cmd, core, eth, light, trie: add trie read caching layer

core/state/database.go

@@ -72,13 +72,19 @@ type Trie interface {
 }
 
 // NewDatabase creates a backing store for state. The returned database is safe for
-// concurrent use and retains cached trie nodes in memory. The pool is an optional
-// intermediate trie-node memory pool between the low level storage layer and the
-// high level trie abstraction.
+// concurrent use and retains a few recent expanded trie nodes in memory. To keep
+// more historical state in memory, use the NewDatabaseWithCache constructor.
 func NewDatabase(db ethdb.Database) Database {
+	return NewDatabaseWithCache(db, 0)
+}
+
+// NewDatabase creates a backing store for state. The returned database is safe for
+// concurrent use and retains both a few recent expanded trie nodes in memory, as
+// well as a lot of collapsed RLP trie nodes in a large memory cache.
+func NewDatabaseWithCache(db ethdb.Database, cache int) Database {
 	csc, _ := lru.New(codeSizeCacheSize)
 	return &cachingDB{
-		db:            trie.NewDatabase(db),
+		db:            trie.NewDatabaseWithCache(db, cache),
 		codeSizeCache: csc,
 	}
 }