Online classification of memory pages based on activity level represented by one or more bits

摘要

Activity level of memory pages is classified in virtual machine environment, so that processes such as live VM migration and checkpointing, among others, can be carried out more efficiently. The method includes the steps of scanning page table entries of hypervisor-managed page tables continuously over repeating scan periods to determine whether memory pages have been accessed or not, and for each memory page, determining an activity level of the memory page based on whether the memory page has been accessed or not since a prior scan and storing the activity level of the memory page. The activity level of the memory page may be represented by one or more bits of its page table entry and may be classified as having at least two states ranging from hot to cold.

主权项

1. A method of classifying an activity level of memory pages that are accessed by one or more virtual machines executing in a host machine, comprising:
setting a scan rate that defines how frequently page table entries of hypervisor-managed page tables corresponding to the memory pages are to be scanned; scanning the page table entries over multiple scan periods at the scan rate, wherein the page table entries are scanned once during a scan period; and for each of the memory pages and at each scan period in the multiple scan periods, determining an activity level of the memory page using a finite state machine that includes a plurality of states, wherein, at each scan period, the finite state machine determines access information for the memory page at each scan period based on whether the memory page has been accessed since a prior scan period, the memory page being determined to have been accessed according to a setting of an accessed or dirty bit of the scanned page table entry of the memory page, and determines a state transition for the memory page to another state based on a current state of the memory page and the access information for the memory page as determined for each scan period; and storing the activity level of the memory page.