On Tue, May 16, 2023 at 1:37 PM Andrei Elkin wrote:

Can you comment on chances for `flush_lsn` never advance to the value of `write_lsn` when/because Innodb has nothing to commit (so at such a time RM (or PURGE or FLUSH LOGS that have been mentioned too) might be run)?

If the last write to the log was an InnoDB internal one, it could be done by log_write_up_to(lsn, false). The log_sys.flushed_to_disk_lsn would only be advanced (to somewhere closer to log_sys.lsn) if there was a subsequent call to log_write_up_to(lsn, true). Log checkpoint would advance log_sys.flushed_to_disk_lsn, as should a user transaction commit. This could be a possible explanation. -- Marko Mäkelä, Lead Developer InnoDB MariaDB plc