Ceph » rbd

For example, there are two IO's, IO1 and IO2, and IO1 enters the IO queue before IO2.

If the following conditions are met:
1. When io1 enters qos, there are not enough tokens and io1 enters qos queue.
2. If io1 obtains enough tokens, IO1 is placed after IO2.
2. When there are enough tokens for IO2, IO2 dequeues.
3. Because IO1 has acquired the token, it directly dequeued.

In this case, IO2 is processed before IO1, resulting in out-of-order processing.