cmd/geth, trie: track and report trie cache misses

trie/trie.go

@@ -20,6 +20,7 @@ package trie
 import (
 	"bytes"
 	"fmt"
+	"sync/atomic"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto/sha3"
@@ -34,6 +35,17 @@ var (
 	emptyState common.Hash
 )
 
+// cacheMisses maintains the number of times a trie node was loaded from disk.
+// Always use atomic operations when accessing this global variable.
+var cacheMisses uint64
+
+// CacheMisses retrieves a global counter measuring the number of cache misses
+// the trie did since process startup. This isn't useful for anything apart from
+// trie debugging purposes.
+func CacheMisses() uint64 {
+	return atomic.LoadUint64(&cacheMisses)
+}
+
 func init() {
 	sha3.NewKeccak256().Sum(emptyState[:0])
 }
@@ -419,6 +431,8 @@ func (t *Trie) resolve(n node, prefix, suffix []byte) (node, error) {
 }
 
 func (t *Trie) resolveHash(n hashNode, prefix, suffix []byte) (node, error) {
+	atomic.AddUint64(&cacheMisses, 1)
+
 	enc, err := t.db.Get(n)
 	if err != nil || enc == nil {
 		return nil, &MissingNodeError{