core, eth, trie: expose more detailed dirty ram tracking for diff layers (#27971)

core/state/snapshot/snapshot.go

@@ -852,3 +852,21 @@ func (t *Tree) DiskRoot() common.Hash {
 
 	return t.diskRoot()
 }
+
+// Size returns the memory usage of the diff layers above the disk layer and the
+// dirty nodes buffered in the disk layer. Currently, the implementation uses a
+// special diff layer (the first) as an aggregator simulating a dirty buffer, so
+// the second return will always be 0. However, this will be made consistent with
+// the pathdb, which will require a second return.
+func (t *Tree) Size() (diffs common.StorageSize, buf common.StorageSize) {
+	t.lock.RLock()
+	defer t.lock.RUnlock()
+
+	var size common.StorageSize
+	for _, layer := range t.layers {
+		if layer, ok := layer.(*diffLayer); ok {
+			size += common.StorageSize(layer.memory)
+		}
+	}
+	return size, 0
+}