JPH0540692A - Duplicate area managing system - Google Patents

Abstract

PURPOSE:To remarkably reduce the overhead of duplication in an operating system. CONSTITUTION:A same physical address space 1 is allocated to plural virtual address space 2, 3. Write on the virtual address space 2, 3 are prohibited. When the exception of prohibited write on a virtual page 7 occurs, another physical page is acquired, and the content of a physical page 8 is duplicated on the page. A partial duplication instruction flag 10 instructs whether the duplication of whole content or partial duplication of the page should be performed. A partial duplication instruction table 14 describes a duplicate area 6 to be duplicated of the page.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copy area management system, and more particularly, it assigns the same physical address to a plurality of virtual addresses, disables writing to the virtual addresses, and when a write exception occurs. , A copy area management method of an operating system having a function of acquiring another physical page and copying a page including the virtual address to the acquired another physical page.

[0002]

2. Description of the Related Art In the conventional copy area management method, when a write exception occurs, another physical page is acquired and the page including the virtual address where the exception is generated is copied to the acquired another physical page. Was.

[0003]

The above-mentioned conventional copy area management method of the operating system is wasteful when the area to be copied is smaller than the page because all the pages are copied when an exception occurs. However, it has a drawback that the overhead becomes large.

[0004]

A copy area management system of the present invention has a function of allocating a physical address in a storage device to a virtual address recognized by a CPU in units of pages of a certain size, and writing permission to the virtual address. A memory management device having a function of setting the disapproval for each page and a function of generating an exception to the CPU when writing to the disapproval page is used, and a plurality of virtual addresses have the same physical address. Is assigned to the virtual address and writing to the virtual address is prohibited. When writing to the unauthorized page occurs and an exception occurs, another physical page is acquired, and the content of the physical page is acquired from another acquired physical page. In the operating system copy area management method that has the function of copying to a physical page,
Each page has a partial copy instruction flag for determining whether to copy the entire contents of the page or a partial copy, and
It is configured by having a partial copy instruction table which describes a copy area to be copied in a page.

[0005]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of a copy area management system of the present invention. 2 is a diagram showing an example of another physical page acquired when a write exception occurs in this embodiment.

As shown in FIG. 1, the physical page 8 in the physical address space 1 is allocated to the virtual page 7 in the virtual address space 2 and the virtual page 4 in the virtual address space 3. Further, there is a page table 9 containing information for allocating the physical address space 1 to the virtual address space 2, and there is a page table entry 13 containing information for one page. Then, in the page table entry 13, address translation information 12 for allocating the physical page 8 to the virtual page 7,
A write permission flag 11 and a partial copy instruction flag 10 are included. And, normally, the write permission flag 11 is not set. When the partial copy instruction flag 10 is set, the copy area instruction table 14 is referred to. The virtual page 7 is included in the partial copy instruction table 14.
There is a partial copy instruction table entry 15 that holds information corresponding to. Offset field 1 within page of copy area in partial copy instruction table entry 15
6 holds the value of the in-page offset address 5 of the copy area 6 to be originally copied. The size of the copy area 6 is held in the size field 17 of the copy area.

On the other hand, the copy area 18 is an area in the physical address space 1 allocated to the copy area 6. FIG. 2 shows a change in the situation when writing occurs at an address in the size field 17 of the copy area in the state of FIG. That is, when an exception occurs due to writing, the conventional operating system acquires another physical page 20, copies all the contents of the physical page 8 to another physical page 20, and changes the contents of the address translation information 12. By doing so, another physical page 20 is allocated to the virtual page 7.

However, in the copy area management system of the present invention,
When the exception occurs, the state of the partial copy instruction flag 10 is checked. When the partial copy instruction flag 10 is set, the contents of the page offset field 16 of the copy area and the size field 17 of the copy area are referred to, and the write operation is performed. When the existing address is included in the copy area 6, another physical page 20 is acquired, then only the copy area 18 is copied to the copy area 19, and another physical page 20 is allocated to the virtual page 7. This eliminates the need to unnecessarily copy the entire page.

[0010]

As described above, the copy area management system of the present invention can greatly reduce the copy overhead of the operating system by using the partial copy instruction flag and the partial copy instruction table. It has the effect.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a copy area management system of the present invention.

FIG. 2 is a diagram showing an example of another physical page acquired when a write exception occurs in this embodiment.

[Description of Codes] 1 physical address space 2,3 virtual address space 4,7 virtual page 5 page offset 6,18,19 copy area 8 physical page 9 page table 10 partial copy instruction flag 11 write enable flag 12 address translation information 13 page table entry 14 partial copy instruction table 15 partial copy instruction table entry 16 offset field within page of copy area 17 size field of copy area 20 another physical page

Claims (1)

[Claims] 1. A function of allocating a physical address in a storage device to a virtual address recognized by a CPU in units of pages of a certain size, a function of setting write permission and prohibition for a virtual address for each page, and a non-permission A memory management device having a function of generating an exception to the CPU when writing to a page is used, the same physical address is assigned to a plurality of virtual addresses, and writing to the virtual addresses is prohibited. Every other time, when a write occurs to the unauthorized page and an exception occurs, another physical page is acquired, and the copy area of the operating system having a function of copying the content of the physical page to the acquired another physical page In the management method, determine whether to copy all or part of the page contents for each page And a partial copy instruction table that describes a copy area to be copied in a page.