Live page migration for hybrid memory virtual machines

Abstract

The present invention relates to a hybrid memory system with live page migration for virtual machine, and the system comprises a physical machine installed with a virtual machine and being configured to: build a channel for a shared memory between the virtual machine and a hypervisor; make the hypervisor generate to-be-migrated cold / hot page information and writing write the to-be-migrated cold / hot page information into the shared memory; make the virtual machine read the to-be-migrated cold / hot page information from the shared memory; and make the virtual machine according to the read to-be-migrated cold / hot page information perform a page migration process across heterogeneous memories of the virtual machine without stopping the virtual machine.

Description

FIELD[0001]The present invention relates to hybrid memory system for virtual machines, and more particularly to a hybrid memory system with live page migration for virtual machine.DESCRIPTION OF RELATED ART[0002]With the progress of hardware technology, various non-volatile storage media have been developed in the industrial circles. These storage media have many potential advantages such as low idle energy consumption, high read / write speed, good byte addressability, and high storage density, and are expected to be substitutes of DRAM in large memory systems. Storage class memory (SCM) is an abstract of these novel non-volatile memory devices. The emergence and applications of SCM break the boundary between memory and storage and allow CPUs to directly access data storage in SCM. In addition, due to the non-volatile nature of SCM, there is no need to store calculation results in external storage having the nature of persistent storage, and this effectively addresses data I / O bottle...

AI Technical Summary

Benefits of technology

[0006]In view of the shortcomings of the prior art, the present invention provides a hybrid memory system with live page migration for virtual machine. The present invention performs page migration by means of reserved shared memory and coordination between its virtual machine and hypervisor. The hypervisor generates to-be-migrated cold / hot page information and sends the information to the virtual machine through the shared memory, so that the virtual machine performs a page migration process across heterogeneous memories of the virtual machine without stopping the virtual machine according to the to-be-migrated cold / hot page information, thereby improving page migration in terms of efficiency and effectiveness, while optimizing performance of the hybrid memory of the virtual machine.

[0022]The hybrid memory system with live page migration for virtual machine according to the present invention has at least the following advantages:

[0023]First, the virtual machine can have page migration performed without interrupt of operation. In the prior art, memory page migration is transparent to virtual machines and the whole page migration process is fully controlled by a hypervisor. For integrity and accuracy of data in a virtual machine during migration, the virtual machine has to be hung up during the migration process and resumes its operation after migration. Besides, false positives can appear for page migration. Performing page migration without hanging up the virtual machine can lead to bad data consistency between the physical machine and the virtual machine. This is because the virtual machine cannot “see” the hypervisor when the latter performs page migration, which means if a memory page accessed by the virtual machine has been migrated by the hypervisor, the virtual machine reads wrong data or non-expected data, leading to degraded data consistency and accuracy of the virtual machine. The scheme of the present invention eliminates interrupt costs otherwise required by the virtual machine. The hypervisor scans page tables to acquire cold / hot page information. The virtual machine performs migration and the coordination and cooperation of the both realize memory page migration across NUMA nodes, thereby improving page migration in terms of efficiency and effectiveness, and optimizing overall memory performance of the virtual machine.

[0024]Second, the present invention improves page migration in terms of effectiveness. With the memory region shared by the virtual machine and the hypervisor, information exchange can be achieved between the virtual machine and the hypervisor to optimize scanning of page tables and to prevent degradation of performance caused by false positives that otherwise occur in the traditional page migration operations. By comparison, the disclosed approach based on coordination between the virtual machine and the hypervisor enhances information exchange in implicit memory regions and supports page migration strategies with better performance. The term “false positive” originally refers to a case where a positive result is wrongly determined for a subject that does not have any positive symptoms for some reasons. In the context of page migration, the same term refers to a case where a hypervisor does not know about address information (e.g. anonymous memory, file mapping, cache, stacking, etc.) of progress run in a virtual machine as associated with the traditional page migration schemes. This can lead to invalid page migration in which a memory page determined as a hot page by the hypervisor is actually not frequently accessed after migration. In the disclosed scheme, page migration is performed within the virtual machine, and the virtual machine can refer to the information about the memory regions contained in the progress to further determine the degree of heat or cold of a page, thereby reducing invalid page migration.

[0026]Fourth, the present invention manages cold / hot page information using multi-level hash linked lists, in which linked lists having the lower level has the lower write frequentness and scanning level, thereby reducing useless page scanning.

Problems solved by technology

However, as compared to DRAM, the existing SCM products have imbalance between read speed and write speed thereof, and some of them even have limited write cycles.

A hybrid memory structure based on the traditional DRAM and SCM nevertheless brings about new challenges to the designers of computer system software.

Besides, false positive of page migration is exposed as a problem.

As a result, the overall efficiency of memory page migration is low and the system overhead is high.

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