JP5967307B2 - Information processing apparatus, control circuit, control program, and control method - Google Patents

Description

  The present invention relates to an information processing device, a control circuit, a control program, and a control method.

  Conventionally, an information processing apparatus using a nonvolatile memory that operates at a higher speed than a magnetic disk is known. As an example of such an information processing system, an information processing apparatus using a NAND flash memory device as a storage device such as a storage is known. In the following description, the NAND flash memory device is described as a NAND device.

  Here, the NAND device performs data write, read, and data update movement in units of physical pages that are data storage areas, and erases data in units of physical blocks including a plurality of physical pages. For this reason, the NAND device may have a physical block in which valid data and invalid data are mixed. In addition, since the device deteriorates when erasing data in the NAND device, the device deteriorates between a physical page in which frequently updated data is written and a physical page in which less frequently updated data is written. Variation occurs in the speed at which it is performed.

  For this reason, a NAND controller is known that performs data migration and leveling of deterioration by moving data written to each physical block according to the data write status and data write time for each physical block. It has been. For example, the NAND controller has, for each physical block, a management information table in which information indicating whether or not the data of each physical page is valid and information indicating the time when the data was last written are stored.

  Then, the NAND controller refers to the management information table, and determines whether to move the data for each physical block according to the number of valid data and the time elapsed since the data was written. After that, if the NAND controller determines to move the data, the valid data written in the physical block is moved to the physical page of the spare block, and the new physical data is deleted by deleting the data of the selected physical block. Secure spare blocks and level out deterioration.

  The NAND controller also has an address conversion table that converts a logical address used for specifying data by a system executed by the information processing apparatus into a physical address indicating a physical page in which data is stored. Then, when the data is moved, the NAND controller updates the address conversion table using the physical address indicating the data movement source and the data movement destination.

  For example, there are the following techniques as conventional techniques. The NAND controller reversely converts a physical address indicating a data movement source into a logical address by using an address reverse conversion table that reversely converts a physical address into a logical address. Then, the NAND controller rewrites the physical address using the reversely converted logical address as an index among the physical addresses stored in the address conversion table to the physical address indicating the data movement destination.

  In addition, in order to improve the access speed to the flash memory, there is a conventional technique for specifying a storage area to which a plurality of logically continuous data is written and writing a plurality of data in a distributed manner.

JP 2009-003784 A JP 2003-15944 A

  However, in the technique for determining whether to move data for each physical block described above, the address conversion table is updated using the physical address indicating the data movement source and the data movement destination. In order to perform such processing, for example, the NAND controller has an address reverse conversion table for performing reverse conversion from a physical address indicating a data movement source to a logical address, which causes a problem that the circuit scale increases. Further, even when a conventional technique for writing a plurality of data in a distributed manner is used, conversion from a physical address to a logical address is not considered, and it is difficult to avoid using an address reverse conversion table.

  The disclosed technique has been made in view of the above, and an object thereof is to provide an information processing apparatus, a control circuit, a control program, and a control method that improve access performance while suppressing the circuit scale of a NAND controller. .

  In one aspect, an information processing device, a control circuit, a control program, and a control method disclosed in the present application have a plurality of storage areas. The start position setting unit sets, for each block including a plurality of the storage areas, a logical address satisfying a predetermined condition among the logical addresses corresponding to the physical addresses for identifying the storage areas included in each block as a search start position. The selection unit selects a logical address in a predetermined order from the search start position of the conversion table representing the correspondence between the logical address and the physical address. The acquisition unit acquires a physical address associated with the logical address selected by the selection unit from the conversion table. The determination unit determines whether to move the data stored in the storage area indicated by the physical address acquired by the acquisition unit using a predetermined condition. When the determining unit determines to move the data, the moving unit moves the data stored in the storage area indicated by the physical address acquired by the acquiring unit to another storage area. The update unit updates a physical address associated with the logical address selected by the selection unit, among physical addresses stored in the conversion table, to a physical address indicating the other storage area.

  According to one aspect of the information processing device, the control circuit, the control program, and the control method disclosed in the present application, it is possible to improve the access performance while suppressing the circuit scale of the NAND controller.

FIG. 1 is a schematic configuration diagram of an information processing apparatus according to the first embodiment. FIG. 2 is a diagram for explaining an example of memory access. FIG. 3 is a block diagram of the NAND controller according to the first embodiment. FIG. 4 is a diagram illustrating an example of an address conversion table according to the first embodiment. FIG. 5 is a diagram of an example of the management information table according to the first embodiment. FIG. 6 is a schematic diagram illustrating an example of a process executed by the NAND controller according to the first embodiment. FIG. 7 is a flowchart of processing executed by the NAND controller according to the first embodiment. FIG. 8 is a flowchart of the update process of the minimum logical address of the management information table according to the first embodiment. FIG. 9 is a diagram illustrating an example of a management information table according to the second embodiment. FIG. 10 is a flowchart of a process executed by the NAND controller according to the second embodiment. FIG. 11 is a flowchart of the update process of the maximum logical address of the management information table according to the second embodiment. FIG. 12 is a diagram of an example of a NAND controller that executes a control program.

  Hereinafter, embodiments of an information processing apparatus, a control circuit, a control program, and a control method disclosed in the present application will be described in detail with reference to the drawings. It should be noted that the information processing apparatus, control circuit, control program, and control method disclosed in the present application are not limited by the following embodiments.

  FIG. 1 is a schematic configuration diagram of an information processing apparatus according to the first embodiment. The information processing apparatus 1 includes a plurality of memories 2a and 2b, a plurality of CPUs (Central Processing Units) 3a and 3b, an I / O (Input Output) hub 4, and a plurality of SSDs (Solid State Drives) 5a and 5b. . The SSD 5a includes a NAND controller 6a and a plurality of NAND devices 7a to 10a.

  The SSD 5b includes a NAND controller 6b and a plurality of NAND devices 7b to 10b. In the following description, the SSD 5b, the NAND controller 6b, and the plurality of NAND devices 7b to 10b perform the same functions as the SSD 5a, the NAND controller 6a, and the plurality of NAND devices 7a to 10a, and the description thereof is omitted. To do.

  The memories 2a and 2b are storage devices that store data used by the CPUs 3a and 3b for arithmetic processing. The CPUs 3a and 3b are arithmetic processing devices that perform various arithmetic processes using data stored in the memories 2a and 2b. For example, the CPUs 3a and 3b use NUMA (Non-Uniform Memory Access) technology to acquire data stored in the memories 2a and 2b, and execute arithmetic processing using the acquired data.

  In addition, the CPUs 3a and 3b acquire data stored in the SSDs 5a and 5b via the I / O hub 4, and execute arithmetic processing using the acquired data. Specifically, the CPU 3a issues a data read request or write request to the SSD 5a, and reads or writes data from each NAND device 7a to 10a. For example, the CPU 3a issues a read request storing a logical address designating data to be read to the SSD 5a. In addition, the CPU 3a issues a write request in which a logical address that specifies a data write destination and data to be written are stored.

  The NAND device 7a is a nonvolatile memory that stores various data. More specifically, the NAND device 7a has a plurality of physical pages, which are data storage areas, and writes data in units of physical pages. The NAND device 7a has a plurality of physical blocks having a plurality of physical pages, and erases data in units of blocks. Here, one physical page has a storage capacity of, for example, 8 kilobytes, and one physical block has, for example, 128 physical pages.

  The NAND controller 6a accesses each of the NAND devices 7a to 10a, and reads and writes data. For example, the NAND controller 6a associates a logical address used when the CPUs 3a and 3b specify a storage area in which data is stored with a physical address indicating a storage area of the NAND devices 7a to 10a in which the data is stored. An address translation table.

  When the NAND controller 6a receives the logical address together with the read request, the NAND controller 6a uses the address conversion table to identify the physical address associated with the logical address, and reads data from the storage area indicated by the identified physical address. . Thereafter, the NAND controller 6a transmits the read data to the CPU 3a via the I / O hub 4.

  In the following description, in order to facilitate understanding, a logical address that is the start address of each physical page is simply described as a logical address, and a physical address that is the start address of each physical page is simply described as a physical address. In addition, the system executed by the information processing apparatus 1 issues a read request and a write request for a logical address that is a head address of each physical page.

For example, NAND controller 6a is NAND device 7a~10a has a plurality of blocks, if it contains ^{2 q} number of physical pages in each block, the following processing is performed. First, the NAND controller 6a uses the lower q bits of the logical address as a logical page number for identifying a physical page in one logical block, and the upper p bits of the remaining logical addresses as one logical block. Is a logical block address.

  Further, the NAND controller 6a uses the upper p bits of the physical address as a physical block address indicating one physical block, and the lower q bits of the physical address identify each physical page within one physical block. Physical page number. That is, the NAND controller 6a divides a logical address into a logical block address indicating a logical block and a logical page number indicating a logical page for each logical block. The NAND controller 6a divides the physical address into a physical block address indicating a physical block and a physical page number indicating a physical page for each physical block.

  Hereinafter, an example of memory access executed by the NAND controller 6a will be described with reference to FIG. FIG. 2 is a diagram for explaining an example of memory access. In the example illustrated in FIG. 2, for ease of understanding, the NAND device 7 a in which the number of blocks is “8” and the number of physical pages in each block is “4” is described. In the example shown in FIG. 2, the NAND controller 6a writes data in units of physical pages of the NAND devices 7a to 10a using an address conversion table in which logical block addresses and physical block addresses are associated with each other. Was described.

  For example, as illustrated in FIG. 2A, the NAND controller 6a issues a write request to the logical page number “3” of the logical block address “LB00”, that is, the logical address “L0003” from the file system executed by the CPU 3a. Issue. Then, the NAND controller 6a acquires the physical address “P0403” associated with the logical address “L0003” using the address conversion table, and stores the data before update as shown in FIG. Identifies the physical page being served.

  Subsequently, as shown in FIG. 2C, the NAND controller 6a reads the data of the physical page indicated by the physical address “P0403”, updates the read data to the data to be written, and updates the updated data. Store in free physical page of spare block. As a detailed example, the NAND controller 6a stores the updated data in the physical page indicated by the physical address “P0800”, as shown in FIG. Thereafter, as shown in FIG. 2E, the NAND controller 6a updates the physical address “P0403” associated with the logical address “L0003” to “P0800”, and ends the processing.

  Here, when writing or moving data stored in the NAND devices 7a to 10a in units of physical pages, valid data and invalid data may be mixed in one physical block. For example, in the example illustrated in FIG. 2, when updating the data indicated by the logical address “L0003”, the NAND controller 6a invalidates the data in the physical block indicated by the physical block address “B04”. Then, the NAND controller 6a stores the updated data in the physical block indicated by the physical block address “B08”. Therefore, valid data and invalid data are mixed in the physical block indicated by the physical block address “B04”.

  Here, the NAND devices 7a to 10a cannot overwrite data on a physical page in which invalid data is stored, and write data to a spare block from which data has been erased in advance. However, when the number of physical blocks in which valid data and invalid data are mixed increases, it becomes impossible to secure a spare block for newly writing data. The NAND devices 7a to 10a have elements for holding data. Such an element deteriorates when data is erased, and when the deterioration progresses, it becomes impossible to hold charges appropriately.

  Therefore, the conventional NAND controller executes data movement control for organizing valid data and securing a new spare block.

  Here, when the data movement control such as the garbage collection process is executed, the NAND controller 6a updates the address conversion table according to the data movement. However, the NAND controller 6a determines whether or not to move data for each physical block using page valid of the management information table. Therefore, the NAND controller 6a can identify the data source physical address after performing the data movement control, but cannot identify the logical address corresponding to the data source physical address.

  Therefore, it is conceivable to cause the NAND controller 6a to perform the following processing. First, the NAND controller 6a specifies a block for moving data. Then, the NAND controller 6a refers to the address conversion table and selects one logical address. Next, the NAND controller 6a acquires a physical address associated with the selected logical address from the address conversion table. Then, the NAND controller 6a uses the management information table to determine whether or not the physical block including the physical page indicated by the acquired physical address is a block for moving data. Thereafter, when the data is moved, the NAND controller 6a updates the physical address associated with the selected logical address among the physical addresses stored in the address conversion table to the movement destination physical address. The NAND controller 6a can complete the data movement of all the pages of the block in which data movement is performed by repeating the above processing in order from the first logical address of the address conversion table. However, when data movement determination is performed in order from the first logical address in the address conversion table, processing is performed for all the logical addresses at the maximum, and the data movement process takes a long time.

  Therefore, the information processing apparatus according to the present embodiment specifies the minimum logical address for each block, and uses the minimum logical address as the search start address of the corresponding block, thereby reducing the number of data movement determination processes. The time required for the data movement process is shortened and the access performance is prevented from being lowered. This minimum logical address corresponds to an example of “search start position”.

  Hereinafter, the NAND controller 6a will be described with reference to FIG. FIG. 3 is a block diagram of the NAND controller according to the first embodiment. In the example illustrated in FIG. 3, the NAND controller 6 a includes a table storage unit 11, a requester interface unit 12, a request arbitration unit 13, and a table control unit 14. The NAND controller 6 a includes a device access control unit 15, a cyclic reference control unit 16, and a data movement control unit 17. The table storage unit 11 stores an address conversion table 18 and a management information table 19.

  First, the information stored in the address conversion table 18 and the management information table 19 stored in the table storage unit 11 will be described with reference to FIGS. 4 and 5. FIG. 4 is a diagram illustrating an example of an address conversion table according to the first embodiment. As shown in FIG. 4, the address conversion table 18 stores logical addresses, valid flags, and physical addresses in association with each other. Here, the valid flag is a valid bit indicating whether or not the data stored in the physical page indicated by the associated physical address is valid data.

  For example, in the example illustrated in FIG. 4, the address conversion table 18 stores the logical address “L0000”, the valid flag “0”, and the physical address “P0011” in association with each other. That is, the address conversion table 18 indicates that valid data designated by the logical address “L0000” is not stored in the block indicated by the physical address “P0011”.

  Similarly, in the example illustrated in FIG. 4, the address conversion table 18 stores the logical address “L0001”, the valid flag “0”, and the physical address “P0032” in association with each other. The address conversion table 18 stores a logical address “L0002”, a valid flag “1”, and a physical address “P0003” in association with each other. The address conversion table 18 stores a logical address “L0003”, a valid flag “1”, and a physical block address “P0001” in association with each other. That is, the address conversion table 18 indicates that the data stored in the physical addresses “P0003” and “P0001” are valid data.

  Next, information stored in the management information table 19 will be described with reference to FIG. FIG. 5 is a diagram of an example of the management information table according to the first embodiment. As shown in FIG. 5, the management information table 19 stores a physical block address, the number of valid pages, and a minimum logical address in association with each other.

  Here, the number of valid pages is the number of pages having valid data included in the physical block indicated by the associated physical block address. For example, in the management information table 19, when n valid pages are included in one physical block, the number of valid pages is n.

  The minimum logical address is the smallest address among the logical addresses corresponding to each physical address of the page included in the block indicated by the physical block address.

  For example, in the example shown in FIG. 5, the management information table 19 stores the physical block address “B00”, the number of valid pages “11”, and the minimum logical address “L0012” in association with each other. That is, the management information table 19 indicates that 11 pages are valid among the physical pages included in the physical block indicated by the physical block address “B00”. Further, the management information table 19 indicates that the smallest logical address among the logical addresses corresponding to the physical block address “B00” is “L0012”.

  Further, in the example shown in FIG. 5, the management information table 19 has no valid page and no minimum logical address is set for the physical block address “B01”. Here, when the minimum logical address is not set, in this embodiment, “L0000”, which is the smallest logical address among all the logical addresses, is set as an initial value. In the management information table 19, the physical block address “B02”, the number of valid pages “23”, and the minimum logical address “L0000” are stored in association with each other. The management information table 19 stores the physical block address “B03”, the number of valid pages “41”, and the minimum logical address “L0103” in association with each other. In the management information table 19, it is assumed that the physical block address, the number of valid pages, and the minimum logical address are stored in association with each other.

  Returning to FIG. 3, the requester interface unit 12 is an interface for requests from the CPUs 3a and 3b to the NAND devices 7a to 10a. For example, the requester interface unit 12 receives a read request including a logical address from the CPU 3 a or 3 b via the I / O hub 4. In that case, the requester interface unit 12 outputs a read request to the request arbitration unit 13. Further, when the requester interface unit 12 receives the data read from the NAND devices 7 a to 10 a from the request arbitration unit 13, the requester interface unit 12 transmits the data to the CPU 3 a or 3 b that is the issuer of the read request.

  The requester interface unit 12 receives a write request including data to be written to the NAND devices 7a to 10a and a logical address of data to be written from the CPUs 3a and 3b. In this case, the requester interface unit 12 outputs the received write request to the request arbitration unit 13. When the requester interface unit 12 receives a response from the request arbitration unit 13 to the effect that data writing has been completed, the requester interface unit 12 transmits the response to the CPU 3a or 3b that is the source of the write request.

  The request arbitration unit 13 arbitrates various requests issued by the requester interface unit 12, the data movement control unit 17, and the cyclic reference control unit 16. Specifically, the request arbitration unit 13 receives a read request or a write request from the requester interface unit 12. Further, the request arbitration unit 13 receives from the data movement control unit 17 a movement request that requests the data stored in the NAND devices 7a to 10a to be moved from the currently stored block to another block. Further, the request arbitration unit 13 receives from the data movement control unit 17 an erasure request for requesting erasure of data in the physical block. In addition, the request arbitration unit 13 receives a table reference request for requesting reference to the management information table 19 from the cyclic reference control unit 16.

  The request arbitration unit 13 then arbitrates the read request, write request, move request, erase request, and table reference request received from the requester interface unit 12, the data movement control unit 17, and the cyclic reference control unit 16. For example, the request arbitration unit 13 executes the read request and the write request issued by the requester interface unit 12 with the highest priority so that reading and writing of data from the CPUs 3a and 3b to the NAND devices 7a to 10a are not hindered. For example, the request arbitration unit 13 executes the movement request with priority over the deletion request and the table reference request, and executes the deletion request with priority over the table reference request. In addition, about the rule in which the request arbitration part 13 arbitrates each request | requirement, it is not limited to the process mentioned above, You may apply arbitrary rules.

  Hereinafter, an example of processing executed when the request arbitration unit 13 receives a read request, a write request, a move request, an erase request, and a table reference request will be described. For example, when receiving a read request, the request arbitration unit 13 outputs a logical address included in the read request to the table control unit 14. When the request arbitration unit 13 receives a physical address to be read from the table control unit 14, the request arbitration unit 13 issues a read request storing the received physical address to the device access control unit 15. Thereafter, when the request arbitration unit 13 receives data to be read from the device access control unit 15, the request arbitration unit 13 outputs the received data to the requester interface unit 12.

  Further, when receiving the write request, the request arbitration unit 13 outputs a logical address included in the write request to the table control unit 14. As a result, when the data to be written is new data, the request arbitration unit 13 receives from the table control unit 14 the physical address of the page to which the data is written among the spare blocks in which no data is stored. To do.

  Thereafter, the request arbitration unit 13 issues a write request including the physical address received from the table control unit 14 and the write target data to the device access control unit 15. When the request arbitration unit 13 receives a response from the device access control unit 15 indicating that the data writing has been completed, the request arbitration unit 13 receives a table update request including the physical address of the page to which the data is to be written and the logical address included in the write request. Is output to the table control unit 14. If the request arbitration unit 13 receives from the table control unit 14 a response indicating that the table update has been completed, the request arbitration unit 13 outputs a response to the write request to the requester interface unit 12.

  Further, when the write is intended to update the data, the request arbitration unit 13 receives the physical address of the page storing the update source data from the table control unit 14 as the update source physical address. Further, the request arbitration unit 13 receives from the table control unit 14 the physical address of the page included in the spare block, that is, the physical address of the page that is the data write destination, as the update destination physical address.

  When the request arbitration unit 13 receives the update source physical address and the update destination physical address from the table control unit 14, the request arbitration unit 13 issues an update request for requesting data update to the device access control unit 15. Specifically, the request arbitration unit 13 issues an update request including an update source physical address, an update destination physical address, and data to be written to the device access control unit 15.

  When the request arbitration unit 13 receives a response to the effect that data writing has been completed from the device access control unit 15, the request arbitration unit 13 updates the table update request including the update source physical address, the update destination physical address, and the logical address included in the write request. Is output to the table control unit 14. Thereafter, when the request arbitration unit 13 receives a response to the table update request from the table control unit 14, the request arbitration unit 13 outputs a response to the requester interface unit 12 indicating that the data writing has been completed.

  Further, the request arbitration unit 13 receives a movement request including a movement source physical address that is a physical address of a physical page in which the data to be moved is stored and a logical address for designating the data to be moved from the data movement control unit 17 or the like. To do. In addition, the request arbitration unit 13 makes an inquiry to the table control unit 14 and acquires the physical address of the physical page that is the data transfer destination as the transfer destination physical address.

  Then, the request arbitration unit 13 issues a movement request including the movement source physical address and the movement destination physical address to the device access control unit 15. Further, the request arbitration unit 13 receives from the device access control unit 15 a response indicating that the data movement has been completed. Then, the request arbitration unit 13 outputs to the table control unit 14 a table update request that includes a logical address that specifies data to be moved received from the data movement control unit 17, a movement destination physical address, and a movement source physical address. Thereafter, when the request arbitration unit 13 receives a response to the table update request from the table control unit 14, the request arbitration unit 13 outputs a response indicating that the data movement is completed to the data movement control unit 17.

  Further, the request arbitration unit 13 receives an erasure request including a physical block address indicating a physical block to be erased from the data movement control unit 17 or the like. Upon receiving the erase request, the request arbitration unit 13 issues the received erase request to the device access control unit 15. Upon receiving a response from the device access control unit 15 that the data erasure is complete, the request arbitration unit 13 outputs a table update request including the physical block address stored in the erasure request to the table control unit 14. When the request arbitration unit 13 receives from the table control unit 14 a response indicating that the data update has been completed, the request arbitration unit 13 outputs a response indicating that the data erasure has been completed to the data movement control unit 17.

  When the request arbitration unit 13 receives a table reference request from the cyclic reference control unit 16, the request arbitration unit 13 transmits a reference request for the address conversion table 18 and the management information table 19 to the table control unit 14. When the request arbitration unit 13 receives the address conversion table 18 and the management information table 19 from the table control unit 14, the request arbitration unit 13 outputs the received address conversion table 18 and management information table 19 to the cyclic reference control unit 16.

  The table control unit 14 converts a logical address into a physical address. For example, when the logical address stored in the read request is received from the request arbitration unit 13, the table control unit 14 acquires a physical address associated with the received logical address from the address conversion table 18. Then, the table control unit 14 outputs the acquired physical address to the request arbitration unit 13.

  When the table control unit 14 receives the logical address stored in the write request from the request arbitration unit 13, the table control unit 14 refers to the address conversion table 18 and determines whether the valid flag “1” is associated with the received logical address. To do. When the valid flag “0” is associated with the received logical address, that is, when the data to be written is new data, the table control unit 14 executes the following processing.

  First, the table control unit 14 refers to the management information table 19 and identifies a physical block in which no data is stored, that is, a spare block. For example, the table control unit 14 refers to the management information table 19 and searches for physical blocks whose associated valid page numbers are all “0”, and sets the detected physical block as a spare block. Then, the table control unit 14 outputs the physical address of the physical page included in the spare block to the request arbitration unit 13.

  Note that once the spare block is identified, the table control unit 14 sets the physical address of the physical page included in the same spare block until data is written to all physical pages of the physical page included in the identified spare block. Output. Specifically, the table control unit 14 outputs the physical addresses of physical pages in which no data is written among the physical pages included in the spare block, in the order of physical page numbers. Then, when data is written in all physical pages included in the spare block, the table control unit 14 refers to the management information table 19 and identifies a new spare block.

  On the other hand, when the valid flag “1” is associated with the received logical address, that is, when writing is intended to update data, the table control unit 14 executes the following processing. First, the table control unit 14 outputs the physical address associated with the received logical address to the request arbitration unit 13 as an update source physical address. Further, the table control unit 14 identifies the spare block and outputs the physical address of the physical page in which no data is stored among the physical pages included in the identified spare block to the request arbitration unit 13 as the update destination physical address. .

  Further, when the request arbitration unit 13 receives the movement request, the table control unit 14 receives an inquiry about the movement destination physical address from the request arbitration unit 13. In this case, the table control unit 14 identifies the spare block, and outputs the physical address of the physical page in which no data is stored among the physical pages included in the identified spare block to the request arbitration unit 13 as the movement destination physical address. To do.

  The table control unit 14 updates the address conversion table 18 and the management information table 19 in accordance with data writing, movement, or erasure. For example, when the request arbitration unit 13 writes new data, the table control unit 14 receives a table update request including the physical address of the physical page that is the data write destination and the logical address included in the write request. .

  In this case, the table control unit 14 extracts the physical address and logical address of the physical page that is the data write destination from the table update request. Then, the table control unit 14 updates the valid flag associated with the extracted logical address in the address conversion table 18 to “1”. The table control unit 14 stores the extracted physical address in the address conversion table 18 in association with the extracted logical address.

  Further, the table control unit 14 extracts an entry associated with the physical block address indicated by the extracted physical address from the management information table 19. Then, the table control unit 14 increases the number of valid pages of the extracted entry by one. In addition, the table control unit 14 acquires the minimum logical address of the extracted entry from the management information table 19. Then, the table control unit 14 determines whether or not the logical address of the data to be written is smaller than the acquired minimum logical address. When the logical address of the data to be written is smaller than the acquired minimum logical address, the table control unit 14 writes the logical address of the data to be written to the minimum logical address of the extracted entry. Thereafter, the table control unit 14 outputs a response to the table update request to the request arbitration unit 13.

  When the request arbitration unit 13 updates data, the table control unit 14 receives a table update request including the update source physical address, the update destination physical address, and the logical address included in the write request from the request arbitration unit 13. To do. In this case, the table control unit 14 extracts the update source physical address, the update destination physical address, and the logical address from the table update request. Then, the table control unit 14 updates the physical address associated with the extracted logical address in the address conversion table 18 to the extracted update destination physical address.

  Further, the table control unit 14 extracts an entry associated with the physical block address corresponding to the update source physical address from the management information table 19. Then, the table control unit 14 reduces the number of valid pages of the extracted entry by one.

  Next, the table control unit 14 extracts an entry associated with the update destination physical block address from the management information table 19. Then, the table control unit 14 increases the number of valid pages of the extracted entry by one. In addition, the table control unit 14 acquires the minimum logical address of the extracted entry from the management information table 19. Then, the table control unit 14 determines whether or not the logical address of the data to be updated is smaller than the acquired minimum logical address. If the logical address of the data to be updated is smaller than the acquired minimum logical address, the table control unit 14 writes the logical address of the data to be updated to the minimum logical address of the extracted entry. Thereafter, the table control unit 14 outputs a response to the table update request to the request arbitration unit 13.

  In addition, when the request arbitration unit 13 moves data, the table control unit 14 receives a table update request including a movement source physical address, a movement destination physical address, and a logical address that specifies data to be moved. In this case, the table control unit 14 extracts the movement source physical address, the movement destination physical address, and the logical address from the table update request. Then, the table control unit 14 refers to the address conversion table 18 and updates the physical address associated with the extracted logical address to the extracted destination physical address.

  In addition, the table control unit 14 extracts an entry associated with the physical block address corresponding to the movement source physical address from the management information table 19. Then, the table control unit 14 reduces the number of valid pages of the extracted entry by one.

  Next, the table control unit 14 extracts an entry associated with the destination physical block address from the management information table 19. Then, the table control unit 14 increases the number of valid pages of the extracted entry by one. In addition, the table control unit 14 acquires the minimum logical address of the extracted entry from the management information table 19. Then, the table control unit 14 determines whether or not the logical address of the data to be moved is smaller than the acquired minimum logical address. When the logical address of the data to be moved is smaller than the acquired minimum logical address, the table control unit 14 writes the logical address of the data to be moved to the minimum logical address of the extracted entry. Thereafter, the table control unit 14 outputs a response to the table update request to the request arbitration unit 13.

  In addition, when the request arbitration unit 13 erases data, the table control unit 14 receives a table update request including the physical block address stored in the erase request from the request arbitration unit 13. Then, the table control unit 14 sets the minimum logical address of the entry corresponding to the designated physical block address as an initial value. Thereafter, the table control unit 14 outputs a response to the table update request to the request arbitration unit 13.

  Further, when receiving a table reference request, the table control unit 14 acquires the address conversion table 18 and the management information table 19 from the table storage unit 11. Then, the table control unit 14 outputs the acquired management information table 19 to the request arbitration unit 13. For example, when the table control unit 14 receives an instruction to cancel the association between the logical address and the data from the system executed by the information processing apparatus 1, the table control unit 14 corresponds to the target logical address in the address conversion table 18. The attached valid flag is updated to “0”.

  The device access control unit 15 executes device access to the NAND devices 7 a to 10 a in accordance with various requests from the request arbitration unit 13. For example, the device access control unit 15 receives a read request including a physical address from the request arbitration unit 13. In this case, the device access control unit 15 reads data stored in the page indicated by the physical address stored in the read request among the pages of the NAND devices 7a to 10a. Then, the device access control unit 15 outputs the read data to the request arbitration unit 13.

  For example, the device access control unit 15 receives a write request including a physical address and data to be written from the request arbitration unit 13. In this case, the device access control unit 15 stores the write target data in the physical page indicated by the physical address included in the write request. Thereafter, the device access control unit 15 outputs a response to the effect that the data writing has been completed to the request arbitration unit 13.

  For example, the device access control unit 15 receives an update request including an update source physical address, an update destination physical address, and data to be written from the request arbitration unit 13. In this case, the device access control unit 15 reads the data of the physical page indicated by the update source physical address. Subsequently, the device access control unit 15 updates the read data to data included in the update request. Then, the device access control unit 15 stores the updated data in the physical page indicated by the update destination physical address. Thereafter, the device access control unit 15 outputs a response to the effect that the data writing has been completed to the request arbitration unit 13.

  Further, the device access control unit 15 receives a movement request including the movement source physical address and the movement destination physical address from the request arbitration unit 13. In this case, the device access control unit 15 reads data from the physical page indicated by the source physical address, and stores the read data in the physical page indicated by the destination physical address. Thereafter, the device access control unit 15 outputs a response to the effect that the data movement has been completed to the request arbitration unit 13.

  Further, the device access control unit 15 receives from the request arbitration unit 13 an erasure request including a physical block address indicating a physical block that is a data erasure target. In this case, the device access control unit 15 erases the data stored in the physical block indicated by the physical block address included in the erase request, and outputs a response to the request arbitration unit 13 that the data erase is complete.

  The cyclic reference control unit 16 executes cyclic reference control at a predetermined timing. For example, the cyclic reference control unit 16 executes the cyclic reference control in response to a predetermined time interval, a predetermined time, or an instruction of an application program executed by the information processing apparatus 1.

  Hereinafter, the processing content of the cyclic reference control executed by the cyclic reference control unit 16 will be described. The cyclic reference control unit 16 includes a logical address selection unit 161, a physical address acquisition unit 162, and a determination unit 163.

  The logical address selection unit 161 outputs a request for referring to the address conversion table 18 and the management information table 19 to the request arbitration unit 13. Then, the logical address selection unit 161 receives the address conversion table 18 and the management information table 19 from the request arbitration unit 13.

  Next, the logical address selection unit 161 specifies one physical block whose effective page number is smaller than the threshold from the management information table 19. Next, the logical address selection unit 161 acquires the minimum logical address in the identified physical block. Then, the logical address selection unit 161 sets a search pointer to the minimum logical address. Thereafter, the logical address selection unit 161 outputs the minimum logical address to the physical address acquisition unit 162.

  Thereafter, when the logical address selection unit 161 receives an instruction to select the next logical address from the determination unit 163, the logical address selection unit 161 increments the search pointer by one and newly sets a logical address having the next largest address as a target of the movement determination process. Select Then, the logical address selection unit 161 outputs the selected logical address to the physical address acquisition unit 162. That is, the logical address selection unit 161 selects the logical addresses one by one in the order of increasing addresses with the minimum logical address as the search start address.

  The physical address acquisition unit 162 acquires a logical address from the logical address selection unit 161. Then, the physical address acquisition unit 162 refers to the address conversion table 18 and acquires a physical address associated with the selected logical address. Then, the physical address acquisition unit 162 outputs the acquired physical address to the determination unit 163.

  The determination unit 163 acquires a physical address from the physical address acquisition unit 162. Then, the determination unit 163 determines whether or not the page indicated by the acquired physical address is included in the specified physical block.

  When the acquired physical address is not included in the physical block address of the specified physical block, the determination unit 163 instructs the logical address selection unit 161 to select the next logical address.

  On the other hand, when the page having the acquired physical address is included in the specified physical block, the determination unit 163 determines whether the valid flag of the address conversion table 18 corresponding to the acquired physical address is “1”. Confirm whether or not. When the valid flag is “0”, the determination unit 163 instructs the logical address selection unit to select the next logical address.

  On the other hand, when the valid flag is “1”, the determination unit 163 outputs a set of the acquired physical address and the selected logical address to the data movement control unit 17. When the data movement is completed, the determination unit 163 determines whether there is still a valid page in the acquired physical block. For example, the determination unit 163 decrements 1 from the number of valid pages of the acquired physical block in the management information table 19 when the data is moved, and when the number of valid pages becomes 0, the valid page It is determined that is gone.

  If there is still a valid page, the determination unit 163 instructs the logical address selection unit to select the next logical address.

  When it is determined that there is no valid page, that is, the physical block is empty due to data movement, the determination unit 163 sets the acquired physical address, the selected logical address, and the last flag indicating that the block is empty. The set is output to the data movement control unit 17.

  The cyclic reference control unit 16 moves the data in the selected physical block and deletes the block to create a free capacity, and then determines whether a free capacity equal to or greater than a predetermined threshold value has been secured. If free space equal to or greater than the threshold value cannot be secured, the cyclic reference control unit 16 newly selects a physical block and repeats the above processing. When a free space equal to or greater than a predetermined threshold value can be secured, the cyclic reference control unit 16 ends the garbage collection process.

  The data movement control unit 17 performs data movement. Specifically, the data movement control unit 17 receives a set of a logical address and a physical address or a set of a logical address, a physical address, and a last flag from the cyclic reference control unit 16.

  When the data movement control unit 17 receives a combination of a logical address and a physical address from the determination unit 163 of the cyclic reference control unit 16, the data movement control unit 17 sets the physical address included in the received group as a movement source physical address. Then, the data movement control unit 17 outputs a movement request including the movement source physical address and the logical address included in the received set to the request arbitration unit 13. Thereafter, when receiving a response from the request arbitration unit 13 that the data movement has been completed, the data movement control unit 17 ends the data movement process of the physical page indicated by the physical address included in the received set.

  On the other hand, when the data movement control unit 17 receives the set of the logical address, the physical address, and the last flag from the determination unit 163 of the cyclic reference control unit 16, the physical address included in the received set is used as the movement source physical address. . Then, the data movement control unit 17 outputs a movement request including the movement source physical address and the logical address included in the received set to the request arbitration unit 13. Thereafter, when receiving a response indicating that the data movement is completed, the data movement control unit 17 outputs an erasure request including the physical block address included in the received set to the request arbitration unit 13. Then, when receiving a response from the request arbitration unit 13 that the data erasure is completed, the data movement control unit 17 ends the data movement process of the physical page indicated by the physical address included in the received set.

  For example, the data movement control unit 17 receives a set of the logical address “L0001”, the physical address “P0032”, and the last flag from the determination unit 163 of the cyclic reference control unit 16. In this case, the data movement control unit 17 outputs a movement request including the movement source physical address “P0032” and the logical address “L0001” to the request arbitration unit 13. When the data movement control unit 17 receives a response indicating that the data movement has been completed, the data movement control unit 17 outputs a request to erase the physical block address including the physical address “P0032” to the request arbitration unit 13. As a result, the NAND controller 6a erases the data of the physical block indicated by the physical block address including the physical address “P0032” to make a new spare block.

  For example, the requester interface unit 12, the request arbitration unit 13, the table control unit 14, the device access control unit 15, the cyclic reference control unit 16, and the data movement control unit 17 are electronic circuits. Here, as an example of the electronic circuit, an integrated circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA), a central processing unit (CPU), a micro processing unit (MPU), or the like is applied.

  The table storage unit 11 is a storage device such as a semiconductor memory element such as a RAM (Random Access Memory) and a flash memory.

  Next, processing executed by the NAND controller 6a according to the present embodiment will be described collectively with reference to FIG. FIG. 6 is a schematic diagram illustrating an example of a process executed by the NAND controller according to the first embodiment.

  For example, as illustrated in FIG. 6A, the NAND controller 6a refers to the management information table 19 and selects a physical block whose number of valid pages is equal to or less than a threshold value. Next, the NAND controller 6 a acquires the search start address of the selected physical block from the management information table 19.

  Next, as illustrated in FIG. 6B, the NAND controller 6 a acquires logical addresses sequentially from the search start address, and acquires a physical address associated with the acquired logical address from the address conversion table 18. . Then, the NAND controller 6a specifies a physical block address from the acquired physical address. Then, as illustrated in FIG. 6C, the NAND controller 6a refers to the management information table 19, and determines whether or not the identified physical block address is included in the address of the selected physical block. When the identified physical block address is included in the address of the selected physical block, the NAND controller 6a determines to move the data stored in the physical block.

  If the NAND controller 6a determines that the data of the physical block is to be moved, the NAND controller 6a performs data movement control as shown in (D) of FIG. Specifically, the NAND controller 6a uses the valid flag of the address conversion table 18 to identify the physical page in which valid data is stored, and sets the physical address indicating the identified physical page as the source physical address. Further, the NAND controller 6a acquires the physical address of the spare block from the management information table 19 as the movement destination physical address. Then, the NAND controller 6a performs data movement control using the selected logical address, movement source physical address, and movement destination physical address.

  Specifically, as illustrated in (E) of FIG. 6, the NAND controller 6 a performs device access control related to data movement using the movement source physical address and the movement destination physical address. As a result, as shown in FIG. 6F, the NAND controller 6a moves the data stored in the physical page indicated by the source physical address to the physical page indicated by the destination physical address. Then, the NAND controller 6a receives a response relating to the movement of data, as indicated by (G) and (H) in FIG.

  Then, the NAND controller 6a updates the management information table 19 in accordance with the movement of data, as indicated by (I) in FIG. Further, as shown in FIG. 6J, the NAND controller 6a updates the physical address associated with the selected logical address among the physical addresses stored in the address conversion table 18 to the movement destination physical address.

  That is, the NAND controller 6a does not determine whether to move data for each physical block, but determines whether to move data for each logical address. For this reason, the NAND controller 6a can update the address conversion table 18 without having an address reverse conversion table for converting the source physical address to the logical address. As a result, the NAND controller 6a can reduce the circuit scale. In addition, since the data movement determination is performed only for the logical address larger than the search start position, the NAND controller 6a can shorten the processing time of the data movement determination.

  Next, a flow of processing executed by the NAND controller 6a will be described with reference to FIG. FIG. 7 is a flowchart of processing executed by the NAND controller according to the first embodiment. The NAND controller 6a executes data movement control shown in FIG. 7 when a predetermined time has elapsed or when an instruction from software is received.

  The logical block selection unit 161 of the cyclic reference control unit 16 selects one physical block and searches the management information table 19 for the number of valid pages of the selected physical block (step S101).

  Then, the logical block selection unit 161 of the cyclic reference control unit 16 determines whether or not the number of valid pages of the selected physical block is less than a threshold value (step S102). When the number of valid pages is equal to or greater than the threshold (No at Step S102), the cyclic reference control unit 16 returns to Step S101.

  On the other hand, when the number of valid pages is less than the threshold value (Step S102: Yes), the logical block selection unit 161 of the cyclic reference control unit 16 acquires the minimum logical address of the selected physical block from the management information table 19. Then, the logical block selection unit 161 of the cyclic reference control unit 16 sets a search pointer at the acquired minimum logical address (step S103).

  Next, the physical block acquisition unit 162 of the cyclic reference control unit 16 acquires a physical address corresponding to the logical address indicated by the search pointer from the address conversion table 18, and uses the acquired physical address as a physical address to be moved. (Step S104).

  Next, the determination unit 163 of the cyclic reference control unit 16 determines whether or not a page having a physical address to be moved is included in the selected physical block (step S105). If not included in the selected physical block (No at Step S105), the logical block selection unit 161 of the cyclic reference control unit 16 increments the search pointer by one and updates the search pointer (Step S109).

  On the other hand, when included in the selected physical block (step S105: affirmative), the determination unit 163 of the cyclic reference control unit 16 performs address conversion to determine whether or not valid data is stored in the page having the movement determination target physical address. Determination is made from the table 18 (step S106). When valid data is not stored (step S106: No), the determination unit 163 of the cyclic reference control unit 16 increments the search pointer by one, updates the search pointer (step S109), and returns to step S104.

  On the other hand, when valid data is stored (step S106: Yes), the determination unit 163 of the cyclic reference control unit 16 sets the acquired physical address as a physical address to be moved. Then, the determination unit 163 of the cyclic reference control unit 16 outputs a set of a physical address to be moved and a logical address corresponding thereto to the data movement control unit 17. The data movement control unit 17 outputs a data movement request to the request arbitration unit 13 and moves the data from the physical address to be moved. Further, the table control unit 14 changes the physical address associated with the logical address of the address conversion table 18 and updates the address conversion table 18. Further, the determination unit 163 of the cyclic reference control unit 16 updates the management information table 19 by reducing the number of valid pages of the selected physical block in the management information table 19 by 1 (step S107).

  Next, the determination unit 163 of the cyclic reference control unit 16 determines whether or not the number of valid pages of the selected physical block has become 0 (step S108). When the number of valid pages is not 0 (No at Step S108), the logical block selection unit 161 of the cyclic reference control unit 16 increments the search pointer by 1 and updates the search pointer (Step S109).

  On the other hand, when the number of valid pages is 0 (step S108: Yes), the determination unit 163 of the cyclic reference control unit 16 outputs a last flag to the data movement control unit 17. The data movement control unit 17 transmits a physical block erase command including the physical address to be moved to the request arbitration unit 13 to erase the physical block. Further, the cyclic reference control unit 16 sets the minimum logical address corresponding to the selected physical block in the management information table 19 to an initial value and updates the management information table 19 (step S110).

  Thereafter, the cyclic reference control unit 16 determines whether or not the free space is equal to or less than a threshold value (step S111). When the free space is equal to or less than the threshold (step S111: Yes), the cyclic reference control unit 16 returns to step S101. On the other hand, when the free space is larger than the threshold (No at Step S111), the NAND controller 6a ends the data movement control process.

  Next, update processing of the minimum logical address of the management information table 19 according to the present embodiment will be described with reference to FIG. FIG. 8 is a flowchart of the update process of the minimum logical address of the management information table according to the first embodiment.

  The table control unit 14 determines whether or not the request arbitration unit 13 has received a write command from the requester interface unit 12 (step S201). When the write command has not been received (No at Step S201), the table control unit 14 ends the update process of the minimum logical address.

  On the other hand, when a write command is received (step S201: Yes), the table control unit 14 searches the management information table 19 for a physical block including a physical address designated as a data storage destination by the write command ( Step S202).

  Next, the table control unit 14 acquires the minimum logical address of the searched physical block from the management information table 19 (step S203).

  Then, the table control unit 14 determines whether or not the data storage destination logical address is less than the acquired minimum logical address (step S204). When the logical address of the data storage destination is equal to or greater than the acquired minimum logical address (No at Step S204), the table control unit 14 ends the update process of the minimum logical address.

  On the other hand, when the logical address of the data storage destination is less than the acquired minimum logical address (step S204: Yes), the table control unit 14 sets the minimum logical address of the retrieved physical block as the logical address of the data storage destination. (Step S205).

  As described above, when performing the garbage collection, the information processing apparatus according to the present embodiment searches the physical address in the order in which the logical address increases, with the minimum logical address of the target physical block as the search start position, It is determined whether or not to perform data movement. Thereby, garbage collection can be performed without using a reverse lookup table for retrieving a logical address from a physical address, and the circuit scale of the NAND controller can be suppressed. Further, since the data movement determination can be omitted for a logical address smaller than the minimum logical address, the garbage collection time can be shortened and the access performance can be improved.

  Next, a NAND controller according to the second embodiment will be described. The NAND controller according to the present embodiment is different from the first embodiment in that the maximum logical address is used as the search start position. Therefore, in the following, setting of the maximum logical address and determination of data movement when the maximum logical address is set as the search start position will be mainly described. A block diagram of the NAND controller 6a according to this embodiment is also shown in FIG. In the following description, description of each part having the same function as in the first embodiment is omitted.

  FIG. 9 is a diagram illustrating an example of a management information table according to the second embodiment. As shown in FIG. 9, the management information table 19 stores a physical block address, the number of valid pages, and a maximum logical address in association with each other.

  The maximum logical address is the maximum address among the logical addresses corresponding to each physical address of the page included in the block indicated by the physical block address.

  For example, in the example shown in FIG. 9, the management information table 19 stores the physical block address “B00”, the number of valid pages “11”, and the minimum logical address “Lff0e” in association with each other. That is, the management information table 19 indicates that 11 pages are valid among the physical pages included in the physical block indicated by the physical block address “B00”. Further, the management information table 19 indicates that the maximum logical address among the logical addresses corresponding to the physical block address “B00” is “Lff0e”.

  Furthermore, in the example illustrated in FIG. 9, the physical block address “B01” in the management information table 19 has no valid page and no maximum logical address is set. Here, when the maximum logical address is not set, in this embodiment, “Lffff”, which is the largest logical address among all the logical addresses, is set as an initial value.

  When the request arbitration unit 13 writes new data, the table control unit 14 extracts an entry associated with the physical block address indicated by the physical address acquired from the table update request from the management information table 19. Then, the table control unit 14 increases the number of valid pages of the extracted entry by one. In addition, the table control unit 14 acquires the maximum logical address of the extracted entry from the management information table 19. Then, the table control unit 14 determines whether or not the logical address of the data to be written is larger than the acquired maximum logical address. When the logical address of the data to be written is larger than the acquired maximum logical address, the table control unit 14 writes the logical address of the data to be written to the maximum logical address of the extracted entry.

  Similarly, the table control unit 14 extracts an entry associated with the update destination physical block address from the management information table 19 when the request arbitration unit 13 updates data. Then, the table control unit 14 increases the number of valid pages of the extracted entry by one. In addition, the table control unit 14 acquires the maximum logical address of the extracted entry from the management information table 19. Then, the table control unit 14 determines whether or not the logical address of the data to be updated is larger than the acquired maximum logical address. When the logical address of the data to be updated is larger than the acquired maximum logical address, the table control unit 14 writes the logical address of the data to be updated to the maximum logical address of the extracted entry.

  Further, when the request arbitration unit 13 moves data, the table control unit 14 extracts an entry associated with the movement destination physical block address from the management information table 19. Then, the table control unit 14 increases the number of valid pages of the extracted entry by one. In addition, the table control unit 14 acquires the maximum logical address of the extracted entry from the management information table 19. Then, the table control unit 14 determines whether or not the logical address of the data to be moved is larger than the acquired maximum logical address. When the logical address of the data to be moved is larger than the acquired maximum logical address, the table control unit 14 writes the logical address of the data to be moved to the maximum logical address of the extracted entry.

  The logical block selection unit 161 of the cyclic reference control unit 16 outputs a reference request for the address conversion table 18 and the management information table 19 to the request arbitration unit 13. The logical block selection unit 161 receives the address conversion table 18 and the management information table 19 from the request arbitration unit 13.

  Then, the logical block selection unit 161 specifies one physical block whose number of valid pages is smaller than the threshold from the management information table 19. Next, the logical block selection unit 161 acquires the maximum logical address in the identified physical block. Then, the logical address selection unit 161 sets a search pointer at the maximum logical address. Thereafter, the logical address selection unit 161 outputs the maximum logical address to the physical address acquisition unit 162.

  Thereafter, when the logical address selection unit 161 receives an instruction to acquire the next logical address from the determination unit 163, the logical address selection unit 161 decreases the search pointer by one and newly sets a logical address having the next smaller address as a target of the movement determination process. Select Then, the logical address selection unit 161 outputs the selected logical address to the physical address acquisition unit 162. That is, the logical address selection unit 161 selects the logical addresses one by one in the order of decreasing addresses with the maximum logical address as the search start address. This maximum logical address corresponds to an example of “search start position”.

  The physical block acquisition unit 162 and the determination unit 161 of the cyclic reference control unit 16 operate in the same manner as in the first embodiment.

  Next, a flow of processing executed by the NAND controller 6a will be described with reference to FIG. FIG. 10 is a flowchart of a process executed by the NAND controller according to the second embodiment. The NAND controller 6a executes the data movement control shown in FIG. 10 when a predetermined time has elapsed or when an instruction from the software is received.

  The logical block selection unit 161 of the cyclic reference control unit 16 selects one physical block and searches the management information table 19 for the number of valid pages of the selected physical block (step S301).

  Then, the logical block selection unit 161 of the cyclic reference control unit 16 determines whether or not the number of valid pages of the selected physical block is less than a threshold value (step S302). If the number of valid pages is equal to or greater than the threshold (No at Step S302), the logical block selection unit 161 of the cyclic reference control unit 16 returns to Step S301.

  On the other hand, when the number of valid pages is less than the threshold (step S302: Yes), the logical block selection unit 161 of the cyclic reference control unit 16 acquires the maximum logical address of the selected physical block from the management information table 19. Then, the logical block selection unit 161 of the cyclic reference control unit 16 sets a search pointer at the acquired maximum logical address (step S303).

  Next, the physical block acquisition unit 162 of the cyclic reference control unit 16 acquires a physical address corresponding to the logical address indicated by the search pointer from the address conversion table 18, and uses the acquired physical address as a physical address to be moved. (Step S304).

  Next, the determination unit 163 of the cyclic reference control unit 16 determines whether or not a page having a movement determination target physical address is included in the selected physical block (step S305). If not included in the selected physical block (step S305: No), the logical block selection unit 161 of the cyclic reference control unit 16 decrements the search pointer by one and updates the search pointer (step S309), and step S304. Return to.

  On the other hand, when included in the selected physical block (step S305: affirmative), the determination unit 163 of the cyclic reference control unit 16 performs address conversion to determine whether or not valid data is stored in the page having the movement determination target physical address. The determination is made from the table 18 (step S306). When valid data is not stored (No at Step S306), the logical block selection unit 161 of the cyclic reference control unit 16 decrements the search pointer by one and updates the search pointer (Step S309).

  On the other hand, when valid data is stored (step S306: affirmative), the determination unit 163 of the cyclic reference control unit 16 sets the acquired physical address as a physical address to be moved. Then, the determination unit 163 of the cyclic reference control unit 16 outputs a set of a physical address to be moved and a logical address corresponding thereto to the data movement control unit 17. The data movement control unit 17 outputs a data movement request to the request arbitration unit 13 and moves the data from the physical address to be moved. Further, the table control unit 14 changes the physical address associated with the logical address of the address conversion table 18 and updates the address conversion table 18. Further, the cyclic reference control unit 16 updates the management information table 19 by reducing the number of valid pages of the selected physical block in the management information table 19 by one (step S307).

  Next, the determination unit 163 of the cyclic reference control unit 16 determines whether or not the number of valid pages of the selected physical block has become 0 (step S308). When the number of valid pages is not 0 (No at Step S308), the selection unit 161 of the cyclic reference control unit 16 decrements the search pointer by one and updates the search pointer (Step S309).

  On the other hand, when the number of valid pages is 0 (step S308: Yes), the determination unit 163 of the cyclic reference control unit 16 outputs a last flag to the data movement control unit 17. The data movement control unit 17 transmits a physical block erase command including the physical address to be moved to the request arbitration unit 13 to erase the physical block. The cyclic reference control unit 16 sets the maximum logical address corresponding to the selected physical block in the management information table 19 to an initial value (for example, 0xffff), and updates the management information table 19 (step S310).

  Thereafter, the cyclic reference control unit 16 determines whether or not the free space is equal to or less than the threshold (step S311). When the free space is equal to or smaller than the threshold (step S311: affirmative), the cyclic reference control unit 16 returns to step S301. On the other hand, when the free space is larger than the threshold (No at Step S311), the NAND controller 6a ends the data movement control process.

  Next, update processing of the maximum logical address of the management information table 19 according to the present embodiment will be described with reference to FIG. FIG. 11 is a flowchart of the update process of the maximum logical address of the management information table according to the second embodiment.

  The table control unit 14 determines whether or not the request arbitration unit 13 has received a write command from the requester interface unit 12 (step S401). When the write command has not been received (No at Step S401), the table control unit 14 ends the update process of the maximum logical address.

  On the other hand, when a write command is received (step S401: Yes), the table control unit 14 physically stores data based on the logical address designated as the data storage destination by the write command. A physical block including the address is searched from the management information table 19 (step S402).

  Next, the table control unit 14 acquires the maximum logical address of the searched physical block from the management information table 19 (step S403).

  Then, the table control unit 14 determines whether or not the logical address of the data storage destination is larger than the acquired maximum logical address (step S404). If the logical address of the data storage destination is less than or equal to the acquired maximum logical address (No at Step S404), the table control unit 14 ends the update process of the maximum logical address.

  On the other hand, when the logical address of the data storage destination is larger than the acquired maximum logical address (step S404: Yes), the table control unit 14 sets the maximum logical address of the retrieved physical block as the logical address of the data storage destination. (Step S405).

  As described above, when performing data movement such as garbage collection, the information processing apparatus according to the present embodiment uses the maximum logical address of the target physical block as the search start position, and the physical addresses in the order of increasing logical addresses. To determine whether to perform data movement. Also in this case, since the data movement determination can be omitted for a logical address larger than the maximum logical address, the data movement time can be shortened and the access performance can be improved.

  Further, in each of the embodiments described above, the physical block to which data movement is performed is identified and it is determined whether or not the logical address corresponds to the physical address of the page included in the physical block. Not limited to this. For example, after selecting a logical address from the management table and specifying a corresponding physical address, it is determined whether or not a physical block including a page having the physical address is a physical block to be moved, and data movement processing is performed. You may go.

  FIG. 12 is a diagram of an example of a NAND controller that executes a control program. As illustrated in FIG. 12, the NAND controller 6 e includes a CPU 40 and a device access control unit 15. The CPU 40 is connected to the memory device 11a. Note that the memory device 11a may be a memory built in the NAND controller 6e.

  The memory device 11a stores an address conversion table 18 and a management information table 19 in advance. Here, the control program 30 functions as follows when the CPU 40 reads out, expands and executes the control program 30. That is, the control program 30 causes the CPU 40 to operate as the table control unit 31, the request arbitration unit 32, the cyclic reference control unit 33, and the data movement control unit 34. Here, the table control unit 31, the request arbitration unit 32, the cyclic reference control unit 33, and the data movement control unit 34 are the table control unit 14, the request arbitration unit 13, the cyclic reference control unit 16, and the data movement control shown in FIG. The same function as the unit 17 is exhibited.

  Note that the NAND controller 6e may execute the control program 30 using an arithmetic device such as an MPU or FPGA instead of the CPU. Further, the control program 30 may be stored in, for example, the memory device 11a or the NAND devices 7a to 10a, or may be executed by the CPU 40 by other methods. For example, each program is stored in a “portable physical medium” such as a flexible disk, so-called FD (Flexible Disk), CD (Compact Disk) -ROM, DVD (Digital Versatile Disk), magneto-optical disk, or IC card.

  Then, the NAND controller 6e may acquire and execute each program from these portable physical media via each CPU 40. Further, each program stored in another computer or a server device may be acquired and executed via a public line, the Internet, a LAN (Local Area Network), a WAN (Wide Area Network), or the like.

1 Information processing device 2a, 2b Memory 3a, 3b, 40 CPU
4 I / O hub 5a, 5b SSD
6a, 6b, 6e NAND controllers 7a-10a, 7b-10b NAND devices 11 Table storage unit 12 Requester interface unit 13, 32 Request arbitration unit 14, 31 Table control unit 15 Device access control unit 16, 33 Cyclic reference control unit 17, 34 Data Movement Control Unit 18 Address Conversion Table 19 Management Information Table 30 Control Program 161 Logical Address Selection Unit 162 Physical Address Acquisition Unit 163 Determination Unit

Claims (8)

A storage device having a plurality of storage areas;
For each block including a plurality of storage areas, a start position setting unit that sets, as a search start position, a logical address that satisfies a predetermined condition among logical addresses corresponding to physical addresses that identify a storage area included in each block;
A selection unit that selects a logical address in a predetermined order from the search start position of the conversion table representing the correspondence between the logical address and the physical address;
An acquisition unit that acquires a physical address associated with the logical address selected by the selection unit from the conversion table;
A determination unit that determines whether or not to move data stored in a storage area indicated by the physical address acquired by the acquisition unit using a predetermined condition;
When the determination unit determines to move the data, a moving unit that moves the data stored in the storage area indicated by the physical address acquired by the acquisition unit to another storage area;
An update unit that updates a physical address associated with the logical address selected by the selection unit among physical addresses stored in the conversion table to a physical address indicating the other storage area; Information processing apparatus. The start position setting unit sets the minimum logical address among the logical addresses of the storage area corresponding to the physical address of each block as a search start position,
The information processing apparatus according to claim 1, wherein the selection unit selects logical addresses in order of increasing. The start position setting unit sets the maximum logical address among the logical addresses of the storage area corresponding to the physical address of each block as a search start position,
The information processing apparatus according to claim 1, wherein the selection unit selects logical addresses in ascending order.   The information processing apparatus according to claim 1, wherein the determination unit determines to move data when the number of the storage areas storing valid data in the block is less than a threshold value. The selection unit selects a block in which the storage area storing valid data is equal to or less than a threshold, selects a logical address in a predetermined order from a search start position of the selected block,
The information processing apparatus according to claim 1, wherein the determination unit determines to move data when a physical address is included in a block acquired by the selection unit. For each block including a plurality of storage areas, a start position setting unit that sets, as a search start position, a logical address that satisfies a predetermined condition among logical addresses corresponding to a physical address that identifies a storage area included in each block;
A selection unit that selects a logical address in a predetermined order from the search start position of the conversion table representing the correspondence between the logical address and the physical address;
An acquisition unit that acquires a physical address associated with the logical address selected by the selection unit from the conversion table;
A determination unit that determines whether or not to move data stored in a storage area indicated by the physical address acquired by the acquisition unit using a predetermined condition;
When the determination unit determines to move the data, a moving unit that moves the data stored in the storage area indicated by the physical address acquired by the acquisition unit to another storage area;
An update unit that updates a physical address associated with the logical address selected by the selection unit among physical addresses stored in the conversion table to a physical address indicating the other storage area; Control circuit. For each block including a plurality of storage areas, set a logical address that satisfies a predetermined condition as a search start position among logical addresses corresponding to a physical address for identifying a storage area included in each block,
Selecting a logical address in a predetermined order from the search start position of the conversion table representing the correspondence between the logical address and the physical address;
Obtaining a physical address associated with the selected logical address from the conversion table;
Using predetermined conditions, determine whether to move the data stored in the storage area indicated by the acquired physical address,
If it is determined that the data is to be moved, the data stored in the storage area indicated by the acquired physical address is moved to another storage area,
A control program for causing a computer to execute a process of updating a physical address associated with a selected logical address among physical addresses stored in the conversion table to a physical address indicating the other storage area . For each block including a plurality of storage areas, set a logical address that satisfies a predetermined condition as a search start position among logical addresses corresponding to a physical address for identifying a storage area included in each block,
Selecting a logical address in a predetermined order from the search start position of the conversion table representing the correspondence between the logical address and the physical address;
Obtaining a physical address associated with the selected logical address from the conversion table;
Using predetermined conditions, determine whether to move the data stored in the storage area indicated by the acquired physical address,
If it is determined that the data is to be moved, the data stored in the storage area indicated by the acquired physical address is moved to another storage area,
A control method comprising: updating a physical address associated with a selected logical address among physical addresses stored in the conversion table to a physical address indicating the other storage area.

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