KR100816820B1 - Apparatus and method for managing buffer linked with flash memory - Google Patents

Abstract

A device and a method for managing a buffer linked with a flash memory are provided to improve a data storage ratio, performance, and lifetime of a NAND flash memory by storing data to the NAND flash memory without an empty slot in a page of the NAND flash memory. A buffer(210) comprises a general area storing target data to be written to a NAND flash memory and page unit data read from the NAND flash memory, and an exclusive area storing managed data selected among the page unit data read from the NAND flash memory. A buffer manager(220) writes the target data to a storage area corresponding to an empty slot of a page comprising the managed data stored in the exclusive area, and removes the managed data from the exclusive area when the number of empty slots of the page comprising the managed data is smaller than a first reference number. A managed data selector(230) selects the data having the number of empty slots higher than a second reference number among the page unit data read from the NAND flash memory.

Description

Apparatus and method for managing buffer linked with flash memory}

1 illustrates a slot page structure of a flash memory;

2 is a block diagram showing the configuration of a preferred embodiment of a buffer management apparatus interoperating with a flash memory according to the present invention;

3 is a view showing a preferred embodiment of the buffer unit of the buffer management device interlocked with the flash memory according to the present invention;

4 is a flowchart illustrating a process of performing a preferred embodiment of a buffer management method interoperating with a flash memory according to the present invention;

5 is a flowchart illustrating a process of performing another preferred embodiment of a buffer management method interoperating with a flash memory according to the present invention.

The present invention relates to an apparatus and method for managing a buffer interoperating with a flash memory, and more particularly, to an apparatus and method for performing a record write operation to a NAND flash memory.

Flash memory is composed of consecutive blocks of the same size, and one block is composed of consecutive pages of the same size. There are three operations that can be performed in flash memory: read, write and erase. Read and write operations are performed in units of pages, and erase operations are performed in units of blocks. At this time, the write operation takes more execution time than the read operation, and causes an erase operation that requires more execution time than the write operation. Therefore, reducing the number of write operations improves the overall performance of the flash memory.

Unlike hard disks, flash memory has unique characteristics. First, pages targeted for write operations must be erased in advance. Therefore, in-place update is impossible, and when a page is modified, a new physical page must be allocated to perform a write operation. Second, the number of erase operations that can be performed in the flash memory is generally limited to 100,000 or less. Therefore, the more write operations are performed, the more erase operations are performed, which shortens the life of the flash memory.

1 illustrates a slot page structure of a flash memory.

Referring to FIG. 1, the slot page 100 includes a plurality of slots 110 to 180 and one metadata 190. The slot page 100 is a representative structure for storing a record which is a unit constituting data. Slots 110 to 180 are logical structures in which slot pages 100 are divided into several equal sizes, and one record is stored in one slot. The size of the slots 110 to 180 depends on the size of the record to be stored, and the number of slots present in one slot page 100 depends on the size of the slot. In the metadata area 190, information necessary for managing the slot page 100 and empty space list configuration information, which is information on an empty slot, are recorded.

Read and write operations in flash memory are performed through the buffer. A buffer is a memory that compensates for the speed between a very fast central processor and a very slow auxiliary memory. Some areas of computer main memory are used as buffers, or memory added separately to flash memory storage is used as a buffer. After the page of the flash memory on which the write operation is to be performed is loaded into the buffer, the record to be written to the flash memory is stored in the buffer. Later, when the buffer becomes full, certain pages are replaced to free up space. If there is a change in the contents of the replaced page, the changed contents are stored in a new page of the flash memory through a write operation.

Existing buffer management techniques for determining pages to be replaced include first-in, first-out (FIFO), least recently used (LRU), least frequently used (LFU), and most recently used (MFU). These techniques use the time of buffer storage, the elapsed time after buffer storage, and the number of times of referencing after storage to determine replacement pages among memory buffer pages. The FIFO technique first replaces the first page loaded in the buffer. The LRU technique first replaces the oldest page after a write operation. The LFU technique preferentially replaces pages with the least number of write operations, and the MFU technique preferentially replaces pages with the highest number of write operations.

As described above, the existing buffer management scheme selects a page to be replaced without considering the number of empty slots of pages loaded in the buffer. As a result, a large number of pages with many empty slots exist in the flash memory, thereby reducing storage efficiency of the flash memory. In addition, the write insertion time is delayed because more write operations are induced than storing records without empty slots in a page of flash memory. And many write operations cause frequent erase operations, which shortens the life of flash memory. As such, there is a problem in the conventional buffer replacement technique that degrades the flash memory performance and shortens the lifespan.

An object of the present invention is to provide a flash memory management apparatus and method for improving the data storage rate and performance of a flash memory and extending the life of the flash memory.

Another technical problem to be achieved by the present invention is a computer-readable recording medium having recorded thereon a program for executing a flash memory management method that can improve the data storage rate and performance of a flash memory and extend the life of the flash memory. To provide.

In order to achieve the above technical problem, a buffer management apparatus interoperating with a flash memory according to the present invention includes a general-purpose area in which data to be written in a flash memory and data in units of pages read from the flash memory are stored; A buffer unit including a dedicated area for storing selected management target data among data of a page unit read from a flash memory; The recording target data is recorded in a storage area corresponding to an empty slot of a page composed of management target data stored in a dedicated area of the buffer unit, and the number of empty slots of the page composed of the management target data is removed. A buffer manager which removes the management target data from the dedicated area if less; And a memory driver configured to store the management object data removed from the dedicated area in the flash memory.

In addition, in order to achieve the above technical problem, the buffer management method interoperating with the flash memory according to the present invention is a buffer memory comprising a general-purpose area and a dedicated area for the management target data selected from data consisting of page units read from the flash memory. A data storage step of storing in a dedicated area; A data recording step of recording the recording target data to be recorded in the flash memory into an area corresponding to an empty slot of a page composed of the management target data in a dedicated region of the buffer memory; A data removing step of removing from the dedicated area of the buffer memory if the number of empty slots of the page composed of the management target data is less than or equal to the reference number for removal; And a flash memory access step of storing management target data removed from the dedicated area of the buffer memory in the flash memory.

As a result, data may be stored in each page of the flash memory at a high storage rate, and as the storage rate is increased, the performance of the flash memory may be improved and its life may be extended.

Hereinafter, exemplary embodiments of a buffer management apparatus and method interoperating with a flash memory according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing the configuration of a preferred embodiment of a buffer management apparatus interoperating with a flash memory according to the present invention.

Referring to FIG. 2, a buffer management apparatus interoperating with a flash memory according to the present invention includes a buffer unit 210, a buffer manager 220, a management target data selector 230, and a memory driver 240.

The buffer unit 210 stores a general area in which recording target data to be written in the flash memory and data in page units read from the flash memory are stored, and a dedicated area in which selected management target data is stored among page unit data read from the flash memory. Is done. In addition, the buffer unit 210 temporarily stores write data and page data in units of pages read from the write target page in order to perform write and erase operations in the flash memory. Before the write and delete operations are performed on the pages of the flash memory, writing and deleting of the page data stored in the buffer unit 210 are performed first.

3 is a view showing a preferred embodiment of the buffer unit according to the present invention. Referring to FIG. 3, in the general area 310, page data composed of recording target data to be written to the flash memory and page units read from the flash memory are recorded. The page data is data including data stored in the slot and metadata area of the slot page of the flash memory. Therefore, the page data includes not only data stored in each slot of the slot page, but also information necessary for managing the slot page and information on an empty space list which is information on empty slots. The number of page data stored in the general-purpose area 310 depends on the size of the general-purpose area 310. The size of the general-purpose area 310 is determined within the allowable range of the memory of the management device interlocked with the flash memory according to the present invention. For example, the size of the general-purpose area 310 is set to a size capable of storing 64 page data and 128 KByte recording target data.

The dedicated area 320 stores management target data selected from data of a page unit read from the flash memory. Here, the management target data is data having the same contents as the page data. The number of management target data stored in the dedicated area 320 depends on the size of the dedicated area. Basically, the size of the dedicated area 320 may be set to the size of one piece of management target data, and may be set to a size in which a plurality of pieces of management target data may be stored if necessary.

The buffer manager 220 stores page data read from the flash memory in the buffer 210, writes and deletes page data stored in the buffer 210, and writes page data from the buffer 210. Remove

In relation to a storage operation of the data read from the flash memory in the buffer unit 210, the buffer manager 220 stores the read page data in the general-purpose area 310 of the buffer unit 210. If there is no space to store the page data of the page read in the general area 310, the buffer manager 220 stores the page data in the empty space obtained by removing the previously stored page data from the general area 310. . The operation of selecting a page to be removed from the general area 310 among the previously stored page data may include first-in, first-out (FIFO), least recently used (LRU), least frequently used (LFU), and most recently MFU (MFU). It is performed by an existing buffer management algorithm such as Used).

In addition, the buffer manager 220 records the recording target data in a storage area corresponding to an empty slot of a page composed of the management target data stored in the dedicated area 320 of the buffer 210. The recording target data is data constituting a file such as data stored in a slot of management target data or data constituting a new file. The buffer manager 220 records the recording target data in a storage area corresponding to an empty slot of the page data read from the page of the flash memory in which the file composed of the recording target data is stored. The page data is page data stored in the general area 310 or management target data stored in the dedicated area 320. In this case, in order to further increase the storage rate of the flash memory, the buffer manager 220 may store the data to be recorded only in the dedicated area 320.

In addition, the buffer manager 220 removes the management target data from the dedicated area when the number of empty slots of the page configured as the management target data is equal to or smaller than the reference number for removal. The reference number for removal is set according to the intended use of the flash memory. When the performance of the flash memory is important, the removal reference number is set high, and when the storage rate is important, the removal reference number is set low. For example, when the reference number for removal is set to 0, the buffer management unit 220 removes the management target data from the buffer unit 210 when all empty slots of the page corresponding to the management target data are erased.

The management target data selector 230 selects management target data from the page data of the page searched by the memory driver 240. At this time, the management target data selector 230 selects data whose page count is equal to or larger than the reference number of the selected data among the page unit data read from the flash memory as the management target data. The reference number for selection, which is a management target data selection criterion, is set in consideration of the storage rate of the flash memory. If the standard number for selection is set high, a situation may occur in which the data to be selected does not exist. If the standard number for selection is set low, the storage rate may not be greatly improved. The selected management target data is stored in the dedicated area 320. The operation of storing the management target data in the dedicated area 320 may be directly performed by the management target data selector 230, or alternatively, may be performed by the buffer manager 220.

On the other hand, the management target data selector 230 selects data whose number of empty slots is greater than or equal to the moving reference number from among page data stored in the general area 310 as management target data and moves the data to the dedicated area 320. At this time, if the page data constituting the same file as the recording target data is selected, the number of page data constituting the file can be reduced, and if the selection among the page data for write operations is selected, the data recording efficiency can be increased. When the data moves in the buffer unit 210, the management target data selecting unit 230 selects the page data having the largest number of empty slots among the page data stored in the general-purpose area 310 as the management target data. To 320). On the other hand, if the buffer management unit 220 removes the management target data from the general-purpose area 310 and an empty space occurs in the dedicated area 320, the management target data selection unit 230 stores the page stored in the general-purpose area 310. Select new target data from the data.

In addition, the management target data selector 230 selects the page data allocated from the flash memory when the page data to be transferred to the dedicated area 320 is not selected from the page data stored in the general area 310. It is selected as the management target data to be stored in 320). It is preferable that the reference number for the management target data is set according to the number of times of deletion and recording of the page data stored in the general reference area 310 for movement, and if necessary, the reference number for movement is set equal to the reference number for selection. Can be.

The management target data selector 230 operating as described above has a problem in that the number of empty slots of the page data stored in the general area 310 of the buffer 210 must be calculated every time. In this case, it is possible to reduce the operation execution time by identifying and managing the number of empty slots of page data in advance. To this end, the management target data selector 230 examines data in which the number of empty slots is greater than or equal to the management reference number among data composed of page units read from the flash memory. The reference number for management is set in consideration of the storage rate of the flash memory. If the reference number for management is set high, a situation may occur in which data to be selected does not exist. If the reference number for management is set low, many data are selected and management becomes difficult.

Based on the survey result of the page data, the management target data selector 230 generates a threshold list that is a list of address information indicating data whose number of empty slots is equal to or greater than the management reference number. Table 1 shows an example of a threshold list.

index address Empty slots One 07 20 2 08 17 3 02 15 4 0A 13 5 01 10

In Table 1, the value of the address field indicates the physical location of page data stored in the general area 310 in hexadecimal.

When the threshold list is generated and managed as described above, the management target data selector 230 selects page data at the first position (index 1) of the threshold list as the management target data. In this case, it is preferable that the threshold list is arranged based on the number of empty slots of the page data so that the page data having the largest number of empty slots is selected as the management target data.

The management target data selector 230 updates the threshold list when changing the page unit data stored in the general area 310 or when removing the data in the page unit from the general area 310. If the page data stored in the general-purpose area 310 is changed by the existing buffer management technique, it is necessary to reflect the changed situation in the threshold list. In order to reflect these changes in the threshold list, the management target data selector 230 updates the threshold list. In addition, when the threshold list is updated, the management target data selector 230 may also sort the threshold list based on the number of empty slots.

The memory driver 240 accesses the flash memory to read data or write data. When the read command, the write command, and the delete command for the flash memory are executed, the memory driver 240 searches the target page on which the command is to be executed by accessing the flash memory. For example, when the delete command is executed, the memory driver 240 searches the flash page for the slot page in which the file to which the data to be deleted belongs is recorded. At this time, the retrieved page is a page that constitutes a file to be executed.

In addition, the memory driver 240 stores page data or management target data removed from the buffer unit 210 in the flash memory. That is, the memory driver 240 stores the removed page data or management target data in the page of the flash memory in which each data is read. If a situation in which each data cannot be stored in a page of the read flash memory occurs, the memory driver 240 allocates a new page from the flash memory and stores the removed page data or management target data in the allocated new page. .

4 is a flowchart illustrating a preferred embodiment of a buffer management method interoperating with a flash memory according to the present invention.

Referring to FIG. 4, the memory driver 240 reads a work target page from the flash memory (S400). The management target data selector 230 selects data whose number of empty slots is greater than or equal to a reference number (for example, five) from among the read page unit data as management target data and selects the dedicated area of the buffer unit 210. In operation S410, it is stored in 320. The buffer manager 220 records the recording target data to be recorded in the flash memory in a storage area corresponding to an empty slot of the page including the management target data (S420). Next, when the number of empty slots of the page configured as the management target data becomes less than or equal to the reference number for removal, the buffer manager 220 removes the management target data from the dedicated area 320 (S430). At this time, it is preferable that the reference number for data removal is set to zero for efficient use and extended life of the flash memory. When the data is removed from the dedicated area 320 of the buffer unit 210 as described above, the management target data selecting unit 230 determines that the number of empty slots in the page unit data stored in the general area 310 is the reference number for moving (eg, For example, five or more pieces of data are selected as the management target data and moved to the dedicated area 320 (S440). The memory driver 230 stores the management target data removed from the dedicated area 320 in the flash memory (S450).

5 is a flowchart illustrating a process of performing another preferred embodiment of a buffer management method interoperating with a flash memory according to the present invention.

Referring to FIG. 5, the memory driver 240 reads a work command target page from the flash memory (S500). The management target data selector 230 generates a threshold list that is a list of address information indicating data whose number of empty slots is greater than or equal to the management reference number (for example, five) among the data configured in the unit of read pages ( S510). The generated threshold list is updated when the page data stored in the general area 310 of the buffer unit 210 is changed. The management target data selector 230 selects the management target data from the threshold list and stores the management target data in the dedicated area 320 of the buffer unit 210 (S520). In this case, it is preferable to select data having the largest number of empty slots as management target data. The buffer manager 220 records the recording target data to be recorded in the flash memory in a storage area corresponding to an empty slot of a page including the management target data (S530). Next, when the number of empty slots of the page configured as the management target data is less than or equal to the reference number for removal, the buffer manager 220 removes the management target data from the dedicated area 320 of the buffer unit 210 (S540). When data is removed from the dedicated area 320 of the buffer unit 210 as described above, the management target data selector 230 selects page data having a moving reference number or more from the threshold list as the management target data and stores the buffer 210. It is stored in the dedicated area 320 (S550). The memory driver 240 stores the management target data removed from the dedicated area 320 of the buffer 210 in the flash memory (S560).

The invention can also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

According to a buffer management apparatus and method interoperating with a flash memory according to the present invention, by storing data such that an empty slot does not exist in a page of the flash memory, the storage rate of the flash memory is increased and the number of times of write operations are performed is reduced. In addition, higher storage rates and fewer write operations improve flash memory performance and reduce the number of times of erase operations in the flash memory. As the number of times of erase operations is reduced, the life of the flash memory can be extended.

Claims (13)

A buffer unit including a general area for storing recording target data to be written to a flash memory and data in units of pages read from the flash memory, and a dedicated area for storing selected management target data among page units of data read from the flash memory. ; The recording target data is recorded in a storage area corresponding to an empty slot of a page composed of management target data stored in a dedicated area of the buffer unit, and the number of empty slots of the page composed of the management target data is the first reference number. A buffer manager which removes the management target data from the dedicated area if less; And And a memory driver for storing management target data removed from the dedicated area in the flash memory. The method of claim 1, And a management target data selector configured to select, as the management target data, data whose number of empty slots is equal to or greater than a second reference number from among the data in the page unit read out from the flash memory. . The method of claim 2, The management target data selecting unit selects data whose number of empty slots is greater than or equal to a third reference number from among page data stored in the general-purpose area when the management target data is removed from the dedicated area as the management target data. A buffer management device interlocked with the flash memory, characterized in that moved to. The method of claim 1, Investigate data having the number of empty slots equal to or greater than a fourth reference number among data read in the page unit, and generate a threshold list that is a list of address information indicating the data, and from the threshold list, the management target. And a management object data selection unit for selecting data. The method of claim 4, wherein The management target data selection unit updates the threshold list when the data in the page unit stored in the universal area is changed or when the data in the page unit is removed from the general area. Device. The method of claim 4, wherein And the management target data selecting unit selects data having the largest number of empty slots as the management target data from the threshold list. A data storage step of storing the management target data selected from the data in page units read from the flash memory in a dedicated area of a buffer memory including a general area and a dedicated area; A data recording step of recording the recording target data to be recorded in the flash memory into an area corresponding to an empty slot of a page composed of the management target data in a dedicated region of the buffer memory; A data removing step of removing from the dedicated area of the buffer memory if the number of empty slots of the page comprising the management target data is equal to or less than a first reference number; And And a flash memory accessing step of storing management target data removed from the dedicated area of the buffer memory in the flash memory. The method of claim 7, wherein And a management target data selection step of selecting data having the number of empty slots equal to or greater than a second reference number from among the page unit data read from the flash memory as the management target data. How to manage. The method according to claim 7 or 8, When the management target data is removed, the management target data replacement step of selecting data for which the number of empty slots is greater than or equal to a third reference number from among the page unit data stored in the general-purpose area as the management target data and moving it to the dedicated area. And a buffer management method interoperating with the flash memory. The method of claim 7, wherein A threshold list generation step of searching for data having a number of empty slots equal to or greater than a fourth reference number among data in page units read from the flash memory, and generating a threshold list that is a list of address information indicating the retrieved data; And And a selection step of selecting management target data for selecting the management target data from the threshold list. The method of claim 10, And a threshold list updating step of updating the threshold list when data in units of pages stored in the general-purpose area is changed or data in units of pages is removed from the general-purpose area. Buffer management method The method of claim 10, The managing data selection step is a buffer management method that is linked to the flash memory, characterized in that for selecting the data that the largest number of empty slots from the threshold list as the management target data. A computer-readable recording medium having recorded thereon a program for causing a computer to execute a buffer management method as recited in any one of claims 7, 8, 10, 11 or 12.

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