Memory system and method for controlling a nonvolatile semiconductor memory

• US 9,417,799 B2
• Filed: 06/17/2015
• Issued: 08/16/2016
• Est. Priority Date: 03/01/2008
• Status: Active Grant

• Current Assignee: Kioxia Corporation
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Yano, Junji, Hatsuda, Kosuke, Matsuzaki, Hidenori, Okamoto, Wataru
• Primary Examiner(s): Parikh, Kalpit
• Application Number:
  US14/742,374
• Publication Number:
  US 20150309728A1
• Time in Patent Office: 426 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2206/1014 One time programmable [OTP] memory, e.g. PROM, WORM
• CPC Class Codes: G06F 2212/7203 Temporary buffering, e.g. using volatile buffer or dedicated buffer blocks
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0661 Format or protocol conversion arrangements
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/102 External programming circuits, e.g. EPROM programmers; In-circuit programming or reprogramming; EPROM emulators
• CPC Class Codes: G11C 2211/5643 Multilevel memory comprising cache storage devices
• CPC Class Codes: G11C 2211/5646 Multilevel memory with flag bits, e.g. for showing that a "first page" of a word line is programmed but not a "second page"

Abstract

A memory system includes a nonvolatile semiconductor memory having blocks, the block being data erasing unit; and a controller configured to execute; an update processing for; writing superseding data in a block, the superseding data being treated as valid data; and invalidating superseded data having the same logical address as the superseding data, the superseded data being treated as invalid data; and a compaction processing for; retrieving blocks having invalid data using a management table, the management table managing blocks in a linked list format for each number of valid data included in the block; selecting a compaction source block having at least one valid data from the retrieved blocks; copying a plurality of valid data included in the compaction source blocks into a compaction target block; invalidating the plurality of valid data in the compaction source blocks; and releasing the compaction source blocks in which all data are invalidated.

Claims

1. A memory system comprising:

a nonvolatile semiconductor memory including a plurality of storage units;

a volatile semiconductor memory including a storage area;

a controller configured to;

select valid data stored in first storage units;

store write data in the storage area, the write data being sent from a host apparatus;

write the selected valid data, as first valid data, in a second storage unit, when a sum of the valid data stored in the first storage units does not reach a size of a unit of storage;

copy, as second valid data, the write data stored in the storage area, to the second storage unit, when the write data stored in the storage area reaches a size of a unit of management of the valid data; and

write the first valid data and the second valid data stored in the second storage unit, in a third storage unit, when a total size of the first valid data and the second valid data stored in the second storage unit reaches the size of the unit of storage.

2. The memory system according to claim 1, wherein

the valid data is managed by the size of the unit of management, the size of the unit of management being larger than a size of one page, wherein

the size of one page is a unit of writing for the nonvolatile semiconductor memory, wherein

the size of the unit of management is smaller than a size of a unit of data erasing for the nonvolatile semiconductor memory.

3. The memory system according to claim 1, wherein

the controller is configured to manage a plurality of blocks using link information, the link information being a plurality of linked lists, wherein

the linked lists are configured to link blocks that have a same number of valid data.

4. The memory system according to claim 3, wherein

the linked lists include a first linked list and a second linked list, wherein

the first linked list manages blocks that have a first number of valid data, wherein

the second linked list manages blocks that have a second number of valid data, wherein

the first number is smaller than the second number, wherein

the first number and the second number are selected from among numbers of 1 to N−

1.

5. The memory system according to claim 1, wherein

the first storage units are compaction source blocks, the size of the unit of storage being a size of one block, wherein

the controller is configured to acquire a first compaction target block and rewrite the selected valid data in the first compaction target block, when a sum of valid data stored in the compaction source blocks reaches the size of one block.

6. The memory system according to claim 1, wherein

the first storage units are compaction source blocks, the size of the unit of storage being a size of one block, wherein

the controller is configured to rewrite the selected valid data in the second storage unit, as the first valid data, when a sum of valid data stored in the compaction source blocks does not reach the size of one block.

7. The memory system according to claim 6, wherein

the controller is configured to copy, as the second valid data, the write data stored in the storage area, to the second storage unit, when the write data stored in the storage area reaches the size of the unit of management, wherein

the controller is configured to rewrite the first valid data and the second valid data stored in the second storage unit, in a second compaction target block, when the total size of the first valid data and the second valid data stored in the second storage unit reaches the size of one block.

8. The memory system according to claim 7, wherein

the controller is configured to release a block allocated to the second storage unit, after rewriting the first valid data and the second valid data stored in the second storage unit.

9. A compaction method comprising:

storing data in a nonvolatile semiconductor memory, the nonvolatile semiconductor memory including a plurality of storage units;

selecting valid data stored in first storage units;

storing write data in a storage area included in a volatile semiconductor memory, the write data being sent from a host apparatus;

writing the selected valid data, as first valid data, in a second storage unit, when a sum of the valid data stored in the first storage units does not reach a size of a unit of storage;

copying, as second valid data, the write data stored in the storage area, to the second storage unit, when the write data stored in the storage area reaches a size of a unit of management of the valid data; and

writing the first valid data and the second valid data stored in the second storage unit, in a third storage unit, when a total size of the first valid data and the second valid data stored in the second storage unit reaches the size of the unit of storage.

10. The method according to claim 9, wherein

the valid data is managed by the size of the unit of management, the size of the unit of management being larger than a size of one page, wherein

the size of one page is a unit of writing for the nonvolatile semiconductor memory, wherein

the size of the unit of management is smaller than a size of a unit of data erasing for the nonvolatile semiconductor memory.

11. The method according to claim 9, wherein

a plurality of blocks are managed using link information, the link information being a plurality of linked lists, wherein

the linked lists are configured to link blocks that have a same number of valid data.

12. The method according to claim 11, wherein

the linked lists include a first linked list and a second linked list, wherein

the first linked list manages blocks that have a first number of valid data, wherein

the second linked list manages blocks that have a second number of valid data, wherein

the first number is smaller than the second number, wherein

the first number and the second number are selected from among numbers of 1 to N−

1.

13. The method according to claim 9, wherein

the first storage units are compaction source blocks, the size of the unit of storage being a size of one block, wherein

a first compaction target block is acquired and the selected valid data is rewritten in the first compaction target block, when a sum of valid data stored in the compaction source blocks reaches the size of one block.

14. The method according to claim 9, wherein

the first storage units are compaction source blocks, the size of the unit of storage being a size of one block, wherein

the selected valid data is rewritten in the second storage unit, as the first valid data, when a sum of valid data stored in the compaction source blocks does not reach the size of one block.

15. The method according to claim 14, wherein

the write data stored in the storage area is copied, as the second valid data, to the second storage unit, when the write data stored in the storage area reaches the size of the unit of management, wherein

the first valid data and the second valid data stored in the second storage unit are rewritten in a second compaction target block, when the total size of the first valid data and the second valid data stored in the second storage unit reaches the size of one block.

16. The method according to claim 15, wherein

a block allocated to the second storage unit is released, after rewriting the first valid data and the second valid data stored in the second storage unit.