Abstract: In order to reduce the dynamic migration time of virtual machine,the pre-copy algorithm was used in Xen virtual to choose the right time for downtime copy to guarantee the superior performance of virtual machine’s migration in low load or empty load．But with heavy load,Pre-copy algorithm needs to iterative repeatly to the memory pages,which affects processing performance seriously．With algorithm of Xen virtual machine iterative copies,we proposed a mechanism of fragments interative copies to reduce virtual machine live migration time by cutting the termination of time to iterative copy．The results of experiment show that mechanism of memory fragment iteration enhances performance of the live migration of Xen virtual machine.

Key words: Dynamic migration,Virtual machine,Pre-Copy algorithm,Fragments interative copies,Migration time