[ceph-users] pool pgp_num not updated

Hi guys, When I update the pg_num of a pool, I found it not worked(no rebalanced), anyone know the reason? Pool's info: pool 21 'openstack-volumes-rs' replicated size 3 min_size 2 crush_rule 21 object_hash rjenkins pg_num 1024 pgp_num 512 pgp_num_target 1024 autoscale_mode warn last_change 85103 lfor 82044/82044/82044 flags hashpspool,nodelete,selfmanaged_snaps stripe_width 0 application rbd         removed_snaps [1~1e6,1e8~300,4e9~18,502~3f,542~11,554~1a,56f~1d7] pool 22 'openstack-vms-rs' replicated size 3 min_size 2 crush_rule 22 object_hash rjenkins pg_num 512 pgp_num 512 pg_num_target 256 pgp_num_target 256 autoscale_mode warn last_change 84769 lfor 0/0/55294 flags hashpspool,nodelete,selfmanaged_snaps stripe_width 0 application rbd The pgp_num_target is set, but pgp_num not set. I have scale out new OSDs and is backfilling before setting the value, is it the reason?