I'm seeing a lot of WALWriteLocks , is this a bad sign , what might cause this?
Are you having a performance problem you are trying to track down? If so, this probably indicates the cause. If not, then it is probably not a bad sign.
The likely cause is that multiple sessions are trying to COMMIT at the same time, and are blocking on the slow fsync of the WAL data. One process will block on WALSync, all the ones queued up behind it will block on WALWrite.