When the file system is dealing with multithreading concurrent writing to a file,
the performance will be degraded because of the lock.
At present, the default AIO mode of QEMU NBD is threads. In the case of large blocks,
because IO is divided into small pieces and multiple queues, it will become multithreading
concurrent writing the same file. Due to the file system, the performance will be greatly reduced.
If you change to native mode, this problem will not exist.
Signed-off-by: wangjian161 <wangjian161@huawei.com>
