UFS based idle time garbage collection management

• US 10,521,146 B1
• Filed: 11/09/2017
• Issued: 12/31/2019
• Est. Priority Date: 11/09/2017
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Tanpairoj, Kulachet, Huang, Jianmin, Muchherla, Kishore Kumar
• Primary Examiner(s): Yi, David
• Assistant Examiner(s): Goldschmidt, Craig S
• Application Number:
  US15/808,567
• Time in Patent Office: 782 Days
• Field of Search: None
• CPC Class Codes: G06F 1/3225 of memory devices
• CPC Class Codes: G06F 1/3234 Power saving characterised by the action undertaken
• CPC Class Codes: G06F 1/324 by lowering clock frequency
• CPC Class Codes: G06F 1/3275 Power saving in memory, e.g. RAM, cache
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0253 Garbage collection, i.e. reclamation of unreferenced memory
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0688 Non-volatile semiconductor memory arrays
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

Disclosed in some examples are systems, methods, NAND memory devices, and machine readable mediums for intelligent SLC cache migration processes that move data written to SLC cache to MLC storage based upon a set of rules that are evaluated using the state of the NAND device. In some examples, the SLC cache migration process may utilize a number of NAND operational parameters to determine when to move the data written to SLC cache to MLC, how much data to move from SLC to MLC, and the parameters for moving the data.

Claims

1. A method of operating a NAND device, the method comprising:

at a NAND controller;

retrieving an SLC cache migration profile, the SLC cache migration profile including a first and second initiation rule for initiating a migration of data stored in an SLC cache to MLC memory cells, the first and second rules comprising one of;

an idle rule, a data fragmentation rule, a current block erase count, a current Write Amplification Factor (WAF), or a power consumption level rule, wherein the first rule is different than the second rule;

retrieving a first NAND operational condition specified by the first rule, and determining that the first NAND operational condition satisfies the first rule;

retrieving a second NAND operational condition specified by the second rule, and determining that the second NAND operational condition satisfies the second rule; and

responsive to the first and second rule being satisfied, migrating at least a portion of data stored in the SLC cache to MLC memory cells of the NAND device.

2. The method of claim 1, wherein the SLC cache migration profile includes a termination condition, and wherein migrating the at least a portion of data stored in the SLC cache to MLC memory cells of the NAND device comprises:

determining that the termination condition is satisfied, the termination condition corresponding to a NAND operational condition; and

responsive to the termination condition being satisfied, terminating the migration, wherein the termination condition is not a completion of the migration.

3. The method of claim 2, wherein the termination condition is a power usage.

4. The method of claim 1, comprising:

receiving the SLC cache migration profile from a host device across a host interface.

5. The method of claim 1, comprising:

determining, based upon the SLC migration profile, a rate for the migration operations, and wherein migrating the at least the portion of data stored in the SLC cache to MLC memory cells of the NAND comprises migrating the at least the portion of data stored in the SLC cache to MLC memory cells of the NAND at the rate.

6. The method of claim 1, comprising:

garbage collecting SLC memory cells where data was stored that was migrated to MLC memory cells.

7. The method of claim 1, wherein migrating at least a portion of data stored in an SLC cache to MLC memory cells of the NAND device comprises determining from the SLC migration profile a migration parameter rule.

8. The method of claim 7, wherein the migration parameter rule includes a rule that determines a speed of the migration depending on an operational parameter of the NAND device.

9. A machine readable medium, comprising instructions, which when performed by a machine, causes the machine to perform operations comprising:

retrieving an SLC cache migration profile, the SLC cache migration profile including a first and second initiation rule for initiating a migration of data stored in an SLC cache of a NAND memory device to MLC memory cells, the first and second rules comprising one of;

an idle rule, a data fragmentation rule, a current block erase count, a current Write Amplification Factor (WAF), or a power consumption level rule, wherein the first rule is different than the second rule;

retrieving a first NAND operational condition specified by the first rule, and determining that the first NAND operational condition satisfies the first rule;

retrieving a second NAND operational condition specified by the second rule, and determining that the second NAND operational condition satisfies the second rule; and

responsive to the first and second rule being satisfied, migrating at least a portion of data stored in the SLC cache to MLC memory cells of the NAND device.

10. The machine readable medium of claim 9, wherein the SLC cache migration profile includes a termination condition, and wherein the operations of migrating the at least a portion of data stored in the SLC cache to MLC memory cells of the NAND device comprises:

determining that the termination condition is satisfied, the termination condition corresponding to a NAND operational condition; and

responsive to the termination condition being satisfied, terminating the migration, wherein the termination condition is not a completion of the migration.

11. The machine readable medium of claim 10, wherein the termination condition is a power usage.

12. The machine readable medium of claim 9, wherein the operations further comprise:

receiving the SLC cache migration profile from a host device across a host interface.

13. The machine readable medium of claim 9, wherein the operations further comprise:

determining, based upon the SLC migration profile, a rate for the migration operations, and wherein migrating the at least the portion of data stored in the SLC cache to MLC memory cells of the NAND comprises migrating the at least the portion of data stored in the SLC cache to MLC memory cells of the NAND at the rate.

14. The machine readable medium of claim 9, wherein the operations further comprise:

garbage collecting SLC memory cells where data was stored that was migrated to MLC memory cells.

15. The machine readable medium of claim 9, wherein the operations of migrating at least a portion of data stored in an SLC cache to MLC memory cells of the NAND device comprises determining from the SLC migration profile a migration parameter rule.

16. The machine readable medium of claim 15, wherein the migration parameter rule includes a rule that determines a speed of the migration depending on an operational parameter of the NAND device.

17. A NAND device, comprising:

a controller configured to perform operations comprising;

retrieving an SLC cache migration profile, the SLC cache migration profile including a first and second initiation rule for initiating a migration of data stored in an SLC cache of a NAND memory device to MLC memory cells, the first and second rules comprising one of;

an idle rule, a data fragmentation rule, a current block erase count, a current Write Amplification Factor (WAF), or a power consumption level rule, wherein the first rule is different than the second rule;

retrieving a first NAND operational condition specified by the first rule, and determining that the first NAND operational condition satisfies the first rule;

retrieving a second NAND operational condition specified by the second rule, and determining that the second NAND operational condition satisfies the second rule; and

responsive to the first and second rule being satisfied, migrating at least a portion of data stored in the SLC cache to MLC memory cells of the NAND device.

18. The NAND device of claim 17, wherein the SLC cache migration profile includes a termination condition, and wherein the operations of migrating the at least a portion of data stored in the SLC cache to MLC memory cells of the NAND device comprises:

determining that the termination condition is satisfied, the termination condition corresponding to a NAND operational condition; and

responsive to the termination condition being satisfied, terminating the migration, wherein the termination condition is not a completion of the migration.

19. The NAND device of claim 18, wherein the termination condition is a power usage.

20. The NAND device of claim 17, wherein the operations further comprise:

receiving the SLC cache migration profile from a host device across a host interface.

21. The NAND device of claim 17, wherein the operations further comprise:

determining, based upon the SLC migration profile, a rate for the migration operations, and wherein migrating the at least the portion of data stored in the SLC cache to MLC memory cells of the NAND comprises migrating the at least the portion of data stored in the SLC cache to MLC memory cells of the NAND at the rate.

22. The NAND device of claim 17, wherein the operations further comprise:

garbage collecting SLC memory cells where data was stored that was migrated to MLC memory cells.

23. The NAND device of claim 17, wherein the operations of migrating at least a portion of data stored in an SLC cache to MLC memory cells of the NAND device comprises determining from the SLC migration profile a migration parameter rule.

24. The NAND device of claim 23, wherein the migration parameter rule includes a rule that determines a speed of the migration depending on an operational parameter of the NAND device.