Monitoring entropic conditions of a flash memory device as an indicator for invoking erasure operations

• US 6,621,746 B1
• Filed: 02/27/2002
• Issued: 09/16/2003
• Est. Priority Date: 02/27/2002
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Aasheim, Jered Donald, Yang, Yongqi
• Primary Examiner(s): Dinh, Son T.
• Application Number:
  US10/087,097
• Publication Number:
  US 20030161186A1
• Time in Patent Office: 566 Days
• Field of Search: 365/185.29, 365/185.33, 365/218, 365/230.03, 711/103
• US Class Current: 365/185.29
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G11C 16/16 for erasing blocks, e.g. arrays, words, groups
• CPC Class Codes: G11C 2216/18 Flash erasure of all the cells in an array, sector or block simultaneously

Abstract

Erase operations are performed on a flash memory device by monitoring the entropic nature of the flash memory device. In one implementation, flash abstraction logic, tracks how many physical sectors are free to receive data; track how many physical sectors contain data that is dirty, and compare whether the physical sectors that are free to receive data outnumber the physical sectors that contain data that is dirty. A compactor performs an erase operation of one or more blocks when the physical sectors that contain data that is dirty outnumber the physical sectors that are free to receive data. In another implementation, the flash abstraction logic tracks how many physical sector addresses are free to receive data, and track when the physical sector addresses that are free to receive data are insufficient in quantity to receive write requests from a file system. The compactor executes an erase operation of one or more blocks if the physical sector addresses that are free to receive data are insufficient in quantity.

Claims

1. A method for managing erasures on a flash memory device having addressable physical sectors organized as blocks, comprising:

tracking how many physical sectors are free to receive data;

tracking how many physical sectors contain data that is dirty;

comparing whether the physical sectors that are free to receive data outnumber the physical sectors that contain data that is dirty; and

executing an erase operation of one or more blocks when the physical sectors that contain data that is dirty outnumber the physical sectors that are free to receive data.

2. The method as recited in claim 1, further comprising:

scheduling the execution of the erase operation as a low priority thread.

3. The method as recited in claim 1, further comprising:

tracking when the physical sectors that are free to receive data are insufficient in quantity to receive write requests from a file system; and

executing a second erase operation of one or more blocks if the physical sectors that are free to receive data are insufficient in quantity.

4. The method as recited in claim 3, further comprising scheduling the execution of the second erase operation as high priority thread.

5. One or more computer-readable media comprising computer executable instructions that, when executed, perform the method as recited in claim 1.

6. A method for managing erasures on a flash memory device having addressable physical sectors organized as blocks, comprising:

tracking how many physical sectors are free to receive data;

tracking when the physical sectors that are free to receive data are insufficient in quantity to receive write requests from a file system; and

executing an erase operation of one or more blocks if the physical sectors that are free to receive data are insufficient in quantity.

7. The method as recited in claim 6, further comprising scheduling the execution of the erase operation as high priority thread.

8. The method as recited in claim 6, further comprising:

tracking how many physical sectors contain data that is dirty;

comparing whether the physical sectors that are free to receive data outnumber the physical sectors that contain data that is dirty; and

executing a second erase operation of one or more blocks when the physical sectors that contain data that is dirty outnumber the physical sectors that are free to receive data.

9. The method as recited in claim 8, further comprising:

scheduling the execution of the second erase operation as a low priority thread.

10. One or more computer-readable media comprising computer executable instructions that, when executed, perform the method as recited in claim 6.

11. A system for flash memory having addressable locations organized as blocks, comprising:

flash abstraction logic, configured to track how many physical sectors are free to receive data;

track how many physical sectors contain data that is dirty, and compare whether the physical sectors that are free to receive data outnumber the physical sectors that contain data that is dirty; and

a compactor, configured to perform an erase operation of one or more blocks when the physical sectors that contain data that is dirty outnumber the physical sectors that are free to receive data.

12. The system as recited in claim 11, wherein when the compactor performs an erase operation, the compactor advances through a sequence of the physical sector addresses and if a particular physical sector address corresponding to a physical sector in the memory contains valid data, the compactor moves the valid data to a physical sector address corresponding to a physical sector in the memory that is free to receive data before performing the erase operation.

13. The system as recited in claim 11, wherein the compactor performs the erase operation as low priority thread.

14. The system as recited in claim 11, wherein the flash abstraction logic is further configured to track how many physical sector addresses are free to receive data,

track when the physical sector addresses that are free to receive data are insufficient in quantity to receive write requests from a file system; and

the compactor is further configured to execute an erase operation of one or more blocks if the physical sector addresses that are free to receive data are insufficient in quantity.

15. A system for flash memory having addressable locations organized as blocks, comprising:

flash abstraction logic configured to track how many physical sector addresses are free to receive data, and track when the physical sector addresses that are free to receive data are insufficient in quantity to receive write requests from a file system; and

a compactor, configured to execute an erase operation of one or more blocks if the physical sector addresses that are free to receive data are insufficient in quantity.

16. The system as recited in claim 15, wherein when the compactor performs an erase operation, the compactor advances through a sequence of the physical sector addresses and if a particular physical sector address corresponding to a physical sector in the memory contains valid data, the compactor moves the valid data to a physical sector address corresponding to a physical sector in the memory that is free to receive data before performing the erase operation.

17. The system as recited in claim 15, wherein the flash abstraction logic is further configured to track how many physical sectors are free to receive data;

track how many physical sectors contain data that is dirty, and compare whether the physical sectors that are free to receive data outnumber the physical sectors that contain data that is dirty; and

the compactor, is further configured to perform an erase operation of one or more blocks when the physical sectors that contain data that is dirty outnumber the physical sectors that are free to receive data.

18. The system as recited in claim 15, wherein the compactor performs the erase operation as a high priority thread.

19. One or more computer-readable media comprising computer-executable instructions that, when executed by a computer, causes the computer to:

organize a flash memory having addressable locations into blocks;

track how many physical sectors are free to receive data;

track how many physical sectors contain data that is dirty;

compare whether the physical sectors that are free to receive data outnumber the physical sectors that contain data that is dirty; and

perform an erase operation of one or more blocks when the physical sectors that contain data that is dirty outnumber the physical sectors that are free to receive data.

20. One or more computer-readable media as recited in claim 19, that causes the computer when performing the erase operation to:

advance through a sequence of the physical sector addresses; and

if a particular physical sector address corresponding to a physical sector in the memory contains valid data, to move the valid data to a physical sector address corresponding to a physical sector in the memory that is free to receive data before performing the erase operation.

21. One or more computer-readable media as recited in claim 19, wherein the computer treats the erase operation as low priority thread.

22. One or more computer-readable media as recited in claim 19, that causes the computer to:

further track how many physical sector addresses are free to receive data, track when the physical sector addresses that are free to receive data are insufficient in quantity to receive write requests from a file system; and

perform an erase operation of one or more blocks if the physical sector addresses that are free to receive data are insufficient in quantity.

23. One or more computer-readable media comprising computer-executable instructions that, when executed by a computer, causes the computer to:

organize a flash memory having addressable locations into blocks;

track how many physical sector addresses are free to receive data;

track when the physical sector addresses that are free to receive data are insufficient in quantity to receive write requests from a file system; and

execute an erase operation of one or more blocks if the physical sector addresses that are free to receive data are insufficient in quantity.

24. One or more computer-readable media as recited in claim 23, that causes the computer when performing the erase operation to:

advance through a sequence of the physical sector addresses; and

if a particular physical sector address corresponding to a physical sector in the memory contains valid data, to move the valid data to a physical sector address corresponding to a physical sector in the memory that is free to receive data before performing the erase operation.

25. One or more computer-readable media as recited in claim 23, that causes the computer to further track how many physical sectors are free to receive data;

track how many physical sectors contain data that is dirty, and compare whether the physical sectors that are free to receive data outnumber the physical sectors that contain data that is dirty; and

perform an erase operation of one or more blocks when the physical sectors that contain data that is dirty outnumber the physical sectors that are free to receive data.

26. One or more computer-readable media as recited in claim 23, wherein the computer treats the erase operation as a high priority thread.