A virtualized computer system implements a process to migrate a virtual machine (VM) from a source host to a destination host. During this process, a processing unit at the source host, which is executing instructions of the VM, is scheduled so that the rate of modification of guest physical memory pages is reduced. The determination of when to schedule the processing unit in this manner may be made based on a current rate of modification of the pages, a transmission rate of guest physical memory pages from the source host to the destination host, or a prior VM migration performance.