inactive copy of the trie prefetcher. Any trie data
+// prefetch schedules a batch of trie items to prefetch. After the prefetcher is
-// already loaded will be copied over, but no goroutines will be started. This
+// closed, all the following tasks scheduled will not be executed and an error
-// is mostly used in the miner which creates a copy of it's actively mutated
+// will be returned.
-// state to be sealed while it may further mutate the state.
+//
-func (p *triePrefetcher) copy() *triePrefetcher {
+// prefetch is called from two locations:
-	copy := &triePrefetcher{
+//
-		db:      p.db,
+//  1. Finalize of the state-objects storage roots. This happens at the end
-		root:    p.root,
+//     of every transaction, meaning that if several transactions touches
-		fetches: make(map[string]Trie), // Active prefetchers use the fetches map
+//     upon the same contract, the parameters invoking this method may be
-
+//     repeated.
-		deliveryMissMeter: p.deliveryMissMeter,
+//  2. Finalize of the main account trie. This happens only once per block.
-		accountLoadMeter:  p.accountLoadMeter,
+func (p *triePrefetcher) prefetch(owner common.Hash, root common.Hash, addr common.Address, keys [][]byte) error {
-		accountDupMeter:   p.accountDupMeter,
+	// Ensure the subfetcher is still alive
-		accountSkipMeter:  p.accountSkipMeter,
+	select {
-		accountWasteMeter: p.accountWasteMeter,
+	case <-p.term:
-		storageLoadMeter:  p.storageLoadMeter,
+		return errTerminated
-		storageDupMeter:   p.storageDupMeter,
+	default:
-		storageSkipMeter:  p.storageSkipMeter,
-		storageWasteMeter: p.storageWasteMeter,
 	}
-	// If the prefetcher is already a copy, duplicate the data
-	if p.fetches != nil {
-		for root, fetch := range p.fetches {
-			if fetch == nil {
-				continue
-			}
-			copy.fetches[root] = p.db.CopyTrie(fetch)
-		}
-		return copy
-	}
-	// Otherwise we're copying an active fetcher, retrieve the current states
-	for id, fetcher := range p.fetchers {
-		copy.fetches[id] = fetcher.peek()
-	}
-	return copy
-}
-
-// prefetch schedules a batch of trie items to prefetch.
-func (p *triePrefetcher) prefetch(owner common.Hash, root common.Hash, addr common.Address, keys [][]byte) {
-	// If the prefetcher is an inactive one, bail out
-	if p.fetches != nil {
-		return
-	}
-	// Active fetcher, schedule the retrievals
 	id := p.trieID(owner, root)
 	fetcher := p.fetchers[id]
 	if fetcher == nil {
 		fetcher = newSubfetcher(p.db, p.root, owner, root, addr)
 		p.fetchers[id] = fetcher
 	}
-	fetcher.schedule(keys)
+	return fetcher.schedule(keys)
 }
 
-// trie returns the trie matching the root hash, or nil if the prefetcher doesn't
+// trie returns the trie matching the root hash, blocking until the fetcher of
-// have it.
+// the given trie terminates. If no fetcher exists for the request, nil will be
-func (p *triePrefetcher) trie(owner common.Hash, root common.Hash) Trie {
+// returned.
-	// If the prefetcher is inactive, return from existing deep copies
+func (p *triePrefetcher) trie(owner common.Hash, root common.Hash) (Trie, error) {
-	id := p.trieID(owner, root)
+	// Bail if no trie was prefetched for this root
-	if p.fetches != nil {
+	fetcher := p.fetchers[p.trieID(owner, root)]
-		trie := p.fetches[id]
-		if trie == nil {
-			p.deliveryMissMeter.Mark(1)
-			return nil
-		}
-		return p.db.CopyTrie(trie)
-	}
-	// Otherwise the prefetcher is active, bail if no trie was prefetched for this root
-	fetcher := p.fetchers[id]
 	if fetcher == nil {
+		log.Error("Prefetcher missed to load trie", "owner", owner, "root", root)
 		p.deliveryMissMeter.Mark(1)
-		return nil
+		return nil, nil
 	}
-	// Interrupt the prefetcher if it's by any chance still running and return
+	// Subfetcher exists, retrieve its trie
-	// a copy of any pre-loaded trie.
+	return fetcher.peek(), nil
-	fetcher.abort() // safe to do multiple times
-
-	trie := fetcher.peek()
-	if trie == nil {
-		p.deliveryMissMeter.Mark(1)
-		return nil
-	}
-	return trie
 }
 
 // used marks a batch of state items used to allow creating statistics as to
-// how useful or wasteful the prefetcher is.
+// how useful or wasteful the fetcher is.
 func (p *triePrefetcher) used(owner common.Hash, root common.Hash, used [][]byte) {
 	if fetcher := p.fetchers[p.trieID(owner, root)]; fetcher != nil {
+		fetcher.wait() // ensure the fetcher's idle before poking in its internals
 		fetcher.used = used
 	}
 }
@@ -221,7 +192,6 @@ type subfetcher struct {
 	wake chan struct{} // Wake channel if a new task is scheduled
 	stop chan struct{} // Channel to interrupt processing
 	term chan struct{} // Channel to signal interruption
-	copy chan chan Trie // Channel to request a copy of the current trie
 
 	seen map[string]struct{} // Tracks the entries already loaded
 	dups int                 // Number of duplicate preload tasks
@@ -240,7 +210,6 @@ func newSubfetcher(db Database, state common.Hash, owner common.Hash, root commo
 		wake:  make(chan struct{}, 1),
 		stop:  make(chan struct{}),
 		term:  make(chan struct{}),
-		copy:  make(chan chan Trie),
 		seen:  make(map[string]struct{}),
 	}
 	go sf.loop()
@@ -248,50 +217,61 @@ func newSubfetcher(db Database, state common.Hash, owner common.Hash, root commo
 }
 
 // schedule adds a batch of trie keys to the queue to prefetch.
-func (sf *subfetcher) schedule(keys [][]byte) {
+func (sf *subfetcher) schedule(keys [][]byte) error {
+	// Ensure the subfetcher is still alive
+	select {
+	case <-sf.term:
+		return errTerminated
+	default:
+	}
 	// Append the tasks to the current queue
 	sf.lock.Lock()
 	sf.tasks = append(sf.tasks, keys...)
 	sf.lock.Unlock()
 
-	// Notify the prefetcher, it's fine if it's already terminated
+	// Notify the background thread to execute scheduled tasks
 	select {
 	case sf.wake <- struct{}{}:
+		// Wake signal sent
 	default:
+		// Wake signal not sent as a previous is already queued
 	}
-}
-
-// peek tries to retrieve a deep copy of the fetcher's trie in whatever form it
-// is currently.
-func (sf *subfetcher) peek() Trie {
-	ch := make(chan Trie)
-	select {
-	case sf.copy <- ch:
-		// Subfetcher still alive, return copy from it
-		return <-ch
-
-	case <-sf.term:
-		// Subfetcher already terminated, return a copy directly
-		if sf.trie == nil {
 	return nil
 }
-		return sf.db.CopyTrie(sf.trie)
+
-	}
+// wait blocks until the subfetcher terminates. This method is used to block on
+// an async termination before accessing internal fields from the fetcher.
+func (sf *subfetcher) wait() {
+	<-sf.term
 }
 
-// abort interrupts the subfetcher immediately. It is safe to call abort multiple
+// peek retrieves the fetcher's trie, populated with any pre-fetched data. The
-// times but it is not thread safe.
+// returned trie will be a shallow copy, so modifying it will break subsequent
-func (sf *subfetcher) abort() {
+// peeks for the original data. The method will block until all the scheduled
+// data has been loaded and the fethcer terminated.
+func (sf *subfetcher) peek() Trie {
+	// Block until the fertcher terminates, then retrieve the trie
+	sf.wait()
+	return sf.trie
+}
+
+// terminate requests the subfetcher to stop accepting new tasks and spin down
+// as soon as everything is loaded. Depending on the async parameter, the method
+// will either block until all disk loads finish or return immediately.
+func (sf *subfetcher) terminate(async bool) {
 	select {
 	case <-sf.stop:
 	default:
 		close(sf.stop)
 	}
+	if async {
+		return
+	}
 	<-sf.term
 }
 
-// loop waits for new tasks to be scheduled and keeps loading them until it runs
+// loop loads newly-scheduled trie tasks as they are received and loads them, stopping
-// out of tasks or its underlying trie is retrieved for committing.
+// when requested.
 func (sf *subfetcher) loop() {
 	// No matter how the loop stops, signal anyone waiting that it's terminated
 	defer close(sf.term)
@@ -305,8 +285,6 @@ func (sf *subfetcher) loop() {
 		}
 		sf.trie = trie
 	} else {
-		// The trie argument can be nil as verkle doesn't support prefetching
-		// yet. TODO FIX IT(rjl493456442), otherwise code will panic here.
 		trie, err := sf.db.OpenStorageTrie(sf.state, sf.addr, sf.root, nil)
 		if err != nil {
 			log.Warn("Trie prefetcher failed opening trie", "root", sf.root, "err", err)
@@ -318,31 +296,17 @@ func (sf *subfetcher) loop() {
 	for {
 		select {
 		case <-sf.wake:
-			// Subfetcher was woken up, retrieve any tasks to avoid spinning the lock
+			// Execute all remaining tasks in single run
 			sf.lock.Lock()
 			tasks := sf.tasks
 			sf.tasks = nil
 			sf.lock.Unlock()
 
-			// Prefetch any tasks until the loop is interrupted
+			for _, task := range tasks {
-			for i, task := range tasks {
-				select {
-				case <-sf.stop:
-					// If termination is requested, add any leftover back and return
-					sf.lock.Lock()
-					sf.tasks = append(sf.tasks, tasks[i:]...)
-					sf.lock.Unlock()
-					return
-
-				case ch := <-sf.copy:
-					// Somebody wants a copy of the current trie, grant them
-					ch <- sf.db.CopyTrie(sf.trie)
-
-				default:
-					// No termination request yet, prefetch the next entry
 				if _, ok := sf.seen[string(task)]; ok {
 					sf.dups++
-					} else {
+					continue
+				}
 				if len(task) == common.AddressLength {
 					sf.trie.GetAccount(common.BytesToAddress(task))
 				} else {
@@ -350,16 +314,20 @@ func (sf *subfetcher) loop() {
 				}
 				sf.seen[string(task)] = struct{}{}
 			}
-				}
-			}
-
-		case ch := <-sf.copy:
-			// Somebody wants a copy of the current trie, grant them
-			ch <- sf.db.CopyTrie(sf.trie)
 
 		case <-sf.stop:
-			// Termination is requested, abort and leave remaining tasks
+			// Termination is requested, abort if no more tasks are pending. If
+			// there are some, exhaust them first.
+			sf.lock.Lock()
+			done := sf.tasks == nil
+			sf.lock.Unlock()
+
+			if done {
 				return
 			}
+			// Some tasks are pending, loop and pick them up (that wake branch
+			// will be selected eventually, whilst stop remains closed to this
+			// branch will also run afterwards).
+		}
 	}
 }

core/state/trie_prefetcher_test.go

@@ -19,7 +19,6 @@ package state
 import (
 	"math/big"
 	"testing"
-	"time"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/rawdb"
@@ -46,68 +45,20 @@ func filledStateDB() *StateDB {
 	return state
 }
 
-func TestCopyAndClose(t *testing.T) {
+func TestUseAfterTerminate(t *testing.T) {
 	db := filledStateDB()
 	prefetcher := newTriePrefetcher(db.db, db.originalRoot, "")
 	skey := common.HexToHash("aaa")
-	prefetcher.prefetch(common.Hash{}, db.originalRoot, common.Address{}, [][]byte{skey.Bytes()})
-	prefetcher.prefetch(common.Hash{}, db.originalRoot, common.Address{}, [][]byte{skey.Bytes()})
-	time.Sleep(1 * time.Second)
-	a := prefetcher.trie(common.Hash{}, db.originalRoot)
-	prefetcher.prefetch(common.Hash{}, db.originalRoot, common.Address{}, [][]byte{skey.Bytes()})
-	b := prefetcher.trie(common.Hash{}, db.originalRoot)
-	cpy := prefetcher.copy()
-	cpy.prefetch(common.Hash{}, db.originalRoot, common.Address{}, [][]byte{skey.Bytes()})
-	cpy.prefetch(common.Hash{}, db.originalRoot, common.Address{}, [][]byte{skey.Bytes()})
-	c := cpy.trie(common.Hash{}, db.originalRoot)
-	prefetcher.close()
-	cpy2 := cpy.copy()
-	cpy2.prefetch(common.Hash{}, db.originalRoot, common.Address{}, [][]byte{skey.Bytes()})
-	d := cpy2.trie(common.Hash{}, db.originalRoot)
-	cpy.close()
-	cpy2.close()
-	if a.Hash() != b.Hash() || a.Hash() != c.Hash() || a.Hash() != d.Hash() {
-		t.Fatalf("Invalid trie, hashes should be equal: %v %v %v %v", a.Hash(), b.Hash(), c.Hash(), d.Hash())
-	}
-}
 
-func TestUseAfterClose(t *testing.T) {
+	if err := prefetcher.prefetch(common.Hash{}, db.originalRoot, common.Address{}, [][]byte{skey.Bytes()}); err != nil {
-	db := filledStateDB()
+		t.Errorf("Prefetch failed before terminate: %v", err)
-	prefetcher := newTriePrefetcher(db.db, db.originalRoot, "")
-	skey := common.HexToHash("aaa")
-	prefetcher.prefetch(common.Hash{}, db.originalRoot, common.Address{}, [][]byte{skey.Bytes()})
-	a := prefetcher.trie(common.Hash{}, db.originalRoot)
-	prefetcher.close()
-	b := prefetcher.trie(common.Hash{}, db.originalRoot)
-	if a == nil {
-		t.Fatal("Prefetching before close should not return nil")
-	}
-	if b != nil {
-		t.Fatal("Trie after close should return nil")
-	}
 	}
+	prefetcher.terminate(false)
 
-func TestCopyClose(t *testing.T) {
+	if err := prefetcher.prefetch(common.Hash{}, db.originalRoot, common.Address{}, [][]byte{skey.Bytes()}); err == nil {
-	db := filledStateDB()
+		t.Errorf("Prefetch succeeded after terminate: %v", err)
-	prefetcher := newTriePrefetcher(db.db, db.originalRoot, "")
-	skey := common.HexToHash("aaa")
-	prefetcher.prefetch(common.Hash{}, db.originalRoot, common.Address{}, [][]byte{skey.Bytes()})
-	cpy := prefetcher.copy()
-	a := prefetcher.trie(common.Hash{}, db.originalRoot)
-	b := cpy.trie(common.Hash{}, db.originalRoot)
-	prefetcher.close()
-	c := prefetcher.trie(common.Hash{}, db.originalRoot)
-	d := cpy.trie(common.Hash{}, db.originalRoot)
-	if a == nil {
-		t.Fatal("Prefetching before close should not return nil")
 	}
-	if b == nil {
+	if _, err := prefetcher.trie(common.Hash{}, db.originalRoot); err != nil {
-		t.Fatal("Copy trie should return nil")
+		t.Errorf("Trie retrieval failed after terminate: %v", err)
-	}
-	if c != nil {
-		t.Fatal("Trie after close should return nil")
-	}
-	if d == nil {
-		t.Fatal("Copy trie should not return nil")
 	}
 }