JPH0573425A - Address converting system for virtual computer - Google Patents

Abstract

PURPOSE:To attain high speed access by executing an instruction in an instruction table, and executing an access of data to a real memory address space. CONSTITUTION:A code 4 tries to read out (fetch) data from an address (a) on a virtual address space 1, calculates the number of pages (a1) of the address (a), jumps to a call map table 3 in which its (a1) is an index and transfers the control. In the call map table 3, a processing corresponding to a flag of the map table is written by an internal code, and by executing an instruction of this internal code, an access of data to a real memory address space 2 is executed. In the case a regular access can be executed, a real address is included in the internal code and set to a pointer to be accessed finally. Accordingly, the call map table 3 corresponding to the map table is executed as a code stream.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an address conversion system for executing memory access at high speed when a virtual machine is realized on a general-purpose operating system (hereinafter referred to as OS).

[0002]

2. Description of the Related Art An access method in a conventional virtual computer will be described with reference to FIG. In the figure, 11 is a virtual address space to be accessed, 12 is a real address space, 13 is a map table which is a conversion table from a virtual address to a real address, and 14 is a code part for performing an access operation in a virtual computer. First, when the code 14 attempts to read data from the address a in the virtual address space 11 (Fetch), the page number a1 of the address a is calculated, and the entry having the index a1 is fetched from the map table 13. The entry includes a real address base and a flag expressing the state of the page number a1. In the code 14, the flag portion is taken out by masking from the drawn entry, and branching is made to the exception processing (14 ') such as page fault and the normal access processing by the conditional branch. Further, at the actual access stage, the real address is calculated from the real address base and the in-page offset from the map table 13 to access the memory.

Since the virtual computer here is intended to operate a wide range of machines, the access method depending on a specific OS is not adopted, and the virtual computer defines the use related to access and executes the virtual computer. The virtual image that is the environment is intended to be machine independent. Therefore, the access method is unique to the virtual machine.

[0004]

As described above, providing the access method independently without depending on the machine means that the versatility is improved and the execution environment of the virtual machine can be easily ported to various OSs. .. However, in the conventional access method, there was inevitably an overhead that information on each page had to be fetched for each access (until now, page information was accessed as that overhead and necessary flags were masked. I was taking it out. Further, in order to obtain the real address of the virtual computer, it is necessary to add the start address of the virtual space of the virtual computer on the real computer, which causes the decrease in access speed.

It is an object of the present invention to provide a virtual computer address conversion method capable of increasing the access speed without changing the upper layer such as the virtual environment at all.

[0006]

In order to solve the above-mentioned problems, in the address conversion system of a virtual computer according to the present invention, a virtual memory address space to be a memory access target, a real memory address space, and a memory access operation. And an instruction table having an instruction sequence prepared as a substitute for a flag expressing the state of each page of the virtual memory address space as an entry, and executing the instructions in the instruction table, Normal access processing or fault processing for the real memory address space is performed.

In the above-mentioned processing, if the page corresponding to the corresponding address is in the normal state and accessible, the RET is stored as an instruction string in the slot in the instruction table.
Perform the process of writing the URN. If the page state corresponding to the corresponding address is changed by the access, the access is performed and the internal code of the instruction table is rewritten, and a new instruction corresponding to the flag expressing the page state is made in the next access. I'm trying to run a column. Further, the real address corresponding to the corresponding address is written as an instruction string or as a constant in an instruction table having an instruction string as an entry, and is used as a base address for access.

[0008]

When the data is accessed from the virtual memory address space by the code section, the page number is calculated from the address in the virtual memory address space, and the control is transferred to the instruction table indexing the value. An instruction sequence corresponding to each page is written in the entry of the instruction table, and by executing this instruction sequence, preset processing and processing of rewriting the internal code of the instruction table are executed. .. Therefore, it is not necessary to perform a mask for fetching the real address from the map table and a conditional branch for determining the state of the flag as in the conventional case, so that the overhead associated with the memory access operation can be reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an address conversion system for a virtual computer according to the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a virtual computer to which the address conversion system according to the present invention is applied. In the figure, 1 is a virtual address space to be accessed, 2 is a real address space, 3 is a call map table which is an instruction table having an instruction sequence corresponding to each page as an entry,
Reference numeral 4 is a code portion for performing a memory access operation.

As an operation at the time of memory access, first, when the code 4 attempts to read data from the address a in the virtual address space 2 (Fetch), the page number a1 of the address a is calculated and the a1 is used as an index. Then, the control jumps to the call map table 3 and the control is transferred. The call map table 3 includes the map table 1 shown in FIG.
The processing corresponding to the flag of No. 3 is written in the internal code, and the data is accessed to the real memory address space 2 by executing the instruction of this internal code.

When it is normally accessible, the real address is included in the internal code and set to the pointer to be finally accessed (real address constant set). When a page fault occurs, write it as a jump instruction to the fault in the call map as an internal code. As a result, the call map table 3 corresponding to the map table is executed as a code stream, so that in a processor equipped with an instruction cache, the call map table fits in the instruction cache and higher speed can be expected. Also, by adopting this method, it becomes possible to replace the contents of the map table with an instruction sequence. That is, the map table 13 (FIG. 4)
In situations where you have to update the flags in
The instruction sequence in the call map table 3 can be substituted by rewriting its own internal code.

FIG. 2 shows this state. The flag f in the map table is referenced, dir
There are three types, ty and protected. re
“Ferenced” represents that the corresponding page has been accessed at least once. Dirty represents that writing has been performed on the corresponding page. Further, protected indicates that the corresponding page is write protected, and a fault occurs when a write operation is performed. When the virtual page is not assigned to the real page (Vacant), for the sake of convenience, the dirty and prote
Set cted so that it can be expressed. In addition, two slots (Fetch, St) of the call map table
The contents of the entry are written in (ore). The description below the slot expresses the state (flag) of the page.

In the address conversion method based on the call map table, slots are prepared and processed for reading (Fetch) and writing (Store) as described above. For example, in reading, an entry in the call map table on the reading side is executed, and if the corresponding page is accessed first,
It overwrites its own internal code with the instruction to set the real address and the RETURN instruction (state 2 to state 3). In other words, if the code for rewriting itself is not set, the referenced is not set, and if the code for rewriting itself is set, it indicates that the referenced is set. In writing, if the code to rewrite itself is not set, dir
If ty is not set and the code that rewrites itself is set, then dirty is set (state 3 to state 4, or state 2 to state 4). Further, the call map table corresponding to the state where protected is set sets an internal code such that the call map table on the writing side jumps to a fault regarding writing (state 2
Or 3 to state 5). When the virtual page is not assigned to the real page, the call map entry is changed to jump to the page fault processing on both the reading side and the writing side (states 2 to 5 to state 5).

In the case of a memory access operation which does not cause a fault, the base address of the real page is set in a register and set to RETURN. Specifically, the real address of the virtual computer is the general-purpose O on which the virtual computer appears.
When it is expressed in S as shown in FIG. 3, by setting "real address base value" + "real address space base address value on general-purpose OS"-"virtual address base value" in the register, For all accesses within the page, the address can be directly addressed using the corresponding register as a pointer. As a result, it is not necessary to perform masking for fetching the real address from the map table and conditional branching for determining the state of the fetch flag using the mask as in the conventional method. Therefore, these overheads can be reduced.

By the way, by using the above address conversion method on the virtual computer, it was possible to improve the speed by about 40% in the Dhrystone benchmark test.

[0017]

As described above, in the address conversion method for the virtual computer according to the present invention, the state of each page in the virtual memory address space is expressed instead of the conversion table from the virtual memory address to the real memory address. The instruction table with the prepared instruction sequence as a substitute for the flag is provided, and the data in the actual memory address space is accessed by executing the instructions in the instruction table. Do masks to take it out,
It is not necessary to perform conditional branching in order to judge the state of the fetch flag using a mask as a mask, and the process of adding the amount of offset within the page is not necessary. Therefore, the access speed can be increased without changing the upper layer such as the virtual environment at all.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a virtual computer to which an address conversion method according to the present invention is applied.

FIG. 2 is a diagram showing the contents of a map table and a call map table.

FIG. 3 is a diagram showing how a real address of a virtual computer is expressed on a general-purpose OS on which the virtual computer is mounted.

FIG. 4 is a diagram showing a configuration of a virtual computer to which a conventional address translation system is applied.

[Explanation of symbols]

1 ... Virtual address space, 2 ... Real address space, 3 ... Call map table, 4 ... Code, 13 ... Map table

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akiko Ohashi No. 100-1 Sakado, Takatsu-ku, Kawasaki-shi, Kanagawa KSP R & D Business Park Building, Fuji Xerox Co., Ltd.

Claims (1)

[Claims] 1. A substitute for a virtual memory address space that is a target of memory access, a real memory address space, a code section that executes a memory access operation, and a flag that expresses a state of each page of the virtual memory address space. With an instruction table that uses the prepared instruction sequence as an entry,
An address conversion method for a virtual machine, characterized in that data in an actual memory address space is accessed by executing an instruction in the instruction table.