KSM doesn't merge duplicated data on multi-node NUMA systems

What were you trying to do that didn't work?
KSM is only merging a small portion of duplicated data, allocated at the same time with several workers in the VM. It's important to say that this only happens in RHEL 9 (at least the last three releases) and when the system has more than one NUMA node. It's not depending in the amount of memory the system has and THP is being disabled during the test execution.

Please provide the package NVR for which bug is seen:
Any RHEL 9, at least from the last three minors, e.g. RHEL 9.5
Any QEMU version, e.g. qemu-kvm-8.2.0-6.el9

How reproducible:
100%

Steps to reproduce
1. Run any ksm_overcommit avocado test in a RHEL 9 host with more than one NUMA node.
2. python3 ConfigTest.py --guestname=RHEL.9.5.0 --testcase=ksm_overcommit.ksm_parallel
3. Check the case failed because only a portion of the data has been merged

Expected results
KSM to deduplicate almost all the memory.

Actual results
KSM is only merging a fraction, not enough, of the total duplicated memory.