After more than 4 years of development, mclock is the default scheduler for ceph quincy (version 17).If you don't want to use the scheduler, you can disable it with the option osd_op_queue.
WPQ was the default before Ceph Quincy and the change requires a restart of the OSDs.
Source:
https://docs.ceph.com/en/quincy/rados/configuration/osd-config-ref/#confval-osd_op_queue"
https://docs.ceph.com/en/quincy/rados/configuration/osd-config-ref/#qos-based-on-mclock>"