SQL query takes twice as long on ext4 than it does on ext3

Issue

1. After change filesystem from ext3 to ext4, when perform simple insert/commit test in MySQL, the time is different. Pseudo procedures:

while (i<10000) {
 insert <value> to tables;
 commit;
 i++;
}

On ext4:

mysql> call SampleProc(10000);
Query OK, 0 rows affected (21.59 sec)

On ext3:

mysql> call SampleProc(10000);
Query OK, 0 rows affected (9.87 sec)

2. On some servers, after disabling barrier on ext4, the performance looks better, however, there is no difference between with/without barrier on ext4 on some other servers, why?