diff --git a/util/chunk/iterator.go b/util/chunk/iterator.go
index 63aabde256c5d..74d78b9cb62ea 100644
--- a/util/chunk/iterator.go
+++ b/util/chunk/iterator.go
@@ -14,6 +14,8 @@
 
 package chunk
 
+import "golang.org/x/sys/cpu"
+
 var (
 	_ Iterator = (*Iterator4Chunk)(nil)
 	_ Iterator = (*iterator4RowPtr)(nil)
@@ -58,8 +60,10 @@ func NewIterator4Slice(rows []Row) Iterator {
 
 // Iterator4Slice is used to iterate rows inside a slice.
 type Iterator4Slice struct {
+	_      cpu.CacheLinePad
 	rows   []Row
 	cursor int
+	_      cpu.CacheLinePad
 }
 
 // Begin implements the Iterator interface.