Description of problem:
There is an issue with slow backfill when mclock_scheduler is used, the osd_mclock_override_recovery_settings=true + osd_max_backfills=8 does not seem to have any effect on amount of PGs being in backfilling state:
---
data:
    volumes: 1/1 healthy
    pools:   42 pools, 10488 pgs
    objects: 710.17M objects, 2.1 PiB
    usage:   5.4 PiB used, 16 PiB / 21 PiB avail
    pgs:     21327554/4573948158 objects misplaced (0.466%)
             10341 active+clean
             68    active+remapped+backfill_wait
             61    active+clean+scrubbing+deep
             14    active+clean+scrubbing
             4     active+remapped+backfilling
 
  io:
    client:   551 MiB/s rd, 23 MiB/s wr, 501 op/s rd, 611 op/s wr
    recovery: 21 MiB/s, 6 objects/s
---
ceph_config_dump:osd                                                                                                         advanced  osd_max_backfills                              8                                                                                                                                    
ceph_config_dump:osd                                                                                                         advanced  osd_mclock_override_recovery_settings          true     
---

The data moved are cephfs data pool EC profile = 8+3, the reason for data movement is to move data from old HDD OSDs to new HDD_ECC OSDs (both with block.db on SSD)

Version-Release number of selected component (if applicable):
RHCS 6.1z6
ceph version 17.2.6-216.el9cp

How reproducible:
Always in this environment

Steps to Reproduce:
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Actual results:


Expected results:


Additional info: