MEMORY MANAGEMENT DEVICE AND METHOD, PROGRAM, AND MEMORY MANAGEMENT SYSTEM

• US 20080235467A1
• Filed: 03/13/2008
• Published: 09/25/2008
• Est. Priority Date: 03/23/2007
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tagawa, Yojiro
• Granted Patent: US 8,335,893 B2
• Time in Patent Office: Days
• US Class Current: 711/154
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/08 in hierarchically structured memory systems, e.g. virtual memory systems
• CPC Class Codes: G06F 2212/7202 Allocation control and policies
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0673 Single storage device

Abstract

A memory management device which is capable of allocating a memory unit accessible at a higher speed to data which is stored in a storage device having memory units different in access speed, without being limited in an storage area. The storage device comprises a BLC flash memory accessible at a predetermined access speed, an MLC flash memory accessible at a lower access speed than the predetermined access speed, a controller, and a RAM. The controller manages the BLC flash memory and the BLC flash memory in units each formed by a plurality of physical pages, and writes data in the physical pages, and the RAM holds page allocation information in which logical pages designated when writing data and the physical pages are associated with each other.

Claims

1. A memory management device comprising:

a first memory unit configured to be accessible at a predetermined access speed;

a second memory unit configured to be accessible at a lower access speed than the predetermined access speed;

a control unit configured to manage said first and second memory units in units of data-holding units each formed by a plurality of physical pages and write data in the physical pages; and

a storage unit configured to store page allocation information in which logical pages designated when writing the data and the physical pages are associated with each other,

wherein said control unit is operable when writing data in one of said first memory unit and said second memory unit, to write the data in said first memory unit based on the page allocation information corresponding to the designated logical pages.

2. A memory management device as claimed in claim 1, wherein said control unit designates the predetermined access speed as an access speed in the page allocation information, thereby causing the data to be written in said first memory unit.

3. A memory management device as claimed in claim 1, further comprising an access frequency-determining unit configured to determine a frequency of access to the logical pages, and

wherein when said access frequency-determining unit determines that the access frequency is high, said control unit designates the predetermined access speed as an access speed in the page allocation information, thereby causing the data to be written in said first memory unit.

4. A memory management device as claimed in claim 1, further comprising a determination unit configured to determine, based on the page allocation information, whether or not the logical pages have associated ones of the physical pages allocated thereto,

a change unit configured to change physical pages for formerly holding data of the logical pages which are determined by said determination unit to have the associated physical pages allocated thereto, to erasure waiting pages, and

a garbage collection unit configured to be operable when an erasure waiting page count exceeds a threshold value, to move the data written in the physical pages to other physical pages and carry out a garbage collection process for changing management information on an associated one of the data-holding units to thereby bring the physical pages into an erased state.

5. A memory management device as claimed in claim 4, wherein said garbage collection unit carries out the garbage collection process whenever writing of the data is performed.

6. A memory management device as claimed in claim 4, wherein said garbage collection unit periodically carries out the garbage collection process as a background process.

7. A memory management device as claimed in claim 4, wherein said control unit is operable when data written in the physical pages is to be moved to other physical pages by said garbage collection unit, to designate an access speed for the logical pages before moving of the data as an access speed for the logical pages to which the other physical pages are allocated.

8. A memory management device as claimed in claim 4, wherein said control unit is operable when data written in the physical pages is to be moved to other physical pages by said garbage collection unit, to designate an access speed for the logical pages to which the other physical pages are allocated according to a frequency of access to the logical pages.

9. A memory management device as claimed in claim 7, wherein said control unit is operable when the access speed is designated for the logical pages, to write the data associated with the logical pages in the physical pages to which the data is to be moved, and updates the page allocation information.

10. A memory management method comprising:

a management step of managing a first memory unit configured to be accessible at a predetermined access speed and a second memory unit configured to be accessible at a lower access speed than the predetermined access speed, in units of data-holding units each formed by a plurality of physical pages;

a storage step of storing page allocation information in which logical pages designated when writing the data and the physical pages are associated with each other, in one of the first memory unit and the second memory unit; and

a writing step of writing, when writing data in one of the first memory unit and the second memory unit, the data in the first memory unit based on the page allocation information corresponding to the designated logical pages.

11. A computer readable program for causing a computer to execute a memory management method, wherein the program comprises:

a management module for managing a first memory unit configured to be accessible at a predetermined access speed and a second memory unit configured to be accessible at a lower access speed than the predetermined access speed, in units of data-holding units each formed by a plurality of physical pages;

a storage module for storing page allocation information in which logical pages designated when writing the data and the physical pages are associated with each other, in one of the first memory unit and the second memory unit; and

a writing module for writing, when writing data in one of the first memory unit and the second memory unit, the data in the first memory unit based on the page allocation information corresponding to the designated logical pages.

12. A memory management system connected to a memory management device, comprising:

a host system configured to have a predetermined file system operating thereon,

wherein the memory management device includes a first memory unit configured to be accessible at a predetermined access speed, a second memory unit configured to be accessible at a lower access speed than the predetermined access speed, a control unit configured to manage said first and second memory units in units of data-holding units each formed by a plurality of physical pages and write data in the physical pages, and a storage unit configured to store page allocation information in which logical pages designated when writing the data and the physical pages are associated with each other, wherein said control unit is operable when writing data in one of said first memory unit and said second memory unit, to write the data in said first memory unit based on the page allocation information corresponding to the designated logical pages, and

wherein said host system is operable when formatting by the predetermined file system, to designate said first memory unit as a management area used by the predetermined file system.

13. A memory management system connected to a memory management device, comprising:

a host system configured to have a predetermined file system operating thereon,

wherein the memory management device includes a first memory unit configured to be accessible at a predetermined access speed, a second memory unit configured to be accessible at a lower access speed than the predetermined access speed, a control unit configured to manage said first and second memory units in units of data-holding units each formed by a plurality of physical pages and write data in the physical pages, and a storage unit configured to store page allocation information in which logical pages designated when writing the data and the physical pages are associated with each other, wherein said control unit is operable when writing data in one of said first memory unit and said second memory unit, to write the data in said first memory unit based on the page allocation information corresponding to the designated logical pages, and

wherein said host system is operable when generating files and directories by the predetermined file system, to designate said first memory unit as a management area used by the predetermined file system.