cmd, core, eth, trie: get rid of trie cache generations (#19262)

* cmd, core, eth, trie: get rid of trie cache generations

* core, trie: get rid of remainder of cache gen boilerplate

12 files changed, 52 insertions, 246 deletions

diff --git a/trie/database.go b/trie/database.go
index 73ba2e761..c853dfe51 100644
--- a/trie/database.go
+++ b/trie/database.go
@@ -154,11 +154,11 @@ func (n *cachedNode) rlp() []byte {
 
 // obj returns the decoded and expanded trie node, either directly from the cache,
 // or by regenerating it from the rlp encoded blob.
-func (n *cachedNode) obj(hash common.Hash, cachegen uint16) node {
+func (n *cachedNode) obj(hash common.Hash) node {
 	if node, ok := n.node.(rawNode); ok {
-		return mustDecodeNode(hash[:], node, cachegen)
+		return mustDecodeNode(hash[:], node)
 	}
-	return expandNode(hash[:], n.node, cachegen)
+	return expandNode(hash[:], n.node)
 }
 
 // childs returns all the tracked children of this node, both the implicit ones
@@ -223,16 +223,15 @@ func simplifyNode(n node) node {
 
 // expandNode traverses the node hierarchy of a collapsed storage node and converts
 // all fields and keys into expanded memory form.
-func expandNode(hash hashNode, n node, cachegen uint16) node {
+func expandNode(hash hashNode, n node) node {
 	switch n := n.(type) {
 	case *rawShortNode:
 		// Short nodes need key and child expansion
 		return &shortNode{
 			Key: compactToHex(n.Key),
-			Val: expandNode(nil, n.Val, cachegen),
+			Val: expandNode(nil, n.Val),
 			flags: nodeFlag{
 				hash: hash,
-				gen:  cachegen,
 			},
 		}
 
@@ -241,12 +240,11 @@ func expandNode(hash hashNode, n node, cachegen uint16) node {
 		node := &fullNode{
 			flags: nodeFlag{
 				hash: hash,
-				gen:  cachegen,
 			},
 		}
 		for i := 0; i < len(node.Children); i++ {
 			if n[i] != nil {
-				node.Children[i] = expandNode(nil, n[i], cachegen)
+				node.Children[i] = expandNode(nil, n[i])
 			}
 		}
 		return node
@@ -349,13 +347,13 @@ func (db *Database) insertPreimage(hash common.Hash, preimage []byte) {
 
 // node retrieves a cached trie node from memory, or returns nil if none can be
 // found in the memory cache.
-func (db *Database) node(hash common.Hash, cachegen uint16) node {
+func (db *Database) node(hash common.Hash) node {
 	// Retrieve the node from the clean cache if available
 	if db.cleans != nil {
 		if enc, err := db.cleans.Get(string(hash[:])); err == nil && enc != nil {
 			memcacheCleanHitMeter.Mark(1)
 			memcacheCleanReadMeter.Mark(int64(len(enc)))
-			return mustDecodeNode(hash[:], enc, cachegen)
+			return mustDecodeNode(hash[:], enc)
 		}
 	}
 	// Retrieve the node from the dirty cache if available
@@ -364,7 +362,7 @@ func (db *Database) node(hash common.Hash, cachegen uint16) node {
 	db.lock.RUnlock()
 
 	if dirty != nil {
-		return dirty.obj(hash, cachegen)
+		return dirty.obj(hash)
 	}
 	// Content unavailable in memory, attempt to retrieve from disk
 	enc, err := db.diskdb.Get(hash[:])
@@ -376,7 +374,7 @@ func (db *Database) node(hash common.Hash, cachegen uint16) node {
 		memcacheCleanMissMeter.Mark(1)
 		memcacheCleanWriteMeter.Mark(int64(len(enc)))
 	}
-	return mustDecodeNode(hash[:], enc, cachegen)
+	return mustDecodeNode(hash[:], enc)
 }
 
 // Node retrieves an encoded cached trie node from memory. If it cannot be found
diff --git a/trie/hasher.go b/trie/hasher.go
index 9d6756b6f..54f6a9de2 100644
--- a/trie/hasher.go
+++ b/trie/hasher.go
@@ -26,11 +26,9 @@ import (
 )
 
 type hasher struct {
-	tmp        sliceBuffer
-	sha        keccakState
-	cachegen   uint16
-	cachelimit uint16
-	onleaf     LeafCallback
+	tmp    sliceBuffer
+	sha    keccakState
+	onleaf LeafCallback
 }
 
 // keccakState wraps sha3.state. In addition to the usual hash methods, it also supports
@@ -62,9 +60,9 @@ var hasherPool = sync.Pool{
 	},
 }
 
-func newHasher(cachegen, cachelimit uint16, onleaf LeafCallback) *hasher {
+func newHasher(onleaf LeafCallback) *hasher {
 	h := hasherPool.Get().(*hasher)
-	h.cachegen, h.cachelimit, h.onleaf = cachegen, cachelimit, onleaf
+	h.onleaf = onleaf
 	return h
 }
 
@@ -80,14 +78,13 @@ func (h *hasher) hash(n node, db *Database, force bool) (node, node, error) {
 		if db == nil {
 			return hash, n, nil
 		}
-		if n.canUnload(h.cachegen, h.cachelimit) {
-			// Unload the node from cache. All of its subnodes will have a lower or equal
-			// cache generation number.
-			cacheUnloadCounter.Inc(1)
-			return hash, hash, nil
-		}
 		if !dirty {
-			return hash, n, nil
+			switch n.(type) {
+			case *fullNode, *shortNode:
+				return hash, hash, nil
+			default:
+				return hash, n, nil
+			}
 		}
 	}
 	// Trie not processed yet or needs storage, walk the children
diff --git a/trie/iterator.go b/trie/iterator.go
index 77f168166..da93b2fad 100644
--- a/trie/iterator.go
+++ b/trie/iterator.go
@@ -180,7 +180,7 @@ func (it *nodeIterator) LeafBlob() []byte {
 func (it *nodeIterator) LeafProof() [][]byte {
 	if len(it.stack) > 0 {
 		if _, ok := it.stack[len(it.stack)-1].node.(valueNode); ok {
-			hasher := newHasher(0, 0, nil)
+			hasher := newHasher(nil)
 			defer returnHasherToPool(hasher)
 
 			proofs := make([][]byte, 0, len(it.stack))
diff --git a/trie/node.go b/trie/node.go
index 1fafb7a53..f4055e779 100644
--- a/trie/node.go
+++ b/trie/node.go
@@ -30,7 +30,6 @@ var indices = []string{"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b
 type node interface {
 	fstring(string) string
 	cache() (hashNode, bool)
-	canUnload(cachegen, cachelimit uint16) bool
 }
 
 type (
@@ -71,20 +70,9 @@ func (n *shortNode) copy() *shortNode { copy := *n; return &copy }
 // nodeFlag contains caching-related metadata about a node.
 type nodeFlag struct {
 	hash  hashNode // cached hash of the node (may be nil)
-	gen   uint16   // cache generation counter
 	dirty bool     // whether the node has changes that must be written to the database
 }
 
-// canUnload tells whether a node can be unloaded.
-func (n *nodeFlag) canUnload(cachegen, cachelimit uint16) bool {
-	return !n.dirty && cachegen-n.gen >= cachelimit
-}
-
-func (n *fullNode) canUnload(gen, limit uint16) bool  { return n.flags.canUnload(gen, limit) }
-func (n *shortNode) canUnload(gen, limit uint16) bool { return n.flags.canUnload(gen, limit) }
-func (n hashNode) canUnload(uint16, uint16) bool      { return false }
-func (n valueNode) canUnload(uint16, uint16) bool     { return false }
-
 func (n *fullNode) cache() (hashNode, bool)  { return n.flags.hash, n.flags.dirty }
 func (n *shortNode) cache() (hashNode, bool) { return n.flags.hash, n.flags.dirty }
 func (n hashNode) cache() (hashNode, bool)   { return nil, true }
@@ -117,8 +105,8 @@ func (n valueNode) fstring(ind string) string {
 	return fmt.Sprintf("%x ", []byte(n))
 }
 
-func mustDecodeNode(hash, buf []byte, cachegen uint16) node {
-	n, err := decodeNode(hash, buf, cachegen)
+func mustDecodeNode(hash, buf []byte) node {
+	n, err := decodeNode(hash, buf)
 	if err != nil {
 		panic(fmt.Sprintf("node %x: %v", hash, err))
 	}
@@ -126,7 +114,7 @@ func mustDecodeNode(hash, buf []byte, cachegen uint16) node {
 }
 
 // decodeNode parses the RLP encoding of a trie node.
-func decodeNode(hash, buf []byte, cachegen uint16) (node, error) {
+func decodeNode(hash, buf []byte) (node, error) {
 	if len(buf) == 0 {
 		return nil, io.ErrUnexpectedEOF
 	}
@@ -136,22 +124,22 @@ func decodeNode(hash, buf []byte, cachegen uint16) (node, error) {
 	}
 	switch c, _ := rlp.CountValues(elems); c {
 	case 2:
-		n, err := decodeShort(hash, elems, cachegen)
+		n, err := decodeShort(hash, elems)
 		return n, wrapError(err, "short")
 	case 17:
-		n, err := decodeFull(hash, elems, cachegen)
+		n, err := decodeFull(hash, elems)
 		return n, wrapError(err, "full")
 	default:
 		return nil, fmt.Errorf("invalid number of list elements: %v", c)
 	}
 }
 
-func decodeShort(hash, elems []byte, cachegen uint16) (node, error) {
+func decodeShort(hash, elems []byte) (node, error) {
 	kbuf, rest, err := rlp.SplitString(elems)
 	if err != nil {
 		return nil, err
 	}
-	flag := nodeFlag{hash: hash, gen: cachegen}
+	flag := nodeFlag{hash: hash}
 	key := compactToHex(kbuf)
 	if hasTerm(key) {
 		// value node
@@ -161,17 +149,17 @@ func decodeShort(hash, elems []byte, cachegen uint16) (node, error) {
 		}
 		return &shortNode{key, append(valueNode{}, val...), flag}, nil
 	}
-	r, _, err := decodeRef(rest, cachegen)
+	r, _, err := decodeRef(rest)
 	if err != nil {
 		return nil, wrapError(err, "val")
 	}
 	return &shortNode{key, r, flag}, nil
 }
 
-func decodeFull(hash, elems []byte, cachegen uint16) (*fullNode, error) {
-	n := &fullNode{flags: nodeFlag{hash: hash, gen: cachegen}}
+func decodeFull(hash, elems []byte) (*fullNode, error) {
+	n := &fullNode{flags: nodeFlag{hash: hash}}
 	for i := 0; i < 16; i++ {
-		cld, rest, err := decodeRef(elems, cachegen)
+		cld, rest, err := decodeRef(elems)
 		if err != nil {
 			return n, wrapError(err, fmt.Sprintf("[%d]", i))
 		}
@@ -189,7 +177,7 @@ func decodeFull(hash, elems []byte, cachegen uint16) (*fullNode, error) {
 
 const hashLen = len(common.Hash{})
 
-func decodeRef(buf []byte, cachegen uint16) (node, []byte, error) {
+func decodeRef(buf []byte) (node, []byte, error) {
 	kind, val, rest, err := rlp.Split(buf)
 	if err != nil {
 		return nil, buf, err
@@ -202,7 +190,7 @@ func decodeRef(buf []byte, cachegen uint16) (node, []byte, error) {
 			err := fmt.Errorf("oversized embedded node (size is %d bytes, want size < %d)", size, hashLen)
 			return nil, buf, err
 		}
-		n, err := decodeNode(nil, buf, cachegen)
+		n, err := decodeNode(nil, buf)
 		return n, rest, err
 	case kind == rlp.String && len(val) == 0:
 		// empty node
diff --git a/trie/node_test.go b/trie/node_test.go
deleted file mode 100644
index 7ad1ff9e7..000000000
--- a/trie/node_test.go
+++ /dev/null
@@ -1,58 +0,0 @@
-// Copyright 2016 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 trie
-
-import "testing"
-
-func TestCanUnload(t *testing.T) {
-	tests := []struct {
-		flag                 nodeFlag
-		cachegen, cachelimit uint16
-		want                 bool
-	}{
-		{
-			flag: nodeFlag{dirty: true, gen: 0},
-			want: false,
-		},
-		{
-			flag:     nodeFlag{dirty: false, gen: 0},
-			cachegen: 0, cachelimit: 0,
-			want: true,
-		},
-		{
-			flag:     nodeFlag{dirty: false, gen: 65534},
-			cachegen: 65535, cachelimit: 1,
-			want: true,
-		},
-		{
-			flag:     nodeFlag{dirty: false, gen: 65534},
-			cachegen: 0, cachelimit: 1,
-			want: true,
-		},
-		{
-			flag:     nodeFlag{dirty: false, gen: 1},
-			cachegen: 65535, cachelimit: 1,
-			want: true,
-		},
-	}
-
-	for _, test := range tests {
-		if got := test.flag.canUnload(test.cachegen, test.cachelimit); got != test.want {
-			t.Errorf("%+v\n   got %t, want %t", test, got, test.want)
-		}
-	}
-}
diff --git a/trie/proof.go b/trie/proof.go
index 0f18dd26b..26a41ed27 100644
--- a/trie/proof.go
+++ b/trie/proof.go
@@ -65,7 +65,7 @@ func (t *Trie) Prove(key []byte, fromLevel uint, proofDb ethdb.Writer) error {
 			panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
 		}
 	}
-	hasher := newHasher(0, 0, nil)
+	hasher := newHasher(nil)
 	defer returnHasherToPool(hasher)
 
 	for i, n := range nodes {
@@ -112,7 +112,7 @@ func VerifyProof(rootHash common.Hash, key []byte, proofDb ethdb.Reader) (value
 		if buf == nil {
 			return nil, i, fmt.Errorf("proof node %d (hash %064x) missing", i, wantHash)
 		}
-		n, err := decodeNode(wantHash[:], buf, 0)
+		n, err := decodeNode(wantHash[:], buf)
 		if err != nil {
 			return nil, i, fmt.Errorf("bad proof node %d: %v", i, err)
 		}
diff --git a/trie/secure_trie.go b/trie/secure_trie.go
index 6a50cfd5a..fbc591ed1 100644
--- a/trie/secure_trie.go
+++ b/trie/secure_trie.go
@@ -51,7 +51,7 @@ type SecureTrie struct {
 // Loaded nodes are kept around until their 'cache generation' expires.
 // A new cache generation is created by each call to Commit.
 // cachelimit sets the number of past cache generations to keep.
-func NewSecure(root common.Hash, db *Database, cachelimit uint16) (*SecureTrie, error) {
+func NewSecure(root common.Hash, db *Database) (*SecureTrie, error) {
 	if db == nil {
 		panic("trie.NewSecure called without a database")
 	}
@@ -59,7 +59,6 @@ func NewSecure(root common.Hash, db *Database, cachelimit uint16) (*SecureTrie,
 	if err != nil {
 		return nil, err
 	}
-	trie.SetCacheLimit(cachelimit)
 	return &SecureTrie{trie: *trie}, nil
 }
 
@@ -161,12 +160,6 @@ func (t *SecureTrie) Hash() common.Hash {
 	return t.trie.Hash()
 }
 
-// Root returns the root hash of SecureTrie.
-// Deprecated: use Hash instead.
-func (t *SecureTrie) Root() []byte {
-	return t.trie.Root()
-}
-
 // Copy returns a copy of SecureTrie.
 func (t *SecureTrie) Copy() *SecureTrie {
 	cpy := *t
@@ -183,7 +176,7 @@ func (t *SecureTrie) NodeIterator(start []byte) NodeIterator {
 // The caller must not hold onto the return value because it will become
 // invalid on the next call to hashKey or secKey.
 func (t *SecureTrie) hashKey(key []byte) []byte {
-	h := newHasher(0, 0, nil)
+	h := newHasher(nil)
 	h.sha.Reset()
 	h.sha.Write(key)
 	buf := h.sha.Sum(t.hashKeyBuf[:0])
diff --git a/trie/secure_trie_test.go b/trie/secure_trie_test.go
index f0ca6c800..fb6c38ee2 100644
--- a/trie/secure_trie_test.go
+++ b/trie/secure_trie_test.go
@@ -28,7 +28,7 @@ import (
 )
 
 func newEmptySecure() *SecureTrie {
-	trie, _ := NewSecure(common.Hash{}, NewDatabase(memorydb.New()), 0)
+	trie, _ := NewSecure(common.Hash{}, NewDatabase(memorydb.New()))
 	return trie
 }
 
@@ -36,8 +36,7 @@ func newEmptySecure() *SecureTrie {
 func makeTestSecureTrie() (*Database, *SecureTrie, map[string][]byte) {
 	// Create an empty trie
 	triedb := NewDatabase(memorydb.New())
-
-	trie, _ := NewSecure(common.Hash{}, triedb, 0)
+	trie, _ := NewSecure(common.Hash{}, triedb)
 
 	// Fill it with some arbitrary data
 	content := make(map[string][]byte)
diff --git a/trie/sync.go b/trie/sync.go
index ef931f633..85f1b0f85 100644
--- a/trie/sync.go
+++ b/trie/sync.go
@@ -101,7 +101,7 @@ func (s *Sync) AddSubTrie(root common.Hash, depth int, parent common.Hash, callb
 	}
 	key := root.Bytes()
 	blob, _ := s.database.Get(key)
-	if local, err := decodeNode(key, blob, 0); local != nil && err == nil {
+	if local, err := decodeNode(key, blob); local != nil && err == nil {
 		return
 	}
 	// Assemble the new sub-trie sync request
@@ -187,7 +187,7 @@ func (s *Sync) Process(results []SyncResult) (bool, int, error) {
 			continue
 		}
 		// Decode the node data content and update the request
-		node, err := decodeNode(item.Hash[:], item.Data, 0)
+		node, err := decodeNode(item.Hash[:], item.Data)
 		if err != nil {
 			return committed, i, err
 		}
diff --git a/trie/sync_test.go b/trie/sync_test.go
index d80070f3e..0d8c29cfe 100644
--- a/trie/sync_test.go
+++ b/trie/sync_test.go
@@ -133,7 +133,7 @@ func testIterativeSync(t *testing.T, batch int) {
 		queue = append(queue[:0], sched.Missing(batch)...)
 	}
 	// Cross check that the two tries are in sync
-	checkTrieContents(t, triedb, srcTrie.Root(), srcData)
+	checkTrieContents(t, triedb, srcTrie.Hash().Bytes(), srcData)
 }
 
 // Tests that the trie scheduler can correctly reconstruct the state even if only
@@ -167,7 +167,7 @@ func TestIterativeDelayedSync(t *testing.T) {
 		queue = append(queue[len(results):], sched.Missing(10000)...)
 	}
 	// Cross check that the two tries are in sync
-	checkTrieContents(t, triedb, srcTrie.Root(), srcData)
+	checkTrieContents(t, triedb, srcTrie.Hash().Bytes(), srcData)
 }
 
 // Tests that given a root hash, a trie can sync iteratively on a single thread,
@@ -212,7 +212,7 @@ func testIterativeRandomSync(t *testing.T, batch int) {
 		}
 	}
 	// Cross check that the two tries are in sync
-	checkTrieContents(t, triedb, srcTrie.Root(), srcData)
+	checkTrieContents(t, triedb, srcTrie.Hash().Bytes(), srcData)
 }
 
 // Tests that the trie scheduler can correctly reconstruct the state even if only
@@ -259,7 +259,7 @@ func TestIterativeRandomDelayedSync(t *testing.T) {
 		}
 	}
 	// Cross check that the two tries are in sync
-	checkTrieContents(t, triedb, srcTrie.Root(), srcData)
+	checkTrieContents(t, triedb, srcTrie.Hash().Bytes(), srcData)
 }
 
 // Tests that a trie sync will not request nodes multiple times, even if they
@@ -299,7 +299,7 @@ func TestDuplicateAvoidanceSync(t *testing.T) {
 		queue = append(queue[:0], sched.Missing(0)...)
 	}
 	// Cross check that the two tries are in sync
-	checkTrieContents(t, triedb, srcTrie.Root(), srcData)
+	checkTrieContents(t, triedb, srcTrie.Hash().Bytes(), srcData)
 }
 
 // Tests that at any point in time during a sync, only complete sub-tries are in
diff --git a/trie/trie.go b/trie/trie.go
index af424d4ac..920e331fd 100644
--- a/trie/trie.go
+++ b/trie/trie.go
@@ -24,7 +24,6 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/log"
-	"github.com/ethereum/go-ethereum/metrics"
 )
 
 var (
@@ -35,25 +34,6 @@ var (
 	emptyState = crypto.Keccak256Hash(nil)
 )
 
-var (
-	cacheMissCounter   = metrics.NewRegisteredCounter("trie/cachemiss", nil)
-	cacheUnloadCounter = metrics.NewRegisteredCounter("trie/cacheunload", nil)
-)
-
-// CacheMisses retrieves a global counter measuring the number of cache misses
-// the trie had since process startup. This isn't useful for anything apart from
-// trie debugging purposes.
-func CacheMisses() int64 {
-	return cacheMissCounter.Count()
-}
-
-// CacheUnloads retrieves a global counter measuring the number of cache unloads
-// the trie did since process startup. This isn't useful for anything apart from
-// trie debugging purposes.
-func CacheUnloads() int64 {
-	return cacheUnloadCounter.Count()
-}
-
 // LeafCallback is a callback type invoked when a trie operation reaches a leaf
 // node. It's used by state sync and commit to allow handling external references
 // between account and storage tries.
@@ -67,23 +47,11 @@ type LeafCallback func(leaf []byte, parent common.Hash) error
 type Trie struct {
 	db   *Database
 	root node
-
-	// Cache generation values.
-	// cachegen increases by one with each commit operation.
-	// new nodes are tagged with the current generation and unloaded
-	// when their generation is older than than cachegen-cachelimit.
-	cachegen, cachelimit uint16
-}
-
-// SetCacheLimit sets the number of 'cache generations' to keep.
-// A cache generation is created by a call to Commit.
-func (t *Trie) SetCacheLimit(l uint16) {
-	t.cachelimit = l
 }
 
 // newFlag returns the cache flag value for a newly created node.
 func (t *Trie) newFlag() nodeFlag {
-	return nodeFlag{dirty: true, gen: t.cachegen}
+	return nodeFlag{dirty: true}
 }
 
 // New creates a trie with an existing root node from db.
@@ -152,14 +120,12 @@ func (t *Trie) tryGet(origNode node, key []byte, pos int) (value []byte, newnode
 		if err == nil && didResolve {
 			n = n.copy()
 			n.Val = newnode
-			n.flags.gen = t.cachegen
 		}
 		return value, n, didResolve, err
 	case *fullNode:
 		value, newnode, didResolve, err = t.tryGet(n.Children[key[pos]], key, pos+1)
 		if err == nil && didResolve {
 			n = n.copy()
-			n.flags.gen = t.cachegen
 			n.Children[key[pos]] = newnode
 		}
 		return value, n, didResolve, err
@@ -428,19 +394,13 @@ func (t *Trie) resolve(n node, prefix []byte) (node, error) {
 }
 
 func (t *Trie) resolveHash(n hashNode, prefix []byte) (node, error) {
-	cacheMissCounter.Inc(1)
-
 	hash := common.BytesToHash(n)
-	if node := t.db.node(hash, t.cachegen); node != nil {
+	if node := t.db.node(hash); node != nil {
 		return node, nil
 	}
 	return nil, &MissingNodeError{NodeHash: hash, Path: prefix}
 }
 
-// Root returns the root hash of the trie.
-// Deprecated: use Hash instead.
-func (t *Trie) Root() []byte { return t.Hash().Bytes() }
-
 // Hash returns the root hash of the trie. It does not write to the
 // database and can be used even if the trie doesn't have one.
 func (t *Trie) Hash() common.Hash {
@@ -460,7 +420,6 @@ func (t *Trie) Commit(onleaf LeafCallback) (root common.Hash, err error) {
 		return common.Hash{}, err
 	}
 	t.root = cached
-	t.cachegen++
 	return common.BytesToHash(hash.(hashNode)), nil
 }
 
@@ -468,7 +427,7 @@ func (t *Trie) hashRoot(db *Database, onleaf LeafCallback) (node, node, error) {
 	if t.root == nil {
 		return hashNode(emptyRoot.Bytes()), nil, nil
 	}
-	h := newHasher(t.cachegen, t.cachelimit, onleaf)
+	h := newHasher(onleaf)
 	defer returnHasherToPool(h)
 	return h.hash(t.root, db, true)
 }
diff --git a/trie/trie_test.go b/trie/trie_test.go
index 1c874370c..ea0b3cbdd 100644
--- a/trie/trie_test.go
+++ b/trie/trie_test.go
@@ -19,7 +19,6 @@ package trie
 import (
 	"bytes"
 	"encoding/binary"
-	"errors"
 	"fmt"
 	"io/ioutil"
 	"math/big"
@@ -328,38 +327,6 @@ func (db *countingDB) Get(key []byte) ([]byte, error) {
 	return db.KeyValueStore.Get(key)
 }
 
-// TestCacheUnload checks that decoded nodes are unloaded after a
-// certain number of commit operations.
-func TestCacheUnload(t *testing.T) {
-	// Create test trie with two branches.
-	trie := newEmpty()
-	key1 := "---------------------------------"
-	key2 := "---some other branch"
-	updateString(trie, key1, "this is the branch of key1.")
-	updateString(trie, key2, "this is the branch of key2.")
-
-	root, _ := trie.Commit(nil)
-	trie.db.Commit(root, true)
-
-	// Commit the trie repeatedly and access key1.
-	// The branch containing it is loaded from DB exactly two times:
-	// in the 0th and 6th iteration.
-	diskdb := &countingDB{KeyValueStore: trie.db.diskdb, gets: make(map[string]int)}
-	triedb := NewDatabase(diskdb)
-	trie, _ = New(root, triedb)
-	trie.SetCacheLimit(5)
-	for i := 0; i < 12; i++ {
-		getString(trie, key1)
-		trie.Commit(nil)
-	}
-	// Check that it got loaded two times.
-	for dbkey, count := range diskdb.gets {
-		if count != 2 {
-			t.Errorf("db key %x loaded %d times, want %d times", []byte(dbkey), count, 2)
-		}
-	}
-}
-
 // randTest performs random trie operations.
 // Instances of this test are created by Generate.
 type randTest []randTestStep
@@ -379,7 +346,6 @@ const (
 	opHash
 	opReset
 	opItercheckhash
-	opCheckCacheInvariant
 	opMax // boundary value, not an actual op
 )
 
@@ -458,8 +424,6 @@ func runRandTest(rt randTest) bool {
 			if tr.Hash() != checktr.Hash() {
 				rt[i].err = fmt.Errorf("hash mismatch in opItercheckhash")
 			}
-		case opCheckCacheInvariant:
-			rt[i].err = checkCacheInvariant(tr.root, nil, tr.cachegen, false, 0)
 		}
 		// Abort the test on error.
 		if rt[i].err != nil {
@@ -469,40 +433,6 @@ func runRandTest(rt randTest) bool {
 	return true
 }
 
-func checkCacheInvariant(n, parent node, parentCachegen uint16, parentDirty bool, depth int) error {
-	var children []node
-	var flag nodeFlag
-	switch n := n.(type) {
-	case *shortNode:
-		flag = n.flags
-		children = []node{n.Val}
-	case *fullNode:
-		flag = n.flags
-		children = n.Children[:]
-	default:
-		return nil
-	}
-
-	errorf := func(format string, args ...interface{}) error {
-		msg := fmt.Sprintf(format, args...)
-		msg += fmt.Sprintf("\nat depth %d node %s", depth, spew.Sdump(n))
-		msg += fmt.Sprintf("parent: %s", spew.Sdump(parent))
-		return errors.New(msg)
-	}
-	if flag.gen > parentCachegen {
-		return errorf("cache invariant violation: %d > %d\n", flag.gen, parentCachegen)
-	}
-	if depth > 0 && !parentDirty && flag.dirty {
-		return errorf("cache invariant violation: %d > %d\n", flag.gen, parentCachegen)
-	}
-	for _, child := range children {
-		if err := checkCacheInvariant(child, n, flag.gen, flag.dirty, depth+1); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
 func TestRandom(t *testing.T) {
 	if err := quick.Check(runRandTest, nil); err != nil {
 		if cerr, ok := err.(*quick.CheckError); ok {
@@ -626,6 +556,6 @@ func TestDecodeNode(t *testing.T) {
 	for i := 0; i < 5000000; i++ {
 		rand.Read(hash)
 		rand.Read(elems)
-		decodeNode(hash, elems, 1)
+		decodeNode(hash, elems)
 	}
 }