Why Completely Fair Scheduler(CFS) using Red-Black tree instead of Min-heap?

Hi, Currently, I am learning about CFS scheduler in linux, and I want to know reason about the data structure chooses in CFS implementation. CFS scheduler picks next process based on minimum virtual time and to get this value efficiently its using Red-Black tree(rbtree), using rbtree we will get minimum O(h) here h is height of rbtree. But, using min-heap we can get min virtual time process in O(1) time only. I just want to know why min-heap is not consider in CFS implementation and is there any difficulties using min-heap in kernel level? Thanks in advance. -- *Regards,* *Venugopal Reddy.*