Merge pull request #21047 from holiman/improve_updates_2

core: improve trie updates (part 2)

accounts/abi/bind/backends/simulated.go

@@ -125,10 +125,9 @@ func (b *SimulatedBackend) Rollback() {
 
 func (b *SimulatedBackend) rollback() {
 	blocks, _ := core.GenerateChain(b.config, b.blockchain.CurrentBlock(), ethash.NewFaker(), b.database, 1, func(int, *core.BlockGen) {})
-	stateDB, _ := b.blockchain.State()
 
 	b.pendingBlock = blocks[0]
-	b.pendingState, _ = state.New(b.pendingBlock.Root(), stateDB.Database(), nil)
+	b.pendingState, _ = state.New(b.pendingBlock.Root(), b.blockchain.StateCache(), nil)
 }
 
 // stateByBlockNumber retrieves a state by a given blocknumber.

core/blockchain.go

@@ -203,7 +203,7 @@ type BlockChain struct {
 
 	engine     consensus.Engine
 	validator  Validator // Block and state validator interface
-	prefetcher Prefetcher // Block state prefetcher interface
+	prefetcher Prefetcher
 	processor  Processor // Block transaction processor interface
 	vmConfig   vm.Config
 
@@ -1860,12 +1860,17 @@ func (bc *BlockChain) insertChain(chain types.Blocks, verifySeals bool) (int, er
 		if err != nil {
 			return it.index, err
 		}
+		// Enable prefetching to pull in trie node paths while processing transactions
+		statedb.StartPrefetcher("chain")
+		defer statedb.StopPrefetcher() // stopped on write anyway, defer meant to catch early error returns
+
 		// If we have a followup block, run that against the current state to pre-cache
 		// transactions and probabilistically some of the account/storage trie nodes.
 		var followupInterrupt uint32
 		if !bc.cacheConfig.TrieCleanNoPrefetch {
 			if followup, err := it.peek(); followup != nil && err == nil {
 				throwaway, _ := state.New(parent.Root, bc.stateCache, bc.snaps)
+
 				go func(start time.Time, followup *types.Block, throwaway *state.StateDB, interrupt *uint32) {
 					bc.prefetcher.Prefetch(followup, throwaway, bc.vmConfig, &followupInterrupt)
 
@@ -1891,7 +1896,6 @@ func (bc *BlockChain) insertChain(chain types.Blocks, verifySeals bool) (int, er
 		storageUpdateTimer.Update(statedb.StorageUpdates)             // Storage updates are complete, we can mark them
 		snapshotAccountReadTimer.Update(statedb.SnapshotAccountReads) // Account reads are complete, we can mark them
 		snapshotStorageReadTimer.Update(statedb.SnapshotStorageReads) // Storage reads are complete, we can mark them
-
 		triehash := statedb.AccountHashes + statedb.StorageHashes     // Save to not double count in validation
 		trieproc := statedb.SnapshotAccountReads + statedb.AccountReads + statedb.AccountUpdates
 		trieproc += statedb.SnapshotStorageReads + statedb.StorageReads + statedb.StorageUpdates
@@ -1920,7 +1924,6 @@ func (bc *BlockChain) insertChain(chain types.Blocks, verifySeals bool) (int, er
 		if err != nil {
 			return it.index, err
 		}
-
 		// Update the metrics touched during block commit
 		accountCommitTimer.Update(statedb.AccountCommits)   // Account commits are complete, we can mark them
 		storageCommitTimer.Update(statedb.StorageCommits)   // Storage commits are complete, we can mark them

core/state/database.go

@@ -129,12 +129,20 @@ type cachingDB struct {
 
 // OpenTrie opens the main account trie at a specific root hash.
 func (db *cachingDB) OpenTrie(root common.Hash) (Trie, error) {
-	return trie.NewSecure(root, db.db)
+	tr, err := trie.NewSecure(root, db.db)
+	if err != nil {
+		return nil, err
+	}
+	return tr, nil
 }
 
 // OpenStorageTrie opens the storage trie of an account.
 func (db *cachingDB) OpenStorageTrie(addrHash, root common.Hash) (Trie, error) {
-	return trie.NewSecure(root, db.db)
+	tr, err := trie.NewSecure(root, db.db)
+	if err != nil {
+		return nil, err
+	}
+	return tr, nil
 }
 
 // CopyTrie returns an independent copy of the given trie.

core/state/state_object.go

@@ -156,6 +156,14 @@ func (s *stateObject) touch() {
 }
 
 func (s *stateObject) getTrie(db Database) Trie {
+	if s.trie == nil {
+		// Try fetching from prefetcher first
+		// We don't prefetch empty tries
+		if s.data.Root != emptyRoot && s.db.prefetcher != nil {
+			// When the miner is creating the pending state, there is no
+			// prefetcher
+			s.trie = s.db.prefetcher.trie(s.data.Root)
+		}
 		if s.trie == nil {
 			var err error
 			s.trie, err = db.OpenStorageTrie(s.addrHash, s.data.Root)
@@ -164,6 +172,7 @@ func (s *stateObject) getTrie(db Database) Trie {
 				s.setError(fmt.Errorf("can't create storage trie: %v", err))
 			}
 		}
+	}
 	return s.trie
 }
 
@@ -199,10 +208,22 @@ func (s *stateObject) GetCommittedState(db Database, key common.Hash) common.Has
 	var (
 		enc   []byte
 		err   error
+		meter *time.Duration
 	)
+	readStart := time.Now()
+	if metrics.EnabledExpensive {
+		// If the snap is 'under construction', the first lookup may fail. If that
+		// happens, we don't want to double-count the time elapsed. Thus this
+		// dance with the metering.
+		defer func() {
+			if meter != nil {
+				*meter += time.Since(readStart)
+			}
+		}()
+	}
 	if s.db.snap != nil {
 		if metrics.EnabledExpensive {
-			defer func(start time.Time) { s.db.SnapshotStorageReads += time.Since(start) }(time.Now())
+			meter = &s.db.SnapshotStorageReads
 		}
 		// If the object was destructed in *this* block (and potentially resurrected),
 		// the storage has been cleared out, and we should *not* consult the previous
@@ -217,8 +238,14 @@ func (s *stateObject) GetCommittedState(db Database, key common.Hash) common.Has
 	}
 	// If snapshot unavailable or reading from it failed, load from the database
 	if s.db.snap == nil || err != nil {
+		if meter != nil {
+			// If we already spent time checking the snapshot, account for it
+			// and reset the readStart
+			*meter += time.Since(readStart)
+			readStart = time.Now()
+		}
 		if metrics.EnabledExpensive {
-			defer func(start time.Time) { s.db.StorageReads += time.Since(start) }(time.Now())
+			meter = &s.db.StorageReads
 		}
 		if enc, err = s.getTrie(db).TryGet(key.Bytes()); err != nil {
 			s.setError(err)
@@ -282,9 +309,16 @@ func (s *stateObject) setState(key, value common.Hash) {
 
 // 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() {
+func (s *stateObject) finalise(prefetch bool) {
+	slotsToPrefetch := make([][]byte, 0, len(s.dirtyStorage))
 	for key, value := range s.dirtyStorage {
 		s.pendingStorage[key] = value
+		if value != s.originStorage[key] {
+			slotsToPrefetch = append(slotsToPrefetch, common.CopyBytes(key[:])) // Copy needed for closure
+		}
+	}
+	if s.db.prefetcher != nil && prefetch && len(slotsToPrefetch) > 0 && s.data.Root != emptyRoot {
+		s.db.prefetcher.prefetch(s.data.Root, slotsToPrefetch)
 	}
 	if len(s.dirtyStorage) > 0 {
 		s.dirtyStorage = make(Storage)
@@ -295,7 +329,7 @@ func (s *stateObject) finalise() {
 // It will return nil if the trie has not been loaded and no changes have been made
 func (s *stateObject) updateTrie(db Database) Trie {
 	// Make sure all dirty slots are finalized into the pending storage area
-	s.finalise()
+	s.finalise(false) // Don't prefetch any more, pull directly if need be
 	if len(s.pendingStorage) == 0 {
 		return s.trie
 	}
@@ -303,18 +337,13 @@ func (s *stateObject) updateTrie(db Database) Trie {
 	if metrics.EnabledExpensive {
 		defer func(start time.Time) { s.db.StorageUpdates += time.Since(start) }(time.Now())
 	}
-	// Retrieve the snapshot storage map for the object
+	// The snapshot storage map for the object
 	var storage map[common.Hash][]byte
-	if s.db.snap != nil {
-		// Retrieve the old storage map, if available, create a new one otherwise
-		storage = s.db.snapStorage[s.addrHash]
-		if storage == nil {
-			storage = make(map[common.Hash][]byte)
-			s.db.snapStorage[s.addrHash] = storage
-		}
-	}
 	// Insert all the pending updates into the trie
 	tr := s.getTrie(db)
+	hasher := s.db.hasher
+
+	usedStorage := make([][]byte, 0, len(s.pendingStorage))
 	for key, value := range s.pendingStorage {
 		// Skip noop changes, persist actual changes
 		if value == s.originStorage[key] {
@@ -331,10 +360,21 @@ func (s *stateObject) updateTrie(db Database) Trie {
 			s.setError(tr.TryUpdate(key[:], v))
 		}
 		// If state snapshotting is active, cache the data til commit
-		if storage != nil {
+		if s.db.snap != nil {
-			storage[crypto.Keccak256Hash(key[:])] = v // v will be nil if value is 0x00
+			if storage == nil {
+				// Retrieve the old storage map, if available, create a new one otherwise
+				if storage = s.db.snapStorage[s.addrHash]; storage == nil {
+					storage = make(map[common.Hash][]byte)
+					s.db.snapStorage[s.addrHash] = storage
 				}
 			}
+			storage[crypto.HashData(hasher, key[:])] = v // v will be nil if value is 0x00
+		}
+		usedStorage = append(usedStorage, common.CopyBytes(key[:])) // Copy needed for closure
+	}
+	if s.db.prefetcher != nil {
+		s.db.prefetcher.used(s.data.Root, usedStorage)
+	}
 	if len(s.pendingStorage) > 0 {
 		s.pendingStorage = make(Storage)
 	}

core/state/state_test.go

@@ -170,7 +170,7 @@ func TestSnapshot2(t *testing.T) {
 	state.setStateObject(so0)
 
 	root, _ := state.Commit(false)
-	state.Reset(root)
+	state, _ = New(root, state.db, state.snaps)
 
 	// and one with deleted == true
 	so1 := state.getStateObject(stateobjaddr1)

core/state/statedb.go

@@ -63,7 +63,10 @@ func (n *proofList) Delete(key []byte) error {
 // * Accounts
 type StateDB struct {
 	db           Database
+	prefetcher   *triePrefetcher
+	originalRoot common.Hash // The pre-state root, before any changes were made
 	trie         Trie
+	hasher       crypto.KeccakState
 
 	snaps         *snapshot.Tree
 	snap          snapshot.Snapshot
@@ -125,6 +128,7 @@ func New(root common.Hash, db Database, snaps *snapshot.Tree) (*StateDB, error)
 	sdb := &StateDB{
 		db:                  db,
 		trie:                tr,
+		originalRoot:        root,
 		snaps:               snaps,
 		stateObjects:        make(map[common.Address]*stateObject),
 		stateObjectsPending: make(map[common.Address]struct{}),
@@ -133,6 +137,7 @@ func New(root common.Hash, db Database, snaps *snapshot.Tree) (*StateDB, error)
 		preimages:           make(map[common.Hash][]byte),
 		journal:             newJournal(),
 		accessList:          newAccessList(),
+		hasher:              crypto.NewKeccakState(),
 	}
 	if sdb.snaps != nil {
 		if sdb.snap = sdb.snaps.Snapshot(root); sdb.snap != nil {
@@ -144,6 +149,28 @@ func New(root common.Hash, db Database, snaps *snapshot.Tree) (*StateDB, error)
 	return sdb, nil
 }
 
+// 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) {
+	if s.prefetcher != nil {
+		s.prefetcher.close()
+		s.prefetcher = nil
+	}
+	if s.snap != nil {
+		s.prefetcher = newTriePrefetcher(s.db, s.originalRoot, namespace)
+	}
+}
+
+// StopPrefetcher terminates a running prefetcher and reports any leftover stats
+// from the gathered metrics.
+func (s *StateDB) StopPrefetcher() {
+	if s.prefetcher != nil {
+		s.prefetcher.close()
+		s.prefetcher = nil
+	}
+}
+
 // setError remembers the first non-nil error it is called with.
 func (s *StateDB) setError(err error) {
 	if s.dbErr == nil {
@@ -155,37 +182,6 @@ func (s *StateDB) Error() error {
 	return s.dbErr
 }
 
-// Reset clears out all ephemeral state objects from the state db, but keeps
-// the underlying state trie to avoid reloading data for the next operations.
-func (s *StateDB) Reset(root common.Hash) error {
-	tr, err := s.db.OpenTrie(root)
-	if err != nil {
-		return err
-	}
-	s.trie = tr
-	s.stateObjects = make(map[common.Address]*stateObject)
-	s.stateObjectsPending = make(map[common.Address]struct{})
-	s.stateObjectsDirty = make(map[common.Address]struct{})
-	s.thash = common.Hash{}
-	s.bhash = common.Hash{}
-	s.txIndex = 0
-	s.logs = make(map[common.Hash][]*types.Log)
-	s.logSize = 0
-	s.preimages = make(map[common.Hash][]byte)
-	s.clearJournalAndRefund()
-
-	if s.snaps != nil {
-		s.snapAccounts, s.snapDestructs, s.snapStorage = nil, nil, nil
-		if s.snap = s.snaps.Snapshot(root); s.snap != nil {
-			s.snapDestructs = make(map[common.Hash]struct{})
-			s.snapAccounts = make(map[common.Hash][]byte)
-			s.snapStorage = make(map[common.Hash]map[common.Hash][]byte)
-		}
-	}
-	s.accessList = newAccessList()
-	return nil
-}
-
 func (s *StateDB) AddLog(log *types.Log) {
 	s.journal.append(addLogChange{txhash: s.thash})
 
@@ -532,7 +528,7 @@ func (s *StateDB) getDeletedStateObject(addr common.Address) *stateObject {
 			defer func(start time.Time) { s.SnapshotAccountReads += time.Since(start) }(time.Now())
 		}
 		var acc *snapshot.Account
-		if acc, err = s.snap.Account(crypto.Keccak256Hash(addr.Bytes())); err == nil {
+		if acc, err = s.snap.Account(crypto.HashData(s.hasher, addr.Bytes())); err == nil {
 			if acc == nil {
 				return nil
 			}
@@ -675,6 +671,7 @@ func (s *StateDB) Copy() *StateDB {
 		logSize:             s.logSize,
 		preimages:           make(map[common.Hash][]byte, len(s.preimages)),
 		journal:             newJournal(),
+		hasher:              crypto.NewKeccakState(),
 	}
 	// Copy the dirty states, logs, and preimages
 	for addr := range s.journal.dirties {
@@ -724,6 +721,13 @@ func (s *StateDB) Copy() *StateDB {
 	// However, it doesn't cost us much to copy an empty list, so we do it anyway
 	// to not blow up if we ever decide copy it in the middle of a transaction
 	state.accessList = s.accessList.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
 }
 
@@ -760,6 +764,7 @@ func (s *StateDB) GetRefund() uint64 {
 // the journal as well as the refunds. Finalise, however, will not push any updates
 // into the tries just yet. Only IntermediateRoot or Commit will do that.
 func (s *StateDB) Finalise(deleteEmptyObjects bool) {
+	addressesToPrefetch := make([][]byte, 0, len(s.journal.dirties))
 	for addr := range s.journal.dirties {
 		obj, exist := s.stateObjects[addr]
 		if !exist {
@@ -784,10 +789,18 @@ func (s *StateDB) Finalise(deleteEmptyObjects bool) {
 				delete(s.snapStorage, obj.addrHash)        // Clear out any previously updated storage data (may be recreated via a ressurrect)
 			}
 		} else {
-			obj.finalise()
+			obj.finalise(true) // Prefetch slots in the background
 		}
 		s.stateObjectsPending[addr] = struct{}{}
 		s.stateObjectsDirty[addr] = struct{}{}
+
+		// At this point, also ship the address off to the precacher. The precacher
+		// will start loading tries, and when the change is eventually committed,
+		// the commit-phase will be a lot faster
+		addressesToPrefetch = append(addressesToPrefetch, common.CopyBytes(addr[:])) // Copy needed for closure
+	}
+	if s.prefetcher != nil && len(addressesToPrefetch) > 0 {
+		s.prefetcher.prefetch(s.originalRoot, addressesToPrefetch)
 	}
 	// Invalidate journal because reverting across transactions is not allowed.
 	s.clearJournalAndRefund()
@@ -800,14 +813,49 @@ 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
+	// modified after we start retrieving tries. Remove it from the statedb after
+	// 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 {
+		defer func() {
+			s.prefetcher.close()
+			s.prefetcher = nil
+		}()
+	}
+	// Although naively it makes sense to retrieve the account trie and then do
+	// the contract storage and account updates sequentially, that short circuits
+	// the account prefetcher. Instead, let's process all the storage updates
+	// first, giving the account prefeches just a few more milliseconds of time
+	// to pull useful data from disk.
 	for addr := range s.stateObjectsPending {
-		obj := s.stateObjects[addr]
+		if obj := s.stateObjects[addr]; !obj.deleted {
-		if obj.deleted {
+			obj.updateRoot(s.db)
+		}
+	}
+	// 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 {
+		if trie := prefetcher.trie(s.originalRoot); trie != nil {
+			s.trie = trie
+		}
+	}
+	usedAddrs := make([][]byte, 0, len(s.stateObjectsPending))
+	for addr := range s.stateObjectsPending {
+		if obj := s.stateObjects[addr]; obj.deleted {
 			s.deleteStateObject(obj)
 		} else {
-			obj.updateRoot(s.db)
 			s.updateStateObject(obj)
 		}
+		usedAddrs = append(usedAddrs, common.CopyBytes(addr[:])) // Copy needed for closure
+	}
+	if prefetcher != nil {
+		prefetcher.used(s.originalRoot, usedAddrs)
 	}
 	if len(s.stateObjectsPending) > 0 {
 		s.stateObjectsPending = make(map[common.Address]struct{})

core/state/statedb_test.go

@@ -474,7 +474,7 @@ func TestTouchDelete(t *testing.T) {
 	s := newStateTest()
 	s.state.GetOrNewStateObject(common.Address{})
 	root, _ := s.state.Commit(false)
-	s.state.Reset(root)
+	s.state, _ = New(root, s.state.db, s.state.snaps)
 
 	snapshot := s.state.Snapshot()
 	s.state.AddBalance(common.Address{}, new(big.Int))
@@ -676,7 +676,7 @@ func TestDeleteCreateRevert(t *testing.T) {
 	state.SetBalance(addr, big.NewInt(1))
 
 	root, _ := state.Commit(false)
-	state.Reset(root)
+	state, _ = New(root, state.db, state.snaps)
 
 	// Simulate self-destructing in one transaction, then create-reverting in another
 	state.Suicide(addr)
@@ -688,7 +688,7 @@ func TestDeleteCreateRevert(t *testing.T) {
 
 	// Commit the entire state and make sure we don't crash and have the correct state
 	root, _ = state.Commit(true)
-	state.Reset(root)
+	state, _ = New(root, state.db, state.snaps)
 
 	if state.getStateObject(addr) != nil {
 		t.Fatalf("self-destructed contract came alive")

core/state/trie_prefetcher.go

@@ -0,0 +1,334 @@
+// Copyright 2020 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package state
+
+import (
+	"sync"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/log"
+	"github.com/ethereum/go-ethereum/metrics"
+)
+
+var (
+	// triePrefetchMetricsPrefix is the prefix under which to publis the metrics.
+	triePrefetchMetricsPrefix = "trie/prefetch/"
+)
+
+// triePrefetcher is an active prefetcher, which receives accounts or storage
+// items and does trie-loading of them. The goal is to get as much useful content
+// into the caches as possible.
+//
+// Note, the prefetcher's API is not thread safe.
+type triePrefetcher struct {
+	db       Database                    // Database to fetch trie nodes through
+	root     common.Hash                 // Root hash of theaccount trie for metrics
+	fetches  map[common.Hash]Trie        // Partially or fully fetcher tries
+	fetchers map[common.Hash]*subfetcher // Subfetchers for each trie
+
+	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
+}
+
+// newTriePrefetcher
+func newTriePrefetcher(db Database, root common.Hash, namespace string) *triePrefetcher {
+	prefix := triePrefetchMetricsPrefix + namespace
+	p := &triePrefetcher{
+		db:       db,
+		root:     root,
+		fetchers: make(map[common.Hash]*subfetcher), // Active prefetchers use the fetchers map
+
+		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
+// and reports the stats to the metrics subsystem.
+func (p *triePrefetcher) close() {
+	for _, fetcher := range p.fetchers {
+		fetcher.abort() // safe to do multiple times
+
+		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))
+				}
+				p.accountWasteMeter.Mark(int64(len(fetcher.seen)))
+			} 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))
+				}
+				p.storageWasteMeter.Mark(int64(len(fetcher.seen)))
+			}
+		}
+	}
+	// 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
+// already loaded will be copied over, but no goroutines will be started. This
+// is mostly used in the miner which creates a copy of it's actively mutated
+// state to be sealed while it may further mutate the state.
+func (p *triePrefetcher) copy() *triePrefetcher {
+	copy := &triePrefetcher{
+		db:      p.db,
+		root:    p.root,
+		fetches: make(map[common.Hash]Trie), // Active prefetchers use the fetches map
+
+		deliveryMissMeter: p.deliveryMissMeter,
+		accountLoadMeter:  p.accountLoadMeter,
+		accountDupMeter:   p.accountDupMeter,
+		accountSkipMeter:  p.accountSkipMeter,
+		accountWasteMeter: p.accountWasteMeter,
+		storageLoadMeter:  p.storageLoadMeter,
+		storageDupMeter:   p.storageDupMeter,
+		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 {
+			copy.fetches[root] = p.db.CopyTrie(fetch)
+		}
+		return copy
+	}
+	// Otherwise we're copying an active fetcher, retrieve the current states
+	for root, fetcher := range p.fetchers {
+		copy.fetches[root] = fetcher.peek()
+	}
+	return copy
+}
+
+// prefetch schedules a batch of trie items to prefetch.
+func (p *triePrefetcher) prefetch(root common.Hash, keys [][]byte) {
+	// If the prefetcher is an inactive one, bail out
+	if p.fetches != nil {
+		return
+	}
+	// Active fetcher, schedule the retrievals
+	fetcher := p.fetchers[root]
+	if fetcher == nil {
+		fetcher = newSubfetcher(p.db, root)
+		p.fetchers[root] = fetcher
+	}
+	fetcher.schedule(keys)
+}
+
+// trie returns the trie matching the root hash, or nil if the prefetcher doesn't
+// have it.
+func (p *triePrefetcher) trie(root common.Hash) Trie {
+	// If the prefetcher is inactive, return from existing deep copies
+	if p.fetches != nil {
+		trie := p.fetches[root]
+		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[root]
+	if fetcher == nil {
+		p.deliveryMissMeter.Mark(1)
+		return nil
+	}
+	// Interrupt the prefetcher if it's by any chance still running and return
+	// a copy of any pre-loaded trie.
+	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.
+func (p *triePrefetcher) used(root common.Hash, used [][]byte) {
+	if fetcher := p.fetchers[root]; fetcher != nil {
+		fetcher.used = used
+	}
+}
+
+// subfetcher is a trie fetcher goroutine responsible for pulling entries for a
+// single trie. It is spawned when a new root is encountered and lives until the
+// main prefetcher is paused and either all requested items are processed or if
+// the trie being worked on is retrieved from the prefetcher.
+type subfetcher struct {
+	db   Database    // Database to load trie nodes through
+	root common.Hash // Root hash of the trie to prefetch
+	trie Trie        // Trie being populated with nodes
+
+	tasks [][]byte   // Items queued up for retrieval
+	lock  sync.Mutex // Lock protecting the task queue
+
+	wake chan struct{}  // Wake channel if a new task is scheduled
+	stop chan struct{}  // Channel to interrupt processing
+	term chan struct{}  // Channel to signal iterruption
+	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
+	used [][]byte            // Tracks the entries used in the end
+}
+
+// newSubfetcher creates a goroutine to prefetch state items belonging to a
+// particular root hash.
+func newSubfetcher(db Database, root common.Hash) *subfetcher {
+	sf := &subfetcher{
+		db:   db,
+		root: root,
+		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()
+	return sf
+}
+
+// schedule adds a batch of trie keys to the queue to prefetch.
+func (sf *subfetcher) schedule(keys [][]byte) {
+	// 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
+	select {
+	case sf.wake <- struct{}{}:
+	default:
+	}
+}
+
+// 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)
+	}
+}
+
+// abort interrupts the subfetcher immediately. It is safe to call abort multiple
+// times but it is not thread safe.
+func (sf *subfetcher) abort() {
+	select {
+	case <-sf.stop:
+	default:
+		close(sf.stop)
+	}
+	<-sf.term
+}
+
+// loop waits for new tasks to be scheduled and keeps loading them until it runs
+// out of tasks or its underlying trie is retrieved for committing.
+func (sf *subfetcher) loop() {
+	// No matter how the loop stops, signal anyone waiting that it's terminated
+	defer close(sf.term)
+
+	// Start by opening the trie and stop processing if it fails
+	trie, err := sf.db.OpenTrie(sf.root)
+	if err != nil {
+		log.Warn("Trie prefetcher failed opening trie", "root", sf.root, "err", err)
+		return
+	}
+	sf.trie = trie
+
+	// Trie opened successfully, keep prefetching items
+	for {
+		select {
+		case <-sf.wake:
+			// Subfetcher was woken up, retrieve any tasks to avoid spinning the lock
+			sf.lock.Lock()
+			tasks := sf.tasks
+			sf.tasks = nil
+			sf.lock.Unlock()
+
+			// Prefetch any tasks until the loop is interrupted
+			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
+					taskid := string(task)
+					if _, ok := sf.seen[taskid]; ok {
+						sf.dups++
+					} else {
+						sf.trie.TryGet(task)
+						sf.seen[taskid] = 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
+			return
+		}
+	}
+}

crypto/crypto.go

@@ -60,10 +60,23 @@ type KeccakState interface {
 	Read([]byte) (int, error)
 }
 
+// NewKeccakState creates a new KeccakState
+func NewKeccakState() KeccakState {
+	return sha3.NewLegacyKeccak256().(KeccakState)
+}
+
+// HashData hashes the provided data using the KeccakState and returns a 32 byte hash
+func HashData(kh KeccakState, data []byte) (h common.Hash) {
+	kh.Reset()
+	kh.Write(data)
+	kh.Read(h[:])
+	return h
+}
+
 // Keccak256 calculates and returns the Keccak256 hash of the input data.
 func Keccak256(data ...[]byte) []byte {
 	b := make([]byte, 32)
-	d := sha3.NewLegacyKeccak256().(KeccakState)
+	d := NewKeccakState()
 	for _, b := range data {
 		d.Write(b)
 	}
@@ -74,7 +87,7 @@ func Keccak256(data ...[]byte) []byte {
 // Keccak256Hash calculates and returns the Keccak256 hash of the input data,
 // converting it to an internal Hash data structure.
 func Keccak256Hash(data ...[]byte) (h common.Hash) {
-	d := sha3.NewLegacyKeccak256().(KeccakState)
+	d := NewKeccakState()
 	for _, b := range data {
 		d.Write(b)
 	}

crypto/crypto_test.go

@@ -42,6 +42,13 @@ func TestKeccak256Hash(t *testing.T) {
 	checkhash(t, "Sha3-256-array", func(in []byte) []byte { h := Keccak256Hash(in); return h[:] }, msg, exp)
 }
 
+func TestKeccak256Hasher(t *testing.T) {
+	msg := []byte("abc")
+	exp, _ := hex.DecodeString("4e03657aea45a94fc7d47ba826c8d667c0d1e6e33a64a036ec44f58fa12d6c45")
+	hasher := NewKeccakState()
+	checkhash(t, "Sha3-256-array", func(in []byte) []byte { h := HashData(hasher, in); return h[:] }, msg, exp)
+}
+
 func TestToECDSAErrors(t *testing.T) {
 	if _, err := HexToECDSA("0000000000000000000000000000000000000000000000000000000000000000"); err == nil {
 		t.Fatal("HexToECDSA should've returned error")

eth/api_tracer.go

@@ -299,7 +299,8 @@ func (api *PrivateDebugAPI) traceChain(ctx context.Context, start, end *types.Bl
 				failed = err
 				break
 			}
-			if err := statedb.Reset(root); err != nil {
+			statedb, err = state.New(root, database, nil)
+			if err != nil {
 				failed = err
 				break
 			}
@@ -699,7 +700,8 @@ func (api *PrivateDebugAPI) computeStateDB(block *types.Block, reexec uint64) (*
 		if err != nil {
 			return nil, err
 		}
-		if err := statedb.Reset(root); err != nil {
+		statedb, err = state.New(root, database, nil)
+		if err != nil {
 			return nil, fmt.Errorf("state reset after block %d failed: %v", block.NumberU64(), err)
 		}
 		database.TrieDB().Reference(root, common.Hash{})

miner/worker.go

@@ -303,6 +303,9 @@ func (w *worker) isRunning() bool {
 // close terminates all background threads maintained by the worker.
 // Note the worker does not support being closed multiple times.
 func (w *worker) close() {
+	if w.current != nil && w.current.state != nil {
+		w.current.state.StopPrefetcher()
+	}
 	atomic.StoreInt32(&w.running, 0)
 	close(w.exitCh)
 }
@@ -642,10 +645,14 @@ func (w *worker) resultLoop() {
 
 // makeCurrent creates a new environment for the current cycle.
 func (w *worker) makeCurrent(parent *types.Block, header *types.Header) error {
+	// Retrieve the parent state to execute on top and start a prefetcher for
+	// the miner to speed block sealing up a bit
 	state, err := w.chain.StateAt(parent.Root())
 	if err != nil {
 		return err
 	}
+	state.StartPrefetcher("miner")
+
 	env := &environment{
 		signer:    types.NewEIP155Signer(w.chainConfig.ChainID),
 		state:     state,
@@ -654,7 +661,6 @@ func (w *worker) makeCurrent(parent *types.Block, header *types.Header) error {
 		uncles:    mapset.NewSet(),
 		header:    header,
 	}
-
 	// when 08 is processed ancestors contain 07 (quick block)
 	for _, ancestor := range w.chain.GetBlocksFromHash(parent.Hash(), 7) {
 		for _, uncle := range ancestor.Uncles() {
@@ -663,9 +669,14 @@ func (w *worker) makeCurrent(parent *types.Block, header *types.Header) error {
 		env.family.Add(ancestor.Hash())
 		env.ancestors.Add(ancestor.Hash())
 	}
-
 	// Keep track of transactions which return errors so they can be removed
 	env.tcount = 0
+
+	// Swap out the old work with the new one, terminating any leftover prefetcher
+	// processes in the mean time and starting a new one.
+	if w.current != nil && w.current.state != nil {
+		w.current.state.StopPrefetcher()
+	}
 	w.current = env
 	return nil
 }
@@ -719,7 +730,6 @@ func (w *worker) updateSnapshot() {
 		w.current.receipts,
 		new(trie.Trie),
 	)
-
 	w.snapshotState = w.current.state.Copy()
 }