From qemu-kvm-9.0.0, new parameter called "zero-page-detection" is supported, allowing the user to choose the policy for detecting zero pages.

It has three options: 
1) none: not to do zero page detection, this option before RHEL-9.4 can not be selected, It's a better choice under some scenarios if the guest page is not zero-page
2) legacy; do the detection only in the main thread.
3) multifd: the recommended use, zero page detection will be put into multiple threads.
Zero page detection offloading for multifd, so that idle guest migration should get a major boost when multifd is enabled