SHARING READ-ONLY DATA AMONG VIRTUAL MACHINES USING COHERENT ACCELERATOR PROCESSOR INTERFACE (CAPI) ENABLED FLASH

• US 20170168736A1
• Filed: 12/10/2015
• Published: 06/15/2017
• Est. Priority Date: 12/10/2015
• Status: Active Application

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Batra, Gaurav, Damodaran, Anil Kumar K., Griffith, Douglas, Sulu, Amarendar N.
• Granted Patent: US 10,261,703 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 2009/45579 I/O management, e.g. providing access to device drivers or storage
• CPC Class Codes: G06F 2009/45583 Memory management, e.g. access or allocation
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0622 in relation to access
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0656 Data buffering arrangements
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G06F 3/0685 Hybrid storage combining heterogeneous device types, e.g. hierarchical storage, hybrid arrays
• CPC Class Codes: G06F 9/45558 Hypervisor-specific management and integration aspects

Abstract

Sharing read-only data among virtual machines (VM) using an attached coherent accelerator processor interface (CAPI) enabled flash storage (CeFS) is provided. The method includes mapping a file, by a virtual machine monitor, from the CeFS into a range of common memory in the virtual machine monitor. The VM shares the mapped file with at least one other VM at a range of common memory in their address spaces. A redirect-on-write filesystem (RoWFS) is created on the VM and the at least one other VM, whereby the RoWFS includes a read-only copy and a private copy of a linear memory map of the mapped file. A data page is read using the copy of the linear memory map, and the data page is modified using the private copy of the linear memory map.

Claims

1. A processor-implemented method for sharing read-only data among virtual machines (VM) using an attached coherent accelerator processor interface (CAPI) enabled flash storage (CeFS), comprising:

mapping a file, by a virtual machine monitor, from the CeFS into a range of common memory in the virtual machine monitor;

including the range of common memory in the VM internal address space, wherein the VM shares the mapped file with at least one other VM;

creating a redirect-on-write filesystem (RoWFS) on the VM and the at least one other VM, wherein the RoWFS includes a read-only copy and a private copy of a linear memory map of the mapped file; and

reading a data page using the copy of the linear memory map, and modifying the data page using the private copy of the linear memory map.

2. The method of claim 1, further comprising:

in response to receiving a request to read the data page from the mapped file, the RoWFS searching for the requested data page using the private copy of the linear memory map;

retrieving the requested data page from the VM writeable private area (VMWPA) based on the requested data page being previously modified; and

retrieving the requested data page from the mapped file using the read-only copy of the linear memory map based on the requested data page not being previously modified.

3. The method of claim 1, further comprising:

in response to receiving the request to modify data page from the mapped file, the RoWFS searching for the requested data page using the private copy of the linear memory map and the read-only copy of the common linear map;

retrieving the requested data page into cache memory of the VM from the VMWPA or the mapped file;

modifying the retrieved data page and updating the private copy of the linear memory map; and

flushing the modified data page and the updated private copy of the linear memory map to the VMPA.

4. The method of claim 1, wherein the RoWFS includes the read-only copy and the private copy of the linear memory map, and the VMWPA, wherein the VMWPA includes a dedicated tangible storage device.

5. The method of claim 1, wherein each participating VM shares one read-only copy of the memory mapped file, one read-only copy of the linear memory map, and wherein each participating VM has a dedicated private copy of the linear memory map and a dedicated private copy of the data page modified by the participating VM.

6. The method of claim 1, wherein the memory mapped file is created in the range of common memory in the virtual machine monitor and wherein the range of common memory is exposed into one or more address spaces of VMs sharing the memory mapped file.

7. The method of claim 3, wherein the requested data page is retrieved from the VMWPA based on the requested data page being located using the private copy of the linear memory map, and wherein the requested data page is retrieved from the mapped file based on the requested data page being located using the read-only copy of the linear memory map of the mapped file.

8. A computer program product for sharing read-only data among virtual machines (VM) using an attached coherent accelerator processor interface (CAPI) enabled flash storage (CeFS), comprising:

a redirect-on-write filesystem (RoWFS) of a computer operating system embodied on a computer readable storage medium, the RoWFS including program instructions executable by a processor, the program instructions comprising;

program instructions to map a file, by a virtual machine monitor, from the CeFS into a range of common memory in the virtual machine monitor;

program instructions to include the range of common memory in the VM internal address space, wherein the VM shares the mapped file with at least one other VM;

program instructions to create a redirect-on-write filesystem (RoWFS) on the VM and the at least one other VM, wherein the RoWFS includes a read-only copy and a private copy of a linear memory map of the mapped file; and

program instructions to read a data page using the copy of the linear memory map, and modifying the data page using the private copy of the linear memory map.

9. The computer program product of claim 8, further comprising:

in response to program instructions to receive a request to read the data page from the mapped file, the RoWFS searching for the requested data page using the private copy of the linear memory map;

program instructions to retrieve the requested data page from the VM writeable private area (VMWPA) based on the requested data page being previously modified; and

program instructions to retrieve the requested data page from the mapped file using the read-only copy of the linear memory map based on the requested data page not being previously modified.

10. The computer program product of claim 8, further comprising:

in response to program instructions to receive the request to modify data page from the mapped file, the RoWFS searching for the requested data page using the private copy of the linear memory map and the read-only copy of the common linear map;

program instructions to retrieve the requested data page into cache memory of the VM from the VMWPA or the mapped file;

program instructions to modify the retrieved data page and updating the private copy of the linear memory map; and

program instructions to flush the modified data page and the updated private copy of the linear memory map to the VMPA.

11. The computer program product of claim 8, wherein the RoWFS includes the read-only copy and the private copy of the linear memory map, and the VMWPA, wherein the VMWPA includes a dedicated tangible storage device.

12. The computer program product of claim 8, wherein each participating VM shares one read-only copy of the memory mapped file, one read-only copy of the linear memory map, and wherein each participating VM has a dedicated private copy of the linear memory map and a dedicated private copy of the data page modified by the participating VM.

13. The computer program product of claim 8, wherein the memory mapped file is created in the range of common memory in the virtual machine monitor and wherein the range of common memory is exposed into one or more address spaces of VMs sharing the memory mapped file.

14. The computer program product of claim 10, wherein the requested data page is retrieved from the VMWPA based on the requested data page being located using the private copy of the linear memory map, and wherein the requested data page is retrieved from the mapped file based on the requested data page being located using the read-only copy of the linear memory map of the mapped file.

15. A computer system for sharing read-only data among virtual machines (VM) using an attached coherent accelerator processor interface (CAPI) enabled flash storage (CeFS), comprising:

one or more processors, one or more computer-readable storage devices, and a plurality of program instructions stored on at least one of the one or more storage devices for execution by at least one of the one or more processors, the plurality of program instructions comprising;

program instructions to map a file, by a virtual machine monitor, from the CeFS into a range of common memory in the virtual machine monitor;

program instructions to include the range of common memory in the VM internal address space, wherein the VM shares the mapped file with at least one other VM;

program instructions to create a redirect-on-write filesystem (RoWFS) on the VM and the at least one other VM, wherein the RoWFS includes a read-only copy and a private copy of a linear memory map of the mapped file; and

program instructions to read a data page using the copy of the linear memory map, and modifying the data page using the private copy of the linear memory map.

16. The computer system of claim 15, further comprising:

in response to program instructions to receive a request to read the data page from the mapped file, the RoWFS searching for the requested data page using the private copy of the linear memory map;

program instructions to retrieve the requested data page from the VM writeable private area (VMWPA) based on the requested data page being previously modified; and

program instructions to retrieve the requested data page from the mapped file using the read-only copy of the linear memory map based on the requested data page not being previously modified.

17. The computer system of claim 15, wherein the RoWFS includes the read-only copy and the private copy of the linear memory map, and the VMWPA, wherein the VMWPA includes a dedicated tangible storage device.

18. The computer system of claim 15, wherein the memory mapped file is created in the range of common memory in the virtual machine monitor and wherein the range of common memory is exposed into one or more address spaces of VMs sharing the memory mapped file.

19. The computer system of claim 15, further comprising:

in response to program instructions to receive the request to modify data page from the mapped file, the RoWFS searching for the requested data page using the private copy of the linear memory map and the read-only copy of the common linear map;

program instructions to retrieve the requested data page into cache memory of the VM from the VMWPA or the mapped file;

program instructions to modify the retrieved data page and updating the private copy of the linear memory map; and

program instructions to flush the modified data page and the updated private copy of the linear memory map to the VMPA.

20. The computer system product of claim 17, wherein the requested data page is retrieved from the VMWPA based on the requested data page being located using the private copy of the linear memory map, and wherein the requested data page is retrieved from the mapped file based on the requested data page being located using the read-only copy of the linear memory map of the mapped file.