From 55599ee95d4151a2502465e0afc7c47bd1acba77 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Mon, 5 Feb 2018 18:40:32 +0200
Subject: core, trie: intermediate mempool between trie and database (#15857)

This commit reduces database I/O by not writing every state trie to disk.
---
 trie/hasher.go | 61 +++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 50 insertions(+), 11 deletions(-)

(limited to 'trie/hasher.go')

diff --git a/trie/hasher.go b/trie/hasher.go
index 4719aabf6..2fc44787a 100644
--- a/trie/hasher.go
+++ b/trie/hasher.go
@@ -27,21 +27,23 @@ import (
 )
 
 type hasher struct {
-	tmp                  *bytes.Buffer
-	sha                  hash.Hash
-	cachegen, cachelimit uint16
+	tmp        *bytes.Buffer
+	sha        hash.Hash
+	cachegen   uint16
+	cachelimit uint16
+	onleaf     LeafCallback
 }
 
-// hashers live in a global pool.
+// hashers live in a global db.
 var hasherPool = sync.Pool{
 	New: func() interface{} {
 		return &hasher{tmp: new(bytes.Buffer), sha: sha3.NewKeccak256()}
 	},
 }
 
-func newHasher(cachegen, cachelimit uint16) *hasher {
+func newHasher(cachegen, cachelimit uint16, onleaf LeafCallback) *hasher {
 	h := hasherPool.Get().(*hasher)
-	h.cachegen, h.cachelimit = cachegen, cachelimit
+	h.cachegen, h.cachelimit, h.onleaf = cachegen, cachelimit, onleaf
 	return h
 }
 
@@ -51,7 +53,7 @@ func returnHasherToPool(h *hasher) {
 
 // hash collapses a node down into a hash node, also returning a copy of the
 // original node initialized with the computed hash to replace the original one.
-func (h *hasher) hash(n node, db DatabaseWriter, force bool) (node, node, error) {
+func (h *hasher) hash(n node, db *Database, force bool) (node, node, error) {
 	// If we're not storing the node, just hashing, use available cached data
 	if hash, dirty := n.cache(); hash != nil {
 		if db == nil {
@@ -98,7 +100,7 @@ func (h *hasher) hash(n node, db DatabaseWriter, force bool) (node, node, error)
 // hashChildren replaces the children of a node with their hashes if the encoded
 // size of the child is larger than a hash, returning the collapsed node as well
 // as a replacement for the original node with the child hashes cached in.
-func (h *hasher) hashChildren(original node, db DatabaseWriter) (node, node, error) {
+func (h *hasher) hashChildren(original node, db *Database) (node, node, error) {
 	var err error
 
 	switch n := original.(type) {
@@ -145,7 +147,10 @@ func (h *hasher) hashChildren(original node, db DatabaseWriter) (node, node, err
 	}
 }
 
-func (h *hasher) store(n node, db DatabaseWriter, force bool) (node, error) {
+// store hashes the node n and if we have a storage layer specified, it writes
+// the key/value pair to it and tracks any node->child references as well as any
+// node->external trie references.
+func (h *hasher) store(n node, db *Database, force bool) (node, error) {
 	// Don't store hashes or empty nodes.
 	if _, isHash := n.(hashNode); n == nil || isHash {
 		return n, nil
@@ -155,7 +160,6 @@ func (h *hasher) store(n node, db DatabaseWriter, force bool) (node, error) {
 	if err := rlp.Encode(h.tmp, n); err != nil {
 		panic("encode error: " + err.Error())
 	}
-
 	if h.tmp.Len() < 32 && !force {
 		return n, nil // Nodes smaller than 32 bytes are stored inside their parent
 	}
@@ -167,7 +171,42 @@ func (h *hasher) store(n node, db DatabaseWriter, force bool) (node, error) {
 		hash = hashNode(h.sha.Sum(nil))
 	}
 	if db != nil {
-		return hash, db.Put(hash, h.tmp.Bytes())
+		// We are pooling the trie nodes into an intermediate memory cache
+		db.lock.Lock()
+
+		hash := common.BytesToHash(hash)
+		db.insert(hash, h.tmp.Bytes())
+
+		// Track all direct parent->child node references
+		switch n := n.(type) {
+		case *shortNode:
+			if child, ok := n.Val.(hashNode); ok {
+				db.reference(common.BytesToHash(child), hash)
+			}
+		case *fullNode:
+			for i := 0; i < 16; i++ {
+				if child, ok := n.Children[i].(hashNode); ok {
+					db.reference(common.BytesToHash(child), hash)
+				}
+			}
+		}
+		db.lock.Unlock()
+
+		// Track external references from account->storage trie
+		if h.onleaf != nil {
+			switch n := n.(type) {
+			case *shortNode:
+				if child, ok := n.Val.(valueNode); ok {
+					h.onleaf(child, hash)
+				}
+			case *fullNode:
+				for i := 0; i < 16; i++ {
+					if child, ok := n.Children[i].(valueNode); ok {
+						h.onleaf(child, hash)
+					}
+				}
+			}
+		}
 	}
 	return hash, nil
 }
-- 
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