How many logs can journal log driver handle in one second?

Hi, all
I have used journald as the log driver.
But I saw only about 700 messages per second could be displayed (using ‘docker log’ command) , no matter how many logs are printed in one second.

Does anyone know why?
Does journald only handle 700 messages per second?
Or there is something I need to tune?

Thanks.

Best regards.