JPH07152652A - Virtual storage control method and information processor - Google Patents

Abstract

PURPOSE:To improve the throughput by determining an object page to be substituted for in a page substituting process of virtual storage in consideration of its process quantity and access frequency. CONSTITUTION:Respective pages (pages 0-n) used for the virtual storage are connected to a link queue. When the priority levels of pages that clear pointers 221-224 indicate are equal to priority levels set in the clear pointers, the reference bits of the pages are turned OFF. When the reference bit of a page specified with a substitution pointer is OFF at the time of the execution of page substitution, the page becomes an object of substitution. If the page whose reference bit is OFF is used before the substitution painter 220 reaches the page, the reference bit is turned ON, so the page is not substituted for. Clear points which are higher in priority is placed more close to the substitution painter, so the time required by the substitution pointer to reach a target page becomes short and the probability that the page becomes an object of substitution becomes high.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a virtual memory control method and an information processing apparatus for performing virtual memory control in page units.

[0002]

2. Description of the Related Art In an operating system of an information processing apparatus, data stored in a secondary storage device such as a magnetic disk is read into a RAM, and the CPU accesses the data in the RAM when processing the data. Virtual memory is used. . In this way, the RAM that can be accessed at high speed is accessed during data processing, and the number of accesses to the secondary storage device having a slow access speed is reduced to improve the processing speed.

Generally, an operating system of an information processing apparatus using virtual memory provides an area for virtual memory on the main memory and manages it in units of pages.
When more pages than the main memory are requested to execute the processing by the application program, the pages currently on the main memory are saved to the secondary storage device, and the pages are made available for the program to use. assign. This process is called page replacement. When the saved page is needed again, it is reloaded from the secondary storage device, page replacement is performed, and the page is used.

A method of deciding which of the pages in the main memory is to be the target of page replacement is called the page replacement method. Conventional information processing device operating system
As a page replacement method in the system, there is a method using the LRU algorithm.

In this method, a page to be replaced is selected based only on past usage history information of the page. That is, in the current operating system, the page subject to page replacement is LRU.
(Least Recently Used) Algorithm is selected according to an approximation method. This LRU algorithm leaves recently referenced pages in main memory and gives priority to the page that has not been referenced for the longest time, and uses the fact that application programs have temporal locality. Is.

[0006]

However, according to the above-mentioned method, the time required for the process of saving the data in the secondary storage device when it is the target of page replacement and the pages lost from the main memory due to the page replacement. The time required for the reloading process (the transfer process from the secondary storage device or the information processing device connected via the network to the main storage) when reusing is not taken into consideration. As described above, the conventional page replacement method proposed based on the assumption that the processing contents in executing the page replacement processing are equal in all pages has the following problems.

For example, if a page that has been rewritten on the main memory and has to be saved in the secondary storage device is replaced, the page is not rewritten on the main memory.
Compared to the case of replacing a page that does not need to be saved in the next storage device, page replacement in the secondary storage device requires extra processing. Also, when a page existing in a secondary storage device that takes a long time to read or an information processing device connected via a slow network is replaced with a page, a page existing in a relatively fast secondary storage device is replaced. It takes more time to reload when you have to use the page again than when you replace it.

As a countermeasure against the above-mentioned problems, a page which has not been written to the page and does not need to be saved in the secondary storage device or a page existing in the fast secondary storage device is preferentially given. Also, a page replacement method based on the processing time targeted for page replacement has been proposed.

In the above-mentioned method of giving page priority to each page and performing page replacement, a priority is set for each page, and a page replacement target is determined according to the priority. When setting the priority to the page in the program, the difference between the page whose content cannot be rewritten (code area) and the page whose content is rewritten (data area or stack area), and the device where the page exists Decide in consideration of processing speed.

However, the conventional page replacement method according to the priorities has the following problems. That is, since the page replacement target is always determined according to the set priority, the page with the highest priority is always the page replacement target. Therefore, even if a page is frequently accessed, if the priority is high, the page may be frequently replaced. As a result, such page replacement and reloading are repeated, and the processing efficiency of the information processing apparatus is reduced. Further, there is a problem of which page is selected as a replacement target from a plurality of pages having the same priority.

The present invention has been made in view of the above problems, and makes it possible to determine the target of page replacement based on the processing amount and access frequency generated by the page replacement processing of each page in virtual memory. An object of the present invention is to provide a virtual memory control method and an information processing device that realize improvement in processing efficiency.

[0012]

An information processing apparatus of the present invention that achieves the above object has the following configuration. That is, in an information processing device that controls a virtual memory function by a plurality of pages, the priority to be replaced in the page replacement process executed in the virtual memory function is set to a processing time that can occur during the replacement process. A setting means for setting each page based on each page, an extracting means for extracting one of a plurality of pages of the virtual memory function at the time of executing the page replacing process, and a page extracted by the extracting means. ,
A determination unit that determines whether or not the page has been accessed within a predetermined time based on the priority set by the setting unit, and a page replacement process that replaces the page when it is determined that the page has not been accessed by the determination unit. And executing means for executing.

Further, a virtual memory control method of the present invention for achieving the above object is a virtual memory control method for controlling a virtual memory function by a plurality of pages, the page being executed in the virtual memory function. A setting step of setting the priority to be replaced in the replacement processing for each page based on the processing time that may occur in the replacement processing, and a plurality of virtual memory functions that are provided at the time of executing the page replacement processing. An extracting step of extracting one of the pages, and a determining step of determining whether the page extracted by the extracting step has been accessed within a predetermined time based on the priority set by the setting step; And an execution step of executing a page replacement process with the page as a replacement target when it is determined that the page has not been accessed in the determination step.

[0014]

With the above structure, the priority of each page forming the virtual memory is set based on the processing time that may occur when the page is replaced. When page replacement processing is required in the virtual memory function, one of a plurality of pages forming the virtual memory is extracted, and it is determined whether the extracted page has been accessed within a predetermined time period past that point. judge. This predetermined time is set based on the priority of each page. For example, the higher the priority, the shorter the time. Then, if the page has not been accessed, the page replacement process is executed with the page as a replacement target.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram of an information processing apparatus according to this embodiment. In the figure, reference numeral 1 is a CPU, which controls the apparatus. A main memory 2 is composed of a ROM 201 and a RAM 202. The ROM 201 stores various programs and data executed by the CPU 1.
Note that the ROM 201 also stores a control program for realizing the processing described in each flowchart described later. The RAM 202 is used as a storage area for various information and programs loaded from the secondary storage device 3 and a work area for the CPU 1. The virtual storage area is also R
It is provided in AM202. A secondary storage device 3 stores various data and programs.
There are two types of secondary storage devices, a local disk owned by the information processing apparatus and a remote disk accessible via a network (see FIG. 2). Reference numeral 4 denotes a keyboard as an input device, which inputs various data and the like. Reference numeral 5 denotes a display device on which a result processed by the CPU 1 and the like are displayed. 6 is a network, I /
It is connected to the CPU 1 via an O interface (not shown).

FIG. 2 is a block diagram for explaining the operation of the virtual memory function in this embodiment. RAM in main memory 2
A virtual storage area of page 0 to page n for n + 1 pages is provided on 202. In the figure, the area of page 0 stores data from the remote disk 32 connected via the network 6, and the area of page 3 stores data of the local disk 31. Then, each of these pages in the virtual storage area is managed by the page management table 210.

FIG. 3 is a diagram for explaining the data structure of the page management table 210. In the figure, page 211
Is information for specifying each page of page 0 to page n. The priority 212 is information indicating the priority in page replacement, and in this example, it is divided into four stages (1) to (4). The priority of page replacement will be described later. The reference bit 213 is a bit indicating whether each page is used by the CPU 1. The function of the reference bit will be clarified later in the description.

Next, the operation of the information processing apparatus of this embodiment having the above configuration will be described.

FIG. 4 is a flow chart showing the outline of the operation of this embodiment. In step S21, a page replacement priority is set for each assigned page. This priority reflects whether the page must be written to secondary storage when it becomes the replacement target, and how much processing time it takes to reuse the content held by the page. Is set.

FIG. 5 is a diagram showing an example of priority setting. The page with the highest priority as the target of page replacement is the page that holds the file on the local disk 31 and is not rewritten, and this is referred to as priority (4). Network 6 has the next highest priority
There is a page that holds a file on the remote disk 32 connected above without rewriting, and this is set as priority (3). The next highest priority is a page that holds a file on the local disk 31 and is rewritable, and this is referred to as priority (2). The page with the lowest priority is the page that holds the file on the remote disk 32 connected to the network 6 and is rewritten, and this is set as the priority (1).
Then, the priority thus determined is registered in the priority 212 of the page management table 210.

In this example, the priority is set assuming that the access speed of the local disk 31 is faster than the access speed of the remote disk 32. Various patterns of these priorities can be considered depending on the network 6 used, the type of the secondary storage device 3 connected, and the like. Further, the setting of the priority does not necessarily have to be performed at the time of page allocation, and can be dynamically set at the time of determining the page replacement target or at the time of executing the program. By dynamically setting the priority, for example, for a rewritable page, the priority of a page that has actually been rewritten can be set lower than the priority of a page that has not been rewritten. Thus, by setting the priority dynamically, it is possible to set the finer priority.

Next, in step S22 of FIG. 4, the page allocated to the virtual storage area is used. At this time, the reference bit 213 of the used page in the page management table 210 is turned on. And step S2
If page replacement is required in 3, the replacement target is selected by the method described below.

A method of selecting a replacement target, which is a characteristic operation of this embodiment, will be described below. Needless to say, when an unused page remains, that page is used.

FIG. 6 is a diagram for explaining the concept of the method of selecting the replacement target page in this embodiment. Each page (page 0 to page n) used for virtual storage is connected to the ring queue. And one of these pages
The replacement pointer 220 and each of the clear pointers (221 to 221) to which priority 1 to priority 4 are set
224). The replacement pointer 220 is a pointer for determining the target of page replacement, and the clear pointer 2
Reference numerals 21 to 224 are pointers for turning off the reference bit. The clear pointers 221 to 224 are arranged closer to the replacement pointer 220 as the priority of the clear pointers 221 to 224 is higher.

FIG. 7 is a flow chart for explaining the operation and function of the replacement pointer 220 and the clear pointers 221 to 224 of FIG. When the number of unused pages in the virtual recording area becomes less than a predetermined amount or when there are no more unused pages, the system calls the processing shown in the flowchart of FIG. 7 at regular intervals.

In step S31, the replacement pointer 2
20 and each of the clear pointers 221 to 224 are advanced by one page. In step S32, the priority of the page pointed to by one clear pointer is compared with the priority set in the clear pointer. If they are not equal, the process directly proceeds from step S33 to step S35. On the other hand, when both are equal (for example, the priority of the page pointed to by the clear pointer 221 is (1))
Advances from step S33 to step S34, and the reference bit 21 of the corresponding page in the page management table 210
Turn off 3. In step S35, it is determined whether or not all the priorities are completed, that is, all clear pointers 221 to 221.
224 from step S32 to step S3 described above.
It is determined whether or not the process of 4 is performed. Then, if it has not been completed, the process returns to S32, and if it has been completed, this processing ends.

As described above, the replacement pointer and each clear pointer are advanced one by one and the reference bit of each page is updated every predetermined period. When page replacement is required while performing such processing, the page to be replaced is determined according to the flowchart shown in FIG. 8 and page replacement is executed.

FIG. 8 is a flowchart showing a procedure for selecting a page to be replaced in page replacement. In step S41, the reference bit of the page pointed to by the page replacement pointer is checked. Then, if the reference bit is turned on, the process proceeds from step S42 to step S43, the page is determined as a replacement target, page replacement is executed, and this processing ends.

On the other hand, if the reference bit is not turned on, the process advances from step S42 to step S44 to advance the replacement pointer 220 and the clear pointers 221 to 224 one by one. Then, in steps S45 to S47, the processes of steps S33 to S35 described above are performed to update the reference bit. And step S
Returning to step 41, the reference bit is newly checked for the page newly designated by the replacement pointer 220, the replacement target selection processing is performed, and this is repeated until the replacement target is determined.

As described above, when the page replacement process becomes necessary, if the reference bit of the page pointed to by the replacement pointer is off at that time, the page is selected as the replacement target. On the other hand, when the page is accessed after the reference bit is turned off by the operation of the clear pointer, the reference bit is turned on by the process of step S22. Therefore, the reference bit of the page pointed to by the replacement pointer may be turned off when the page replacement process is required. In such a case, the page is not set as the replacement target, the replacement pointer and each clear pointer are advanced to update the reference bit, and the selection process of the replacement target page is continued.

Next, regarding the selection of the page to be replaced in this embodiment, how the usage frequency and priority of each page are reflected will be described.

Since the clear pointer is located ahead of the replace pointer in the ring queue, it takes a certain time for the replace pointer to reach the page. When a page is referred to within this fixed time, the reference bit is turned on, so that page is not replaced. in this way,
Whether or not the page is used within a predetermined time is reflected in the selection of the replacement target page.

Further, in order to replace a page having a high priority with a high probability, the clear pointer having a high priority is placed at a position close to the replace pointer, and the clear pointer having a low priority is placed at a position far from the replace pointer. . This shortens the period from when the reference bit is turned off to when the high priority page is designated and checked by the replacement pointer, and therefore has a high probability of being replaced.
The priority is reflected.

In the above example, all the pointers are advanced one page at a time, but it is also possible to check the reference bit by the replacement pointer, replace the page, and clear the reference bit by the clear pointer a plurality of times at a time. is there.

As described above, by using the page replacement method of the present embodiment, a page having a small processing amount for the saving process and reloading process at the time of page replacement is preferentially targeted for page replacement. This has the effect of shortening the overall page replacement processing time of the information processing apparatus. Further, it becomes possible to select pages with low priority as replacement targets to some extent without selecting only pages with high priority as replacement targets. For this reason, it is possible to prevent frequent page replacement and reloading due to, for example, replacement of a page having a high use frequency and a high priority, so that the processing efficiency of the entire information processing apparatus is improved. Further, among pages having the same priority, pages to be replaced are selected approximately according to the LRU. Therefore, pages having a high priority of page replacement and infrequently used are replaced first and the processing efficiency is improved. .

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can also be applied to a case where it is achieved by supplying a program that causes a system or an apparatus to execute the processing defined by the present invention.

[0038]

As described above, according to the present invention,
The page replacement target page can be determined in consideration of the processing amount and access frequency generated by the page replacement processing of each page in the virtual memory, and the processing efficiency is improved.

[0039]

[Brief description of drawings]

FIG. 1 is a block diagram of an information processing apparatus according to an embodiment.

FIG. 2 is a block diagram illustrating an operation of a virtual memory function in this embodiment.

FIG. 3 is a diagram illustrating a data configuration of a page management table.

FIG. 4 is a flowchart showing an operation outline of the present embodiment.

FIG. 5 is a diagram showing an example of setting priorities.

FIG. 6 is a diagram illustrating a concept of a method of selecting a replacement target page in the present embodiment.

FIG. 7 is a flowchart illustrating operations and functions of a replacement pointer and clear pointers.

FIG. 8 is a flowchart showing a procedure for selecting a page to be replaced in page replacement.

[Explanation of symbols]

 1 CPU 2 Main Memory 3 Secondary Storage Device 4 Keyboard 5 Display Device 6 Network 201 ROM 202 RAM

Claims (8)

[Claims] 1. An information processing apparatus for controlling a virtual memory function by a plurality of pages, wherein a priority to be replaced in a page replacement process executed in the virtual memory function can occur during the replacement process. Setting means for setting each page based on processing time; extraction means for extracting one of a plurality of pages of the virtual memory function at the time of executing the page replacement processing; and extraction means for extracting by the extracting means. A determination unit that determines whether the page has been accessed within a predetermined time based on the priority set by the setting unit, and when the determination unit determines that the page has not been accessed, the page is set as a replacement target. An information processing apparatus comprising: an execution unit that executes page replacement processing. 2. The processing time that can occur during the replacement processing in the setting means is, when a page is targeted for replacement,
2. The information processing apparatus according to claim 1, wherein the processing time is a processing time required for saving processing to the secondary storage device when replacing the page and a loading processing when reusing the page. 3. The information processing apparatus according to claim 1, wherein the predetermined time in the determination unit is shorter for a page having a higher priority set by the setting unit. 4. The information processing according to claim 1, wherein when the determination unit determines that the page is being accessed, the extraction unit, the determination unit, and the execution unit are repeated for another page. apparatus. 5. An information processing apparatus for controlling a virtual memory function by a plurality of pages, wherein a priority to be replaced in a page replacement process executed in the virtual memory function can occur during the replacement process. Setting means for setting each page based on processing time; a first pointer for sequentially designating the plurality of pages; and a plurality of pages prior to the first pointer and in descending order of the priority. Pointer control means for controlling a plurality of second pointers sequentially designated; and, for each of the pages designated by the plurality of second pointers, the priority set for the page and the second pointer designating the page. When the corresponding priorities are equal, starting means for starting a check for the presence or absence of access to the page, and when executing the page replacement process, Note: Extraction means for extracting a page designated by the first pointer, and page replacement with the page extracted by the extraction means as a replacement target when it is determined that the page extracted by the extraction means is not accessed in the investigation started by the start means. An information processing apparatus comprising: an execution unit that executes a process. 6. A virtual memory control method for controlling a virtual memory function by a plurality of pages, wherein priority to be replaced in a page replacement process executed in the virtual memory function is generated during the replacement process. A setting step of setting each page based on the obtained processing time; an extraction step of extracting one of a plurality of pages of the virtual memory function at the time of executing the page replacement processing; and an extraction step of the extraction step. The determined page determines whether or not the page has been accessed within a predetermined time based on the priority set by the setting step, and replaces the page when it is determined not to be accessed by the determination step. And a step of executing page replacement processing as described above, and a virtual memory control method. 7. The virtual memory according to claim 6, wherein when it is determined by the determination step that the page is being accessed, the extraction step, the determination step, and the execution step are repeated for another page. Control method. 8. A virtual memory control method for controlling a virtual memory function by a plurality of pages, wherein a priority to be replaced in a page replacement process executed in the virtual memory function is generated during the replacement process. A setting step for setting each page based on the obtained processing time; a first pointer for sequentially designating the plurality of pages; and a plurality of pages preceding the first pointer and in descending order of the priority. A pointer control step of controlling a plurality of second pointers sequentially designating, and, for each of the pages designated by the plurality of second pointers, a priority set for the page and a second pointer designating the page. When the corresponding priorities of the above are the same, the start step of starting the investigation of the presence or absence of access on the page, and An extraction step of extracting a page designated by the first pointer, and a page subject to replacement when it is determined that the page extracted by the extraction step is not accessed in the investigation started by the start step A virtual memory control method comprising: an execution step of executing a replacement process.