JP2007334687A - Information processor and file access method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent meta-data, a setting file or the like likely to be reused from being expelled from a cache buffer, and to provide the efficient file access without changing any application. <P>SOLUTION: An information processor for handling the file stored in a secondary storage unit has a determination means for determining whether or not the file to be accessed is likely to be reused. If the determination means determines that the file to be accessed is not likely to be reused, the file is accessed without using any cache buffer. If the determination means determines that the file to be accessed is likely to be reused, an access means is further provided for making access to the file by using the cache buffer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an information processing apparatus and a file access method.

  A file system normally uses a storage area called a cache buffer. When there is a file read request from an application, the file system transfers the data of the corresponding file from a secondary storage device such as a hard disk or a memory card to the cache buffer in units of sectors. Next, the file system transfers only the requested data from the cache buffer to the memory area designated by the application.

  The contents of the cache buffer are retained as much as possible, and when the application requests to read the same data again, the file system skips the transfer from the secondary storage device and stores the cache buffer data in the memory area specified by the application. Forward. As a result, access to the secondary storage device that operates slowly can be reduced, which is effective in improving the speed.

  When there is a write request to the file from the application, the file system transfers the data designated by the application to the cache buffer, and then transfers it to the secondary storage device. The file system can delay the actual data transfer from the cache buffer to the secondary storage. Therefore, when there is an overwrite request for the same data from the application before transferring to the secondary storage device, the file system changes only the data in the cache buffer and transfers only the last change result to the secondary storage device. This can reduce access to the secondary storage device.

  Further, the file system has metadata such as directory entry, FAT, and inode necessary for accessing the file. When the file system reads or writes metadata, the file system once transfers the metadata to the cache buffer and accesses the metadata on the cache buffer.

  In this way, the file system retains the data once transferred to the cache buffer as much as possible, and discards the old data for the first time when the cache buffer is completely used up. Use for Thus, the file system efficiently realizes file access.

JP-A-2003-122606

  In recent years, an increasing number of devices handle large-capacity multimedia data such as images, audio, and video. With the exception of some devices that can edit data, these devices continuously access from the beginning to the end of a large-capacity file when handling multimedia data. Alternatively, these devices often repeat access to different files one after another. In other words, it is extremely rare to read or rewrite specific data in a file many times. Also, even a device that handles a large amount of data has a small storage area that can be used as a cache buffer, and many of the data of one file cannot fit into the cache buffer in many cases.

  However, these devices read and write such a large amount of data via the cache buffer. Therefore, when accessing large-capacity multimedia data, there is a problem that a limited cache buffer is exclusively used for the large-capacity multimedia data, and the contents of metadata and setting files are evicted.

  The present invention has been made in view of such problems, and prevents metadata and configuration files that are highly likely to be reused from being flushed out of the cache buffer, thereby enabling efficient file access without application changes. The purpose is to provide.

  Therefore, the present invention is an information processing apparatus that handles a file stored in a secondary storage device, and includes a determination unit that determines whether or not the accessed file is a file that is unlikely to be reused. When the determination unit determines that the file to be accessed is a file that is unlikely to be reused, the file is accessed without using a cache buffer, and the file to be accessed is determined by the determination unit. When the file is determined to be a file that is highly likely to be reused, it further includes an access means for accessing the file using the cache buffer.

  By adopting such a configuration, for example, when accessing data that is unlikely to be reused, the data can be accessed without going through the cache buffer. Therefore, it is possible to prevent metadata and setting files that are likely to be reused from being evicted from the cache buffer, and to provide efficient file access without application changes.

  The present invention may be a file access method.

  According to the present invention, it is possible to prevent metadata and setting files that are highly likely to be reused from being flushed out of the cache buffer, and to provide efficient file access without application changes.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a system configuration diagram of an example of a system capable of reading and writing data from and to a secondary storage device in the present embodiment. In FIG. 1, a processor 1 controls the entire system including a main storage device 2, an extension list 5, and a secondary storage device 6.

  The main storage device 2 includes a user area 3, a cache buffer 4, and an FD table 7. The user area 3 is an area designated by the application, and is an area containing data to be transferred to the secondary storage device 6 or an area containing data to be transferred from the secondary storage device 6. The processor 1 usually accesses the secondary storage device 6 through the cache buffer 4.

  As shown in FIG. 2, the FD table 7 has an area for storing a flag called NB for each file descriptor. FIG. 2 is a diagram illustrating an example of the FD table. The extension list 5 records file extensions that are unlikely to be reused as shown in FIG. FIG. 3 is a diagram illustrating an example of the extension list.

  The operation of the system of this embodiment will be described with reference to the flowchart of FIG. FIG. 4A is a flowchart (part 1) illustrating an example of the operation of the system according to the present embodiment. FIG. 4B is a flowchart (part 2) illustrating an example of the operation of the system according to the present embodiment. The flowchart in FIG. 4A describes only the characteristic part of the present embodiment regarding the open () that is called before the application handles the file among the programs running on the system of the present embodiment. The flowchart of FIG. 4-2 shows only the characteristic part of the present embodiment regarding read () / write () when the application reads and writes file data among the programs running on the system of the present embodiment. It is described.

  When the application calls open (), the open process of S1 is performed. The process of S1 shows the process of open () performed in a general system. The open () prepares and is necessary for accessing the file corresponding to the file name specified by the argument. Create a file if it exists. Open () assigns an ID called a file descriptor for accessing the file.

  If an error occurs because the specified file does not exist, cannot be created, or there is no access right, open () terminates the process.

  When the open process is successful, the process proceeds to S2. In S <b> 2, open () checks whether the extension of the given file name exists in the extension list 5. If present, in S3, open () sets the NB flag corresponding to the file descriptor given in the FD table to 1, and ends the process. If the given extension does not exist in the extension list 5, open () sets the corresponding NB flag to 0 in S4 and ends the process.

  Next, the operation of the system when an application calls read () / write () to access file data will be described with reference to the flowchart of FIG. First, read () / write () checks the NB flag corresponding to the file descriptor given as an argument in S11. If it is 1, the process proceeds to S12, and if it is 0, the process proceeds to S13.

  In S <b> 12, read () / write () performs read / write processing without using the cache buffer 4. Here, read () / write () transfers data directly between the secondary storage device 6 and the user area 3 if possible. However, when direct data transfer is not possible, read () / write () selects only one area for one sector from the cache buffer 4 and performs data transfer only through this cache buffer area. As a result, data already stored in the cache buffer is not expelled, or even if only one sector of data is expelled.

  As a case where direct data transfer is not possible, for example, the data length that can be handled by the secondary storage device 6 may be different from the data length specified by read () / write (). As a case where direct data transfer is not possible, for example, there is a case where the offset from the head of the data requested by the application is not a multiple of the sector which is the minimum unit of data that can be handled by the secondary storage device 6.

  In S <b> 13, read () / write () performs normal access using the cache buffer 4. When the process of S12 or S13 ends, read () / write () ends the process.

(Second Embodiment)
Next, an embodiment for determining whether a file has a file type DB instead of an extension list and is less likely to be reused will be described. Standard file formats such as JPEG, MPEG, and MP3 include characteristic data patterns in the first few bytes.

  For example, in the case of standard JPEG as an image file format, the first two bytes are 0xff and 0xd8. In the case of standard MPEG as a moving image file format, the first 4 bytes are 0x00, 0x00, 0x01, 0xb3. Therefore, by examining this, even if the extension of the file name is not reliable, the type of the data can be determined.

  FIG. 5 is a system configuration diagram of an example of a system capable of reading and writing data from and to the secondary storage device in the present embodiment. In FIG. 5, the processor 11 controls the entire system including the main storage device 12, the file type DB 15, and the secondary storage device 12.

  The main storage device 12 includes a user area 13, a cache buffer 14, and an FD table 17. The user area 13 is an area designated by the application, is an area that contains data to be transferred to the secondary storage device 16, or is an area where data is to be transferred from the secondary storage device 16. The processor 11 normally accesses the secondary storage device 16 through the cache buffer 14.

  The FD table 17 has an area for storing a flag called NB for each file descriptor. In the file type DB 15, a byte string that appears at the beginning of a file format that is unlikely to be reused as shown in FIG. 6 is recorded. FIG. 6 is a diagram illustrating an example of the file type DB.

  The operation of the system of this embodiment will be described using the flowcharts of FIGS. FIG. 7 is a flowchart (part 1) illustrating an example of the operation of the system according to the present embodiment. FIG. 8 is a flowchart (part 2) illustrating an example of the operation of the system of the present embodiment.

  Note that the flowchart of FIG. 7 describes only the characteristic part of this embodiment with respect to open () that is called before the application handles the file among the programs that run in the system of this embodiment. Further, the flowchart of FIG. 8 describes only the characteristic part of the present embodiment regarding read () / write () when reading / writing file data among the programs running on the system of the present embodiment. .

  When the application calls open (), the open process of S21 is performed. The process of S21 shows the process of open () performed in a general system. The open () prepares and is necessary for accessing the file corresponding to the file name specified by the argument. Create a file if it exists. Open () assigns an ID called a file descriptor for accessing the file.

  If an error occurs because the specified file does not exist, cannot be created, or there is no access right, open () terminates the process.

  If the open process is successful, the process proceeds to S22. In S22, open () checks whether or not the file given by the argument is a new file. If it is a new file, the process proceeds to S24, and if it is an existing file, the process proceeds to S23.

  In S24, open () sets the NB flag corresponding to the given file descriptor in the FD table to 2, and then ends the process.

  In S23, open () reads the top data of the file. The data length to be read is the longest number of bytes in the byte sequence registered in the file type DB 15. Thereafter, the process proceeds to S25, in which open () checks the byte string registered in the file type DB, and checks whether there is a match with the head data of the read file.

  If there is a matching byte string, open () proceeds to S26. If there is no matching byte string, open () proceeds to S27. In S26, open () sets the corresponding NB flag to 1 and ends the process. In S27, open () sets the corresponding NB flag to 0 and ends the process.

  Next, the operation when the application calls read () / write () to access file data will be described with reference to the flowchart of FIG. First, read () / write () checks the NB flag corresponding to the file descriptor given as an argument in S31. If it is 0, it goes to S35, if it is 1, it goes to S36. Proceed to S32.

  When the process proceeds to S32, it is a write () call for a new file, and a data string to be written is given as an argument. Here, write () checks the byte string registered in the file type DB, and checks whether there is a match with the head of the data string to be written.

  If there is a matching byte sequence, read () / write () proceeds to S34, and if there is no matching byte sequence, read () / write () proceeds to S33. In S33, read () / write () sets the corresponding NB flag to 0 and proceeds to S35. In S34, read () / write () sets the corresponding NB flag to 1, and proceeds to S36.

  In S35, read () / write () performs normal access using the cache buffer. In S36, read () / write () performs read / write processing without using a cache buffer. Here, read () / write () transfers data directly between the secondary storage device 16 and the user area 13 if possible. However, if direct data transfer is not possible, read () / write () selects only one area for one sector from the cache buffer 14 and performs data transfer only through this cache buffer area. As a result, data already stored in the cache buffer is not expelled, or even if only one sector of data is expelled.

  As a case where data cannot be directly transferred, for example, the data length that can be handled by the secondary storage device 16 is different from the data length specified by read () / write (). As a case where direct data transfer is not possible, for example, there is a case where the offset from the head of the data requested by the application is not a multiple of the sector which is the minimum unit of data that can be handled by the secondary storage device 16.

  When the process of S35 or S36 is finished, read () / write () finishes the end.

  As described above, according to each embodiment as described above, it is possible to prevent metadata and setting files that are highly likely to be reused from being evicted from the cache buffer, and to provide efficient file access without application changes. be able to.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to such specific embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims.・ Change is possible.

It is a system configuration figure of an example of a system which can read and write data to a secondary storage unit in this embodiment. It is a figure which shows an example of FD table. It is a figure which shows an example of an extension list | wrist. It is a flowchart (the 1) which shows an example of operation | movement of the system of this embodiment. It is a flowchart (the 2) which shows an example of operation | movement of the system of this embodiment. It is a system configuration figure of an example of a system which can read and write data to a secondary storage unit in this embodiment. It is a figure which shows an example of file type DB. It is a flowchart (the 1) which shows an example of operation | movement of the system of this embodiment. It is a flowchart (the 2) which shows an example of operation | movement of the system of this embodiment.

Explanation of symbols

1 processor 2 main storage device 3 user area 4 cache buffer 5 extension list 6 secondary storage device 7 FD table

Claims (6)

An information processing apparatus that handles files stored in a secondary storage device,
Determining means for determining whether or not the file to be accessed is a file that is unlikely to be reused;
If it is determined by the determination means that the file to be accessed is a file that is unlikely to be reused, the file is accessed without using a cache buffer, and the file to be accessed is determined by the determination means. An information processing apparatus, further comprising an access unit that accesses the file using the cache buffer when it is determined that the file has a high possibility of being reused. An information processing apparatus that handles files stored in a secondary storage device,
Determining means for determining whether or not the file to be accessed is a file that is unlikely to be reused;
If the determining means determines that the file to be accessed is a file that is unlikely to be reused, the file is accessed using a part of a cache buffer, and the determining means accesses the file. An information processing apparatus, further comprising: an access unit configured to access the file using a large part of the cache buffer when it is determined that the file is highly likely to be reused.   The determination means accesses the file stored in the secondary storage device using the extension information including the extension of the file format that is unlikely to be reused. The information processing apparatus according to claim 1, wherein it is determined whether the file is a low file.   The determination means uses the first byte string information including the first byte string of the file format that is unlikely to be reused, and the file stored in the secondary storage device that is accessed is reused. The information processing apparatus according to claim 1, wherein the information processing apparatus determines whether the file has a low possibility. A file access method in an information processing apparatus that handles a file stored in a secondary storage device,
Determining whether the file to be accessed is a file that is unlikely to be reused;
If it is determined in the determining step that the file to be accessed is a file that is unlikely to be reused, the file is accessed without using a cache buffer. In the determining step, the file to be accessed The file access method further comprising an access step of accessing the file using the cache buffer when it is determined that the file has a high possibility of being reused. A file access method in an information processing apparatus that handles a file stored in a secondary storage device,
Determining whether the file to be accessed is a file that is unlikely to be reused;
If it is determined in the determining step that the file to be accessed is a file that is unlikely to be reused, the file is accessed using a part of a cache buffer, and the file is accessed in the determining step. The file access method, further comprising: an access step of accessing the file using a large part of the cache buffer when it is determined that the file is highly likely to be reused.

Images