You can also add journal_async_commit,noauto_da_alloc > maybe disable flushes with https://github.com/stewartsmith/libeatmydata https://github.com/stewartsmit

You can also add journal_async_commit,noauto_da_alloc > maybe disable flushes with https://github.com/stewartsmith/libeatmydata https://github.com/stewartsmith/libeatmydata overlayfs has a volatile mount option that has that effect. So stacking a volatile overlayfs with the upper and lower on the same ext4 could provide that behavior even for applications that can't be intercepted with LD_PRELOAD