JPH022175B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a page table creation control method in a virtual memory system, and in particular, a method for reserving a virtual storage area for a page table when creating a space for a virtual storage area. This invention relates to a page table creation control method that allocates real pages in main memory when actually used.

(Prior Art) A data processing device uses a virtual memory method to expand memory space. In the virtual memory method, as shown in FIG. 3, the virtual space 1 is divided into segments SG0, SG1, etc. of a certain size. In SGN, each segment is a page of a certain size PG0,
The pages are divided into PG1...PGm, pages containing data to be actually used are stored in the main memory 2, and data processing is executed based on these pages.

Therefore, in order to obtain the storage address of where in the main memory 2 the data necessary for data processing is stored, a segment table SGT and a page table PGT are provided as shown in FIG. Enter the start address of the segment's page table PGT, and the storage address of each page of the segment is entered in the page table PGT. In this case, only one segment table SGT exists, but a page table PGT is created for each segment. Therefore, conventionally, when a page in a segment is transferred to the main memory 2, a page table PGT is created and a valid bit is written in that segment in the segment table. for example,
As shown in Figure 3, page PG in segment 3
3-x and page PG (N-
1) When -y is stored in main memory 2, page table PGT3 of segment 3 and page table PGT-(N-1) of segment N-1 are created in these empty parts, and the page address of each segment is is stored. Then, invalid bits were written on a page-by-page basis as data processing progressed.

In such cases, new segment 2
If data existing in page PG2-z in segment 2 is needed, it is first necessary to create page table PGT-2 for segment 2. At this time, there is no problem if there is a free space in which this page table PGT-2 can be created within the segment where the page table has already been created, but if such a free space does not exist, this page table PGT-2 It is necessary to create a page table for the segment of the virtual space area required to create the virtual space area. For example, this page table PGT-2 is allocated to segment n, and for this purpose it is also necessary to allocate an area for the page table of this segment n.

[Problem that the invention seeks to solve]

The problem to be solved by the present invention, as described above, is the recursion that when performing allocation processing of a virtual storage area on main memory, another allocation processing is required to create a necessary page table. , which complicates the processing. Furthermore, in order to obtain the address of a page table in a certain area, it is necessary to convert the address in the main memory of the page table in the segment table SGT to an address in virtual memory.

[Means for solving problems]

In order to solve the above problems, the page table creation control method of the present invention divides the virtual space into a plurality of segments, divides each segment into pages, and determines the location of the page table for each segment in main memory. In a virtual memory management method that includes a segment table that indicates the page portion of each segment and a page table that indicates the location of the page portion in each segment in main memory, a segment detection unit that detects that a segment has been switched and a page table that indicates the location of the page portion in each segment in the main memory. In addition to providing a page table creation control unit to create a page table, a page table area for each segment is reserved in advance in the virtual space, and when a segment changes, the page table area in the virtual space that has already been reserved is used as the main page table in the corresponding segment table. It is characterized by being configured so that areas on memory are associated with each other and addresses on the main memory are entered.

[Effect]

According to the present invention, all virtual space areas used as page tables for each segment are continuously reserved when creating a virtual storage area, so when a segment is allocated to main memory, the pages corresponding to the segment are If there is no table, the area in the virtual space has already been acquired through the continuous reservation described above, so not only can the reserved area be easily determined, but it can also be used as a page table by allocating a real page to the determined area. be able to. Therefore, it does not become a recursion as in the past.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a reserved area reserved for a page table.

First, the reserved area reserved for the page table, which is a characteristic feature of the present invention, will be explained with reference to FIG.

In the present invention, when creating a virtual storage area space, all virtual storage areas used as page tables for each segment are continuously reserved in advance. For example, if the size of the virtual storage space is XMB, and the size of one segment is 1MB, and the page table for this requires 1 byte (hardware and software used area together), the entire page table The reserve area requires (X*l) bytes. Therefore, when the reserved area of the page table is allocated to each segment in order, the result will be as shown in FIG.
Therefore, the low address P of the page table in the area of address n can be obtained as follows, where A is the low address of the reserved area: P=A+(n/1MB)*l (1).

The configuration of the present invention will be explained with reference to FIG.

In Figure 1, 10 is the CPU, 20 is the main memory,
30 is an external storage device.

The CPU 10 includes a segment switching detection unit 11 that detects segment switching due to execution of a job, a page table creation control unit 12 that performs various controls for creating a page table, and a page table creation control unit 12 that performs various controls for creating a page table in the main memory 20. Table area address holding unit 1 that holds the page table reserve position (A in FIG. 2) in the virtual storage area
3rd class is provided.

The main memory 20 stores a program area 21 in which programs necessary to execute a job are stored, a table area 22 in which segment tables and page tables are created, the position of the segment table, the size l of the page table, etc. A table 23 and the like are provided.

The external storage device 30 is provided with a reserved area for a page table shown in FIG. 2, in addition to various programs and data necessary to execute a job.

Next, the operation of the present invention will be explained.

CPU 10 executes jobs based on programs stored in main memory 20. When data in another segment becomes necessary due to execution of a job, the segment switching detection unit 11 detects this and controls page table creation to determine whether a page table for that segment exists in the main memory 20. section 12 detects.

If the page table for that segment exists on the main memory 20, the necessary data is read from the main memory 20 or the external storage device 30,
Continue data processing.

However, if the page table for that segment does not exist on the main memory 20, the page table creation control unit 12 calculates the above equation (1) based on the address n of the required data to locate the segment. The page table reservation destination is calculated according to the page table, a new page table for that segment is created on the main memory 20, and the start address of the new page table is written in the segment entry of the segment table. After allocating real pages to the reserved area and creating a page table in this way, the necessary data is read from the external storage device 30 and the job is continued based on this.

〔Effect of the invention〕

According to the present invention, the page table area for each segment is continuously reserved in advance in the virtual storage area in the order of the segments, so even when creating a new page table, that area is reserved in the virtual storage area. This allows the conventional recursion to be avoided. Furthermore, since the reserved positions exist consecutively in segment order, the address of the page table can be easily determined, and the number of steps can also be reduced.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 is an explanatory diagram of a reserved area reserved for a page table, Fig. 3 is an explanatory diagram of the relationship between virtual space and main memory, and Fig. 4 is an illustration of a segment table. FIG. 3 is a relationship explanatory diagram of page tables. In the figure, 10 is a CPU, 20 is a main memory, and 30 is an external storage device.

Claims (1)

[Claims] 1 The virtual space is divided into multiple segments, each segment is divided into pages, and a segment table indicating the location in main memory where the page table for each segment exists, and the page part within each segment exists in main memory. In a virtual memory management system that includes a page table that indicates the location of a segment, a segment detection unit that detects when a segment has been switched and a page table creation control unit that creates a page table are provided. Allocate a table area in advance, and when a segment changes, associate the area in main memory with the page table in the virtual space that has already been allocated in the corresponding segment table, and write the address in main memory. A page table creation control method characterized by being configured as follows.