Auto-commit memory metadata and resetting the metadata by writing to special address in free space of page storing the metadata

• US 9,772,938 B2
• Filed: 09/30/2013
• Issued: 09/26/2017
• Est. Priority Date: 12/13/2010
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Inventors: Talagala, Nisha, Flynn, David
• Primary Examiner(s): Tsui, Daniel
• Assistant Examiner(s): Yew, Chie
• Application Number:
  US14/042,189
• Publication Number:
  US 20140025877A1
• Time in Patent Office: 1,457 Days
• Field of Search: None
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0804 with main memory updating G06F12/0806 takes precedence
• CPC Class Codes: G06F 13/28 using burst mode transfer, e.g. direct memory access DMA, cycle steal G06F13/32 takes precedence
• CPC Class Codes: G06F 2212/202 Non-volatile memory
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• 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]

Abstract

Apparatuses, systems, methods, and computer program products are disclosed. A method includes tracking which portions of data stored in a volatile memory buffer are not yet stored in a non-volatile memory medium. A volatile memory buffer may be accessible using memory semantics. A volatile memory buffer may be associated with logic configured to ensure that the data stored in the volatile memory buffer is non-volatile. A method includes maintaining consistency of data between a volatile memory buffer and a non-volatile memory medium based on tracked portions of the data. A method includes copying at least portions of data not yet stored in a non-volatile memory medium to the non-volatile memory medium in response to a trigger.

Claims

1. A method comprising:

tracking which portions of data stored in a volatile memory buffer are not yet stored in a non-volatile memory medium, the volatile memory buffer associated with hardware configured to ensure that the data stored in the volatile memory buffer becomes stored in the non-volatile memory medium;

maintaining consistency of the data between the volatile memory buffer and the non-volatile memory medium based on the tracked portions of the data;

in response to a trigger, copying at least the portions of the data not yet stored in the non-volatile memory medium to the non-volatile memory medium;

providing metadata indicating which other portions of the data are stored in the non-volatile memory medium, the metadata comprising a bitmask of a first page, the first page comprises a number of bytes, the bitmask comprising a set of bits stored within one eighth of a size of a second page, such that the number of bytes of the first page are represented by the set of bits of the bitmask, the set of bits of the bitmask indicating whether the number of bytes of the first page are stored in the non-volatile memory medium;

providing a clear-all byte at a special address of a host address space for clearing the entire bitmask at once, wherein the special address is located within free space of the second page; and

in response to writing to the clear-all byte, resetting the bitmask.

2. The method of claim 1, further comprising allowing a user to perform write operations for both the bitmask and the first page.

3. The method of claim 1, wherein providing the metadata comprises mapping the metadata and the volatile memory buffer into the host address space.

4. The method of claim 1, wherein the trigger comprises a non-restart event.

5. The method of claim 4, wherein the non-restart event comprises a destage request from a client to copy at least the portions of the data not yet stored in the non-volatile memory medium to the non-volatile memory medium.

6. The method of claim 1, further comprising merging the portions of the data not yet stored in the non-volatile memory medium with one or more previous versions of the data already stored in the non-volatile memory medium.

7. The method of claim 1, further comprising extending a file length for the data in response to at least one of the portions of the data not yet stored in the non-volatile memory medium being associated with an offset beyond a current file length.

8. The method of claim 1, further comprising populating an application-specific persistent object with the data based on application metadata for the data.

9. An apparatus comprising:

a memory module configured to preserve data in a volatile memory to a non-volatile storage medium of a non-volatile storage device in response to a trigger;

a has-been-written module configured to maintain metadata indicating which of the data in the volatile memory is stored in the non-volatile storage medium, the metadata comprising a bitmask of a first page, the first page comprises a number of bytes, the bitmask comprising a set of bits stored within one eighth of a size of a second page, such that the number of bytes of the first page are represented by the set of bits of the bitmask, the set of bits of the bitmask indicating whether the number of bytes of the first page are stored in the non-volatile storage medium, wherein the has-been-written module is configured to provide a clear-all byte at a special address of a host address space for clearing the entire bitmask at once, the special address located within free space of the second page, and to reset the bitmask in response to writing to the clear-all byte; and

a destage module configured to transfer only portions of the data not stored in the non-volatile storage medium from the volatile memory to the non-volatile storage medium based on the maintained metadata.

10. The apparatus of claim 9, wherein the has-been-written module is configured to persist the metadata to the non-volatile storage medium in response to the trigger and to merge the portions of the data not stored in the non-volatile memory transferred by the destage module with one or more previous versions of the data based on the persisted metadata in response to recovery from the trigger, the trigger comprising a restart event.

11. The apparatus of claim 9, wherein the metadata comprises a data structure populated with indicators of which data from the volatile memory has been updated.

12. A method comprising:

maintaining metadata for data of a volatile memory of a storage device, the metadata and the data of the volatile memory mapped into a virtual address space for an application executing on a host computing device coupled to the storage device, the volatile memory associated with a non-volatile storage medium of the storage device, the metadata comprising a bitmask of a first page, the first page comprises a number of bytes, the bitmask comprising a set of bits stored within one eighth of a size of a second page, such that the number of bytes of the first page are represented by the set of bits of the bitmask, the set of bits of the bitmask indicating whether the number of bytes of the first page are stored in the non-volatile storage medium;

providing a clear-all byte at a special address of the virtual address space, for clearing all the metadata at once in response to the application writing to the clear-all byte, wherein the special address is located within free space of the second page;

in response to a trigger, storing the data of the volatile memory and the metadata on the non-volatile storage medium; and

providing the data of the volatile memory and the metadata from the non-volatile storage medium to the application for processing.

13. The method of claim 12, wherein providing the data of the volatile memory from the non-volatile storage medium to the application is in response to recovery from the trigger, the trigger comprising a restart event.

14. The method of claim 12, wherein the metadata comprises one or more of a predefined location for writing the data after the trigger, security data for authenticating a recipient of the data, an identifier of an agent for processing the data, computer executable code for processing the data, a persistent unique identifier for the data, and a location of the data on the non-volatile storage medium.

15. The method of claim 12, wherein:

the metadata identifies an application-specific persistent object; and

providing the data to the application comprises populating the application-specific persistent object with the data in response to recovery from the trigger, the trigger comprising a restart event.

16. The method of claim 15, wherein the application-specific persistent object comprises a database record.