Memory duplication by origin host in virtual machine live migration

• US 9,454,400 B2
• Filed: 08/16/2013
• Issued: 09/27/2016
• Est. Priority Date: 08/16/2013
• Status: Active Grant

• Current Assignee: Red Hat Israel Ltd. (International Business Machines Corporation)
• Original Assignee: Red Hat Israel Ltd. (International Business Machines Corporation)
• Inventors: Tsirkin, Michael, Noel, Karen
• Primary Examiner(s): Yi, David X
• Assistant Examiner(s): Mercado, Ramon A
• Application Number:
  US13/968,795
• Publication Number:
  US 20150052322A1
• Time in Patent Office: 1,138 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/10 Address translation
• CPC Class Codes: G06F 9/4856 resumption being on a different machine, e.g. task migration, virtual machine migration G06F9/5088 takes precedence

Abstract

Systems and methods for memory de-duplication in a virtual machine undergoing live migration. An example method may comprise: determining a first identifier identifying a first physical memory range, the first physical memory range mapped to a first virtual memory range in a virtual address space of a first virtual machine undergoing live migration from a origin host computer system to a destination host computer system; determining a second identifier identifying a second physical memory range, the second physical memory range mapped to a second virtual memory range in a virtual address space of a second virtual machine undergoing live migration from the origin host computer system to the destination host computer system; determining that the first identifier and the second identifier identify the same physical memory range; and notifying the destination host computer system that the first virtual memory range and the second virtual memory range have identical contents.

Claims

1. A method, comprising:

providing a data structure comprising a plurality of memory mapping entries, each memory mapping entry mapping a virtual memory range to a physical memory range identified by a memory device, a physical address on the memory device, and a reference count of virtual memory ranges mapped to the physical memory range, wherein the data structure only comprises memory mapping entries having the reference count of two or more;

determining, by a processor of an origin host computer system, using the data structure, a first physical address identifying a first physical memory range, the first physical memory range mapped to a first virtual memory range in a virtual address space of a first virtual machine undergoing live migration from the origin host computer system to a destination host computer system;

determining a second physical address identifying a second physical memory range, the second physical memory range mapped to a second virtual memory range in a virtual address space of a second virtual machine undergoing live migration from the origin host computer system to the destination host computer system;

determining, by the processor, that the first physical address and the second physical address are identical; and

notifying the destination host computer system that the first virtual memory range and the second virtual memory range have identical contents.

2. The method of claim 1, further comprising:

indexing the data structure by the memory device and the physical address on the memory device.

3. The method of claim 1, further comprising:

clearing a dirty state of the first virtual memory range, before retrieving from the data structure the first identifier identifying the first physical memory range.

4. The method of claim 1, further comprising:

responsive to notifying the destination host computer system that the first virtual memory range and the second virtual memory range have identical contents, decrementing a corresponding reference count in the memory mapping data structure.

5. A system comprising:

a memory; and

a processor, operatively coupled to the memory, to;

provide a data structure comprising a plurality of memory mapping entries, each memory mapping entry mapping a virtual memory range to a physical memory range identified by a memory device, a physical address on the memory device, and a reference count of virtual memory ranges mapped to the physical memory range, wherein the data structure only comprises memory mapping entries having the reference count of two or more;

determine, by a hypervisor executing on an origin host computer system, using the data structure, a first physical address identifying a first physical memory range, the first physical memory range mapped to a first virtual memory range in a virtual address space of a first virtual machine undergoing live migration from the origin host computer system to a destination host computer system;

determine a second physical address identifying a second physical memory range, the second physical memory range mapped to a second virtual memory range in a virtual address space of a second virtual machine undergoing live migration from the origin host computer system to the destination host computer system;

determine that the first physical address and the second physical address are identical; and

notify the destination host computer system that the first virtual memory range and the second virtual memory range have identical contents.

6. The system of claim 5, wherein the processor is further to:

index the data structure by the memory device and the physical address on the memory device.

7. A computer-readable non-transitory storage medium comprising executable instructions that, when executed by a processor, cause the processor to:

provide a data structure comprising a plurality of memory mapping entries, each memory mapping entry mapping a virtual memory range to a physical memory range identified by a memory device, a physical address on the memory device, and a reference count of virtual memory ranges mapped to the physical memory range, wherein the data structure only comprises memory mapping entries having the reference count of two or more;

determine, by the processor, using the data structure, a first physical address identifying a first physical memory range, the first physical memory range mapped to a first virtual memory range in a virtual address space of a first virtual machine undergoing live migration from an origin host computer system to a destination host computer system;

determine a second physical address identifying a second physical memory range, the second physical memory range mapped to a second virtual memory range in a virtual address space of a second virtual machine undergoing live migration from the origin host computer system to the destination host computer system;

determine, by the processor, that the first physical address and the second physical address are identical; and

notify the destination host computer system that the first virtual memory range and the second virtual memory range have identical contents.

8. The computer-readable non-transitory storage medium of claim 7, further comprising executable instructions causing the processor to index the data structure by the memory device and the physical address on the memory device.

9. The computer-readable non-transitory storage medium of claim 7, executable instructions causing the processor, responsive to notifying the destination host computer system that the first virtual memory range and the second virtual memory range have identical contents, to decrement a corresponding reference count in the memory mapping data structure.