JP2008140236A - Memory management system, information processor and memory management method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a memory management system reducing an amount of saved data, suitable for a computer system rewriting read-only data on a main storage device for operation. <P>SOLUTION: This memory management system has a difference extraction/restoration processing part 4 as a data save means and a data restoration means. When a swap-out request occurs, the difference extraction/restoration processing part 4 extracts difference data 32 between partial data 12 to be saved determined by prescribed page replacement algorithm and the read-only data corresponding to the partial data 12, and writes them to a swap device 3 together with the read-only data and an identifier 31 showing a location of the difference. When a swap-in requirement occurs, the difference extraction/restoration processing part 4 restores the partial data 12 from the difference data 32 written to the swap device 3 and the read-only data specified by the identifier 31. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a memory management system, an information processing apparatus, and a memory management method, and in particular, a memory management system suitably applied to an embedded computer system such as a mobile phone, a car navigation system, and various information home appliances, and information provided therewith The present invention relates to a processing device and a memory management method.

  Patent Document 1 discloses a virtual memory system that selects and executes swap-out in units of pages or swap-out in units of tasks based on a memory area securing request from a task.

  Also, for example, in Patent Document 2, a multi-bit vector in which the access history of each page is recorded is evaluated instead of the LRU (Least Recently Used) method based on the access / non-access display bit flag of each page. A technique for reducing a swap fault by swapping out a page with a small number of times is disclosed.

JP 2001-216185 A JP-A-6-89222

  In an embedded computer system such as a mobile phone, a car navigation system, and various information home appliances, it is normal to operate read-only software written in a ROM or flash memory in advance on a main storage device as necessary. . When any change is made to the data section in the above operation process, the data related to the change is handled as private data, and at the time of swap-out, the contents of the page including the data are written to the swap device.

  Embedded computer systems such as mobile phones, car navigation systems, and various information home appliances generally have a limited amount of storage used as the swap device as well as the main storage device, reducing the amount of data at the time of swap-out. It is requested to do.

  However, the amount of data at the time of swap-out is equal to the swap target range when writing without compression, and compression is performed by referring only to the data in the page even when a compressed recording method is adopted. For this reason, the compression rate has a certain limit.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the amount of data at the time of the swap-out and to manage the memory suitably applicable to the embedded computer system. A system and a memory management method are provided.

  According to a first aspect of the present invention, there is provided a memory management system for a computer that operates by reading read-only data and rewriting on a main storage device, and data to be saved determined by a predetermined page replacement algorithm; Extracting difference data from the read-only data corresponding to the data, and writing the data to a predetermined save area, the difference data written to the save area, and the read-only data corresponding to the difference data, There is provided a memory management system characterized by comprising data restoration means for restoring data to be restored to a main storage device, and an information processing apparatus equipped with the memory management system.

  According to a second aspect of the present invention, there is provided a memory management method in a computer that operates by reading read-only data and rewriting on a main storage device, wherein the computer saves data determined by a predetermined page replacement algorithm. And the step of extracting the difference data between the data and the read-only data corresponding to the data and writing the difference data to the predetermined save area, the difference data written to the predetermined save area by the computer system, and the difference data And restoring the data to be restored to the main memory from the corresponding read-only data.

  According to the present invention, the amount of data at the time of swap-out can be reduced, and the swap area can be used efficiently. The reason is that only the difference between the swap target data and the read-only data is set as the save target when swapping out.

  Next, the best mode for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a memory management system according to the first embodiment of the present invention. Referring to FIG. 1, a main storage device 1, a read-only file system (hereinafter referred to as “FS”) 2, a swap device 3 composed of storage devices and the like, and a difference that functions as a data saving unit and a data restoring unit. An extraction / restoration processing unit 4 is shown.

  When the file 20 on the FS 2 is read to the main storage device 1, it is managed by the partial data 12 divided into pages and the identifier 11 assigned to each partial data 12. The identifier 11 is information indicating the original file (the file 20 on the FS 2) and the in-file offset, and is used when obtaining a difference between the file 20 on the FS 2 and the partial data 12. The partial data 12 represents data of one page of an arbitrary size read into the main storage device 1.

  The swap device 3 is a device that records the swap data 30. The swap data 30 includes an identifier 31 indicating information indicating the original file (file 20 on the FS2), an offset in the file (difference occurrence position), and FS2. And the difference data 32 of the partial data 12 on the main storage device 1.

  Next, referring to FIG. 1, regarding the operation of the present embodiment, the file 20 is read from the FS 2, the data is changed on the main storage device 1, and then written to the swap device 3 (swap out), followed by the swap device. A series of operations from reading 3 to reading (swap-in) will be described.

  First, the file 20 of the FS 2 is read into the main storage device 1. Immediately after the file 20 is read into the main storage device 1, each partial data 12 has exactly the same contents as the corresponding part of the file 20.

  Thereafter, when the content of the partial data 12 is changed by the operation of the program or the like, the partial data 12 is handled as private data.

  Thereafter, when it becomes necessary to write the partial data 12 to the swap device 3 due to memory shortage or the like, the partial data 12 is transferred to the difference extraction / restoration processing unit 4 together with the identifier 11. The difference extraction / restoration processing unit 4 reads the corresponding portion of the file 20 specified from the identifier 11, compares it with the partial data 12, and extracts the difference data 32.

  The difference extraction / restoration processing unit 4 writes the swap data 30 with the identifier 31 added to the extracted difference data 32 to the swap device 3.

  Thereafter, when it becomes necessary to read the swap data 30 written to the swap device 3, the difference extraction / restoration processing unit 4 specifies the corresponding part in the original file 20 from the identifier 31 in the swap data 30. Then, the partial data 12 is restored by applying the difference data 32 to the corresponding part in the file 20.

  As described above, according to the present invention, the capacity required for the swap device 3 can be reduced. The reason is that the amount of data to be written to the swap device can be reduced by taking the difference from the data (file 20) that is the source of the private data when writing to the swap device 3 and reducing the redundancy of the data to be saved. Because.

  Theoretically, when all parts of all the partial data 12 are changed, the difference data 32 has the same data amount as the partial data 12, but this is the worst case. In general, since there is little change in all parts, a significant reduction in data amount can be expected.

  Of course, from the viewpoint of further reducing the data amount of the difference data, after extracting the difference data, the compression / difference data may be created and written to the swap device 3 using an arbitrary compression method. In this case, when the swap data 30 needs to be read out, the differential extraction / restoration processing unit 4 performs the decompression (decompression) operation using the compression method, and then the corresponding part specified by the identifier 31. Will be applied.

  Next, the second embodiment of the present invention in which the data saving destination of the first embodiment of the present invention is changed will be described. FIG. 2 is a diagram showing a schematic configuration of a memory management system according to the second embodiment of the present invention. Referring to FIG. 2, the basic configuration of this embodiment is the same as that of the first embodiment (see FIG. 1), but the swap area 13 corresponding to the swap device 3 of FIG. Is provided.

  According to the present embodiment, the swap data 130 is not written to the external swap device 3 but is stored in the swap area 13 in the main storage device 1.

  According to the present embodiment, not only the swap device 3 is unnecessary, but also the size of the difference data 132 in the swap data 130 can be made smaller than that of the partial data 12, so that the main memory is compared with a configuration that does not take a difference. The amount of use of the device 1 can be further reduced.

  As described above, each embodiment of the present invention has been described, but the technical scope of the present invention is not limited to the description of each embodiment described above, and according to the specifications of the information processing apparatus to be applied, etc. Various modifications can be made.

1 is a diagram illustrating a schematic configuration of a memory management system according to a first embodiment of the present invention. It is a figure showing schematic structure of the memory management system which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

1 Main storage device 2 Read-only file system 3 Swap device
4 Difference extraction / restoration processing unit 11, 31, 131 Identifier 12 Partial data 13 Swap area 20 File 30, 130 Swap data 32, 132 Difference data

Claims (8)

A memory management system for a computer that reads read-only data and rewrites and operates on a main storage device.
Data saving means for extracting difference data between data to be saved determined by a predetermined replacement algorithm and read-only data corresponding to the data, and writing the data in a predetermined saving area;
Data restoration means for restoring data to be restored to a main storage device from the difference data written to the save area and the read-only data corresponding to the difference data;
A memory management system. The data saving unit writes together with the difference data, identifier information indicating a portion to which the difference data should be applied in the read-only data,
The data restoring means restores data to be restored to the main storage device by applying differential data based on the identifier information;
The memory management system according to claim 1. The data saving unit writes the difference data in the predetermined save area after compressing the difference data by a predetermined compression method,
The data restoring means is configured to restore data to be restored to the main storage device from the difference data restored from the compressed difference data written to the predetermined save area and the read-only data corresponding to the difference data. Restoring,
The memory management system according to claim 1, wherein: The main storage device is provided with a save-only area used as the predetermined save area,
The memory management system according to any one of claims 1 to 3.   An information processing apparatus equipped with the memory management system according to claim 1. A memory management method in a computer that reads read-only data and operates by rewriting on a main storage device,
The computer extracts difference data between data to be saved determined by a predetermined replacement algorithm and read-only data corresponding to the data, and writes it to a predetermined save area;
Restoring the data to be restored to the main storage device from the difference data written in the predetermined save area by the computer and the read-only data corresponding to the difference data;
A memory management method characterized by the above. The computer writes, together with the difference data, identifier information indicating a portion to which the difference data is to be applied in the read-only data, and applies the difference data based on the identifier information to restore to the main storage device Restoring the data to be
The memory management method according to claim 6. The computer compresses the difference data by a predetermined compression method, writes the difference data to the predetermined save area, restores the difference data restored from the compressed difference data written to the predetermined save area, and the difference data Restoring the data to be restored to the main storage device from the read-only data corresponding to
The memory management method according to claim 6 or 7, wherein:

Images