I am trying to import a database into a slave server. The process is being slowed because mysql calls fsync at a crazy rate. The jbd2/dm-0-8 runs at 80 - 99 % continuously but the throughput is quite low. It was running at a few kb/s till I implemented the following changes
innodb_flush_sync = OFF sync_binlog= 0 sync_frm = ON sync_master_info = 0 sync_relay_log = 10000 sync_relay_log_info = 0 innodb_flush_log_at_trx_commit = 0
It's now running at about 12Mb/s. I'm sure if I can do something further to decrease fsync calls it will help this.