JPS61128348A - Address conversion system - Google Patents

Abstract

PURPOSE:To improve the using efficiency of a physical space by arranging one page table over uncontinuous plural pages on the physical space and arranging each entry on the way of each physical page. CONSTITUTION:A page table directory 2 is indexed by a virtual space No. (a) of a logical address A, a word 3 corresponding to the No. (a) is set up and a type bit 8 is formed in the word 3. A table 6 corresponding to a virtual page No. (b) is set up so that a pointer 4' specifies the starting physical address B in a page table 5' when the bit 8 is in the OFF status. On the contrary, the pointer 4' specifies the starting physical address of a page table 9 when the bit 8 is in the ON status. The table 9 is indexed to obtain a word 10. Then, the page table 5' of which starting physical address is specified by a pointer 11' is indexed to obtain a word 6. Then, an offset No. (c) is made apply to the physical space by a pointer 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an address conversion method used when converting a logical address into a physical address in a page address type data processing device.

[Technical Background of the Invention and Problems Therewith] Generally, in a data processing device using a page addressing method, a logical address including a virtual space number, a virtual page number, and an offset number within a page is used as a logical address including a physical page number and an offset number within a page. When converting into a physical address, a method as shown in FIG. 2 is adopted.

That is, a page table directory 2 whose starting physical address is specified by the pace register 1 is set in a memory having a predetermined physical space, and this page table directory 2 is indexed by the virtual space number a of the logical address A. A page table directory word 3 corresponding to each virtual space number is set.

Next, the page table 5 whose start physical address is specified by the page table pointer 4 provided in the page table directory word 3 is indexed by the virtual page number in the logical address A, and a page table corresponding to each virtual page number is created. Set word 6.

Furthermore, by applying the in-page offset number C of the logical address A to the physical page whose start physical address is specified by the page pointer 7 provided in the page table word 6, the logical address A is converted to the physical address B. be.

However, according to this method, since the page tables 5 must be continuous in the physical space, one page table occupies a considerably large physical space, resulting in inconveniences such as long access times. Ta.

Under these circumstances, an address translation method has been proposed in which the page table 5 can be divided and arranged into a plurality of pages in physical space.

This method will be explained based on FIG. Note that parts common to those in FIG. 2 are given the same reference numerals.

First, the page table directory 2 whose starting physical address is specified by the pace register 1 is indexed by the virtual space number a, and the page table directory word 3 corresponding to each virtual space number is set.

Here, a type bit 8 and a page table/page table table pointer 4' are provided in the page table directory word 3, and when the type bit 8 is in the OFF state, the page table/page table table pointer 4' is set to the starting physical address of the page table 5. be specified.

and page table 5 in which the starting physical address is specified.
is indexed by the page table index b2 which is a part of the virtual page number b' in the logical address A, and a page table word 6 corresponding to each page table index is set, and further provided in the page table word 6. The intra-page offset number C of the logical address A is applied to the physical page whose start physical address is specified by the page pointer 7.

On the other hand, when the type bit 8 is in the ON state, the page table/page table table pointer 4' specifies the starting physical address of the page table table 9, which is the table from which the page table is searched.

The page table table 9 designated by this is indexed by the page table table index b1 which is a part of the virtual page number b', and the page table table word 10 corresponding to each page table table index b1 is obtained.

Next, the page table 5 whose start physical address is designated by the page table pointer 11 set in the page table table word 10 is indexed by the page table index b2, and the page table word 6 corresponding to each page table index b2 is indexed. Set.

Furthermore, the intra-page offset number C of the logical address A is applied to the physical page whose starting physical address is specified by the page pointer 7 set in the page table word 6.

According to this method, one page table'.5 can be divided and arranged into multiple discontinuous pages in the physical space, but this time, each entry obtained by dividing the page table 5 can be Since each physical page must be written from the beginning, a problem arises in that the efficiency of physical space usage decreases.

[Object of the Invention] The present invention has been made in view of the circumstances described above. When converting a logical address into a physical address in a data processing device using a page address method, one page table is converted to a discontinuous one in physical space. To provide an address translation method that is highly efficient in the use of physical space and can be placed across multiple pages, and each entry obtained by dividing a page table can be placed in the middle of each physical page. It is an object.

[Summary of the Invention] That is, the present invention provides the following steps when converting a logical address including a virtual space number, a virtual page number, and an intra-page offset number into a physical address including a physical page number and an intra-page offset number in a physical space. a word having a field indicating an intra-page offset number of a first entry on a first page of a page table arranged across a plurality of page areas in the physical space; and a word in the virtual space in the logical address. A page table directory indexed by number,
an addition means for adding an intra-page offset number in the word and a virtual page number in the logical address; and a word for giving the position of each entry of a page table arranged in a plurality of page areas in the physical space. a page table indexed by the upper several bits of the addition result by the addition means; and a page table whose word having a field indicating the address of the page area is indexed by the lower several bits of the addition result by the addition means. This is an address conversion method characterized by providing the following.

[Embodiments of the invention] DESCRIPTION OF THE PREFERRED EMBODIMENTS Details of embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention, and parts common to FIGS. 2 and 3 are given the same reference numerals.

In the figure, A is a logical address to be converted to a physical address B, virtual space number a1 virtual page number b
It consists of an offset number C within one page.

Then, 1 is a pace register, 2 is a page table directory whose entry is a page table directory word 3 consisting of a page table/page table table pointer 4, a type bit 8, an intra-page offset number 12, and other fields, which will be described later. It shows. Note that the page table/page table pointer 4 is a pointer that specifies the start physical address of the page 5' of the page table 9 or the page table described later.

In addition, type bit 8 indicates whether the page table spans multiple pages that are discontinuous in physical space, and intra-page offset number 12 indicates the offset number of the first entry on the first page of the page table that spans multiple pages. It shows.

Page 5' of the page table is the y-th page of the page table whose entry is page table word 6 when the value of page table table index d2 (described later) is y.
It is the second page and 1. The page table word 6 is a page pointer 7 that specifies the starting physical address of the physical page.
and other fields.

The page table table 9 has a page table table word 10 as an entry, and the page table table word 10 consists of a page table pointer 11' and other fields. Note that the page table pointer 11' points to the y-th page 5' of the page table.
This is a pointer indicating the starting physical address of .

Reference numeral 13 denotes an addition means for adding the virtual page number and intra-page offset number 12, and 14 is a register for storing the addition result (hereinafter referred to as a calculated value) d by the addition means 13. This calculated value d is divided into a page table index d1 and a page table index d2. That is, the lower bits of the enhan value d are set as the page table index d1, and the bits obtained by removing the lower bits from the calculated value d are set as the page table index d2.

Note that K indicating the bit width is a positive integer such that M-2KN holds when the size of one page of the page table is M bits and the size of page table word 6 is N bits.

The address translation method of this embodiment configured in this way is as follows:
First, the page table directory 2 whose starting physical address is specified by the pace register 1 is indexed by the virtual space number a, and the page table directory word 3 corresponding to each virtual space number a is set. type bit 8
will be established.

When this type bit 8 is OFF, the page table/page table table pointer 4' specifies the starting physical address of the page table 5', and the page table 5' is set to the virtual page number of the logical address A. A page table word 6 is set corresponding to each virtual page number by indexing, and the intra-page offset number C of the logical address A is adapted to the physical space whose starting physical address is specified by the page pointer 7.

On the other hand, when type bit 8 is ON,
Page table/page table table pointer 4'
specifies the starting physical address of the page table 9.

Then, the means 1 adds the virtual page number in the logical address A and the intra-page offset number 12 in the page table directory word 3 of the page table directory 2.
3, and the calculated value d is stored in the register 14.

Next, a starting physical address is specified by the page table/page table tape and register pointer 4'.

The page table table 9 is indexed by the page table table index d2 to obtain the page table table word 10 corresponding to each page table table index d2.

The page table 5' whose starting physical address is specified by the page table pointer 11' is roughly indexed by the page table index d+ to obtain the page table word 6 corresponding to the page table index d1, and then by the page pointer 7. The in-page offset number C of the logical address A is applied to the physical space designated by the starting physical address. This process converts logical address A into physical address B.

[Effects of the Invention] As explained above, the address conversion method of the present invention converts a logical address including a virtual space number, a virtual page number, and an intra-page offset number into a physical page number and an intra-page offset number in a physical space. When converting into a physical address containing a word, a word having a field indicating the intra-page offset number of the first entry of the first page of the page table arranged across multiple page areas in the physical space, and a page table directory indexed by the virtual space number in the logical address; an addition means for adding an intra-page offset number in the word to a virtual page number in the logical address; and a plurality of page table directories in the physical space. A page table table in which the word to be given is indexed by the upper few bits of the addition result by the addition means, and the word having a field indicating the address of the page area is the lower number of the addition result by the addition means. By providing a page table that is indexed by bits, it is possible to arrange one page table across multiple discontinuous pages in physical space, and each page table obtained by dividing the page table Entries can be placed in the middle of each physical page.

[Brief explanation of the drawing]

FIG. 1 shows the structure of an embodiment of the present invention, and FIGS. 2 and 3 show the structure of a conventional address translation system. A......Logical address B...
・・・・・・Physical address a・・・・・・・・・・・・
・Virtual space number b・・・・・・・・・・・・Virtual page number C・・・・・・・・・・・・ Offset number in the page 1・・・・・・・・・・・・Pace register 2...
...Page table directory 3...
......Page table directory word 4.11.11'...Page table pointer 4'...Page table/Page table table pointer 5.5'...・Page table 6・・・・・・・・・Page table word 7・
・・・・・・・・・・・・Page pointer 8・・・・・・
・・・・・・Type bit 9・・・・・・・・・・・・
Page table table 10・・・・・・・・・・・・
Page table table word 13...
・・・Addition means 14・・・・・・・・・Register d1・・・・・・・・・Page table index d2・・・・・・・・・Page tennis Bull Table Index Representative Patent Attorney Satoshi Suyama - Figure 1 (Physical Address) B

Claims (2)

[Claims] (1) When converting a logical address including a virtual space number, virtual page number, and intra-page offset number into a physical address including a physical page number and intra-page offset number in physical space, multiple a word having a field indicating an intra-page offset number of the first entry of the first page of a page table arranged across a page area; and a page to which this word is indexed by the virtual space number in the logical address. a table directory, an addition means for adding an intra-page offset number in the word and a virtual page number in the logical address, and a position of each entry of the page table arranged in a plurality of page areas in the physical space. a page table table in which a word giving a field is indexed by the upper several bits of the addition result by the addition means, and a word having a field indicating the address of the page area is indexed by the lower several bits of the addition result by the addition means. An address translation method characterized by the provision of a page table. (2) The address conversion method according to claim 1, wherein the lower several bits of the addition result by the addition means are K bits. (However, K is a positive integer such that M = 2^KN, where the size of one page of the page table is M bits and the size of one word of the page table is N bits.)