JPS62197843A - File access system - Google Patents

Abstract

PURPOSE:To attain improvement of the memory availability as well as a high processing speed with a file access system by controlling the entire area of a file used in a system after projecting it into a logical space. CONSTITUTION:A program 1 requests a file I/O to a file I/O logic 2 and the logic 2 refers to a file area control table 3 based on the file name and the intra-file offset to obtain a logic address within the corresponding file I/O logic space 4. If no memory is allocated to the space 4 in a memory transfer mode, a memory access fault is produced and a demand paging logic 5 is started. Then a physical memory is allocated to the corresponding area in the space 4 and the table 3 is updated. Then a file I/O logic 6 works to read data out of a disk 8 to the space 4 or to allocate an idle block of the disk 8 to a file. Then the corresponding information is registered to a file area control table 7.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a file access method for accessing disk files in a data processing system.

<Conventional technology> In order to enable high-speed file access, some of the file data that is likely to be used in the future is stored in memory, thereby reducing the number of physical accesses to the disk. A cache buffer is used for this purpose. As a method for selecting data to be stored in this cache buffer, LRU (Least Receive
ntly Used ) logic is used. The cache buffer stores data in units of n fixed sectors as its address space.

In general data processing, it is possible to reduce the number of accesses to the disk by increasing the number of cache buffers, but if the number of cache buffers is increased unnecessarily, not only will the overhead of searching for data in the cache buffer become large, but also the number of accesses will be reduced. Memory usage efficiency was reduced when the amount of data was small.

<Object of the Invention> The present invention has been made in view of the above circumstances, and aims to provide a file access method that achieves improved memory usage efficiency and faster processing.

<Summary of the Invention> In the present invention, an empty logical space directly accessed by the CPU is allocated as a logical space for file I/O, and file data required for program processing is stored. This file I/O
File management is performed using the logical space management table. Further, when a fault occurs in accessing a file, virtual storage processing (demand paging) is performed between the disk and the logical space for file I/O.

In other words, memory (for execution) □ memory (file l/
Separate the transfer processing of O) from the transfer processing of memory (file I/O)□ disk files.

By doing so, the number of data searches when using a conventional cache buffer can be reduced, and high-speed processing can be achieved. Furthermore, memory can be used efficiently by managing virtual memory by combining the logical space for file I/O and the program storage space.

<Example> The file access method of this example consists of the following processing steps.

i) Provide a logical space for file I/O within a logical space to which memory can be allocated and accessed by system programs.

ii) The open file is file■/O
Allocate a logical space that is large enough to cover the entire area of the file.

iii) All program file I/O ii)
It is processed as a memory-to-memory transfer between the file I/O logical space allocated in and the program.

iv) Ilo to the file area in the disk is iii
) is executed by the virtual memory management logic activated by an access fault that occurs during the process.

File I/O consists of a) opening a file;

This is performed in the sequence of b) Ilo of file data, and c) closing of the file. The details of this sequence will be explained below based on the drawings.

a) The file open program 1 notifies the file I/O logic 2 of the file name to be input/output from now on.

The file I/O logic 2 secures a continuous area large enough to cover the entire area of the specified file, and registers the file name and the start logical address of this continuous area in the file area management table 3 (of course, the continuous area (Although it does not have to be a continuous area here for simplicity, it is assumed to be a continuous area). At this time, for files that already have data on the disk, area information of the disk in use is registered in the file area management table 7.

b) File Ilo Program 1 includes the file name and offset within the file,
Buffer address in program, ■/O size, ■/O
A file I/O request is made to the file I/O logic 2 using the type of file as a parameter. The file I/O logic 2 refers to the file area management table 3 based on the file name and intra-file offset to find the corresponding logical address in the logical space 4 for file I/O. Memory transfer for the I/O size is performed between the program buffer and the determined file I/O logical space area. The direction of memory transfer is determined by the type of Ilo. If memory is not allocated to the file I/O logical space 4 during this memory transfer, a memory access fault occurs, the demand paging logic 5 is activated, and the corresponding area in the file I/O logical space 4 is allocated. Allocate physical memory and update the file area management table 3. Next, the file I/O logic 6 operates to transfer data from the disk 8 to the file! /O logical space 4 (when file data is already registered on disk 8), or allocate an empty block on disk 8 to the file and register the information in file area management table 7 (when expanding the file) . After this, the process returns to the memory transfer operation described above.

C) The file close program 1 notifies the file I/O logic 2 of the name of the file to be closed. File ■/O logic 2 instructs file I/O logic 6 to close the file. File! The /O logic 6 writes the memory data remaining in the file I/O logical space 4 to the disk 8 using the information in the file area management table 7.

The physical memory allocated for this file in the file I/O logical space 4 is released, and the file area management table 3. All information for this file is deleted from the file I/O logical space 4 and the file area management table 7.

<Effects of the Invention> As explained above, in the present invention, the entire area of files used within the system is mapped and managed in the logical space of the system, and the cache buffer management logic is integrated into the virtual memory of the program section. Since it is shared with the management logic, it is possible to improve memory usage efficiency and speed up processing.

[Brief explanation of drawings]

The drawing is a block diagram showing the functional configuration of an embodiment of the present invention. 1.-Program 2.6--File I/O logic 3.7.--File area management table 4-File I
/O logical space 5 - Demand paging logic 8 --- Disk

Claims (1)

[Claims] Allocate an empty logical space in memory as a logical space for file I/O, store file data necessary for program processing in this logical space for file I/O, and use the management table of this logical space for file I/O to A file access method characterized by performing file management and virtual memory management between a file I/O logical space and a disk file.