Content-Based Swap Candidate Selection

• US 20150301843A1
• Filed: 04/16/2014
• Published: 10/22/2015
• Est. Priority Date: 04/16/2014
• Status: Active Grant

• Current Assignee: Vmware LLC (Broadcom, Inc.)
• Original Assignee: VMware, Inc. (Broadcom, Inc.)
• Inventors: Guo, Fei, Yedlapalli, Praveen
• Granted Patent: US 9,342,344 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/08 in hierarchically structured memory systems, e.g. virtual memory systems
• CPC Class Codes: G06F 2009/45583 Memory management, e.g. access or allocation
• CPC Class Codes: G06F 2212/152 Virtualized environment, e.g. logically partitioned system
• CPC Class Codes: G06F 2212/401 Compressed data
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects
• CPC Class Codes: G06F 9/5016 the resource being the memory

Abstract

Techniques for building a list of swap candidate pages for host swapping are provided. In one embodiment, a host system can determine a swap target virtual machine (VM) and a target number of swap candidate pages. The host system can further select a memory page from a memory space of the swap target VM and can check whether the memory page is sharable or compressible. If the memory page is sharable or compressible, the host system can add the memory page to the list of swap candidate pages.

Claims

1. A method for building a list of swap candidate pages for host swapping, the method comprising:

determining, by a host system, a swap target virtual machine (VM) and a target number of swap candidate pages;

selecting, by the host system, a memory page from a memory space of the swap target VM;

checking, by the host system, whether the memory page is sharable or compressible; and

adding, by the host system, the memory page to the list of swap candidate pages if the memory page is sharable or compressible.

2. The method of claim 1 wherein the memory page is sharable if a sharability bit is set within a metadata portion of the memory page.

3. The method of claim 1 wherein the memory page is compressible if the memory page can be compressed to an output compression ratio that satisfies a predetermined target compression ratio.

4. The method of claim 1 wherein the memory page is selected at random from the memory space of the swap target VM, and wherein the selecting, the checking and the adding are repeated until:

a number of memory pages added to the list of swap candidate pages reaches the target number;

or

a number of memory pages selected at random from the memory space of the swap target VM reaches a first limit value.

5. The method of claim 4 wherein the first limit value is a multiple of the target number.

6. The method of claim 4 wherein, if the number of memory pages selected at random from the memory space of the swap target VM reaches the first limit value before the number of memory pages added to the list of swap candidate pages reaches the target number, the method further comprises:

selecting a memory page sequentially from the memory space of the swap target VM;

checking whether the memory page is sharable or compressible; and

adding the memory page to the list of swap candidate pages if the memory page is sharable or compressible,

wherein the selecting, the checking, and the adding are repeated until;

the number of memory pages added to the list of swap candidate pages reaches the target number;

or

a number of memory pages selected sequentially from the memory space of the swap target VM reaches a second limit value.

7. The method of claim 5 wherein, if the number of memory pages selected at sequentially from the memory space of the swap target VM reaches the second limit value before the number of memory pages added to the list of swap candidate pages reaches the target number, the method further comprises:

adding additional memory pages from the memory space of the swap target VM to the list of swap candidate pages, without checking whether the additional memory pages are sharable or compressible, until the number of memory pages added to the list of swap candidate pages reaches the target number.

8. A non-transitory computer readable storage medium having stored thereon software executable by a host system, the software embodying a method for building a list of swap candidate pages for host swapping, the method comprising:

determining a swap target VM and a target number of swap candidate pages;

selecting a memory page from a memory space of the swap target VM;

checking whether the memory page is sharable or compressible; and

adding the memory page to the list of swap candidate pages if the memory page is sharable or compressible.

9. The non-transitory computer readable storage medium of claim 8 wherein the memory page is sharable if a sharability bit is set within a metadata portion of the memory page.

10. The non-transitory computer readable storage medium of claim 8 wherein the memory page is compressible if the memory page can be compressed to an output compression ratio that satisfies a predetermined target compression ratio.

11. The non-transitory computer readable storage medium of claim 8 wherein the memory page is selected at random from the memory space of the swap target VM, and wherein the selecting, the checking and the adding are repeated until:

a number of memory pages added to the list of swap candidate pages reaches the target number;

or

a number of memory pages selected at random from the memory space of the swap target VM reaches a first limit value.

12. The non-transitory computer readable storage medium of claim 11 wherein the first limit value is a multiple of the target number.

13. The non-transitory computer readable storage medium of claim 11 wherein, if the number of memory pages selected at random from the memory space of the swap target VM reaches the first limit value before the number of memory pages added to the list of swap candidate pages reaches the target number, the method further comprises:

selecting a memory page sequentially from the memory space of the swap target VM;

checking whether the memory page is sharable or compressible; and

adding the memory page to the list of swap candidate pages if the memory page is sharable or compressible,

wherein the selecting, the checking, and the adding are repeated until;

the number of memory pages added to the list of swap candidate pages reaches the target number;

or

a number of memory pages selected sequentially from the memory space of the swap target VM reaches a second limit value.

14. The non-transitory computer readable storage medium of claim 13 wherein, if the number of memory pages selected at sequentially from the memory space of the swap target VM reaches the second limit value before the number of memory pages added to the list of swap candidate pages reaches the target number, the method further comprises:

adding additional memory pages from the memory space of the swap target VM to the list of swap candidate pages, without checking whether the additional memory pages are sharable or compressible, until the number of memory pages added to the list of swap candidate pages reaches the target number.

15. A computer system comprising:

a processor; and

a non-transitory computer readable medium having stored thereon program code that causes the processor to, upon being executed;

determine a swap target VM and a target number of swap candidate pages;

select a memory page from a memory space of the swap target VM;

check whether the memory page is sharable or compressible; and

add the memory page to a list of swap candidate pages if the memory page is sharable or compressible.

16. The computer system of claim 15 wherein the memory page is sharable if a sharability bit is set within a metadata portion of the memory page.

17. The computer system of claim 15 wherein the memory page is compressible if the memory page can be compressed to an output compression ratio that satisfies a predetermined target compression ratio.

18. The computer system of claim 15 wherein the memory page is selected at random from the memory space of the swap target VM, and wherein the selecting, the checking and the adding are repeated until:

a number of memory pages added to the list of swap candidate pages reaches the target number;

or

a number of memory pages selected at random from the memory space of the swap target VM reaches a first limit value.

19. The computer system of claim 18 wherein the first limit value is a multiple of the target number.

20. The computer system of claim 18 wherein, if the number of memory pages selected at random from the memory space of the swap target VM reaches the first limit value before the number of memory pages added to the list of swap candidate pages reaches the target number, the program code further causes the processor to:

select a memory page sequentially from the memory space of the swap target VM;

check whether the memory page is sharable or compressible; and

add the memory page to the list of swap candidate pages if the memory page is sharable or compressible,

wherein the selecting, the checking, and the adding are repeated until;

the number of memory pages added to the list of swap candidate pages reaches the target number;

or

a number of memory pages selected sequentially from the memory space of the swap target VM reaches a second limit value.

21. The computer system of claim 20 wherein, if the number of memory pages selected at sequentially from the memory space of the swap target VM reaches the second limit value before the number of memory pages added to the list of swap candidate pages reaches the target number, the program code further causes the processor to:

add additional memory pages from the memory space of the swap target VM to the list of swap candidate pages, without checking whether the additional memory pages are sharable or compressible, until the number of memory pages added to the list of swap candidate pages reaches the target number.