diff --git a/model/query_piece.go b/model/query_piece.go
index 6493899..c0375de 100644
--- a/model/query_piece.go
+++ b/model/query_piece.go
@@ -34,7 +34,7 @@ const (
 
 var (
 	mqpp                 = NewMysqlQueryPiecePool()
-	localSliceBufferPool = NewSliceBufferPool("json cache", 1*1024*1024)
+	localSliceBufferPool = NewSliceBufferPool("json cache", 256*1024)
 )
 
 var commonBaseQueryPiece = &BaseQueryPiece{}
diff --git a/session-dealer/mysql/const.go b/session-dealer/mysql/const.go
index 0691258..adc4780 100644
--- a/session-dealer/mysql/const.go
+++ b/session-dealer/mysql/const.go
@@ -93,10 +93,9 @@ const (
 
 
 // Identifier length limitations.
-// See https://dev.mysql.com/doc/refman/5.7/en/identifiers.html
 const (
 	// MaxMysqlPacketLen is the max packet payload length.
-	MaxMysqlPacketLen = 512 * 1024
+	MaxMysqlPacketLen = 128 * 1024
 )
 
 const (