JPH0652512B2 - Main memory page replay system - Google Patents

Description

The present invention relates to a main memory management system of a virtual memory computer system, and more particularly to a virtual memory computer system capable of setting a main memory page allocation limit frame for one task. Main memory page replacement method

[Conventional technology]

In a virtual memory computer system, conventionally, a main memory page allocation limit frame for one task is set to prevent a task requiring a large-scale virtual memory area from monopolizing the main memory resource of the system. It is suggested to do so. By the way, when the main memory page allocation limit frame is set for a certain task, the above task always operates in that state once the saturation state of the limit frame is once reached, so that every time a page fault interrupt occurs. It is necessary to select a releasable main memory page from the main memory pages assigned to the above task and replace it. At this time, if the selected main memory page has been updated, page unloading to the secondary memory device also needs to be performed.

As described above, when the main memory page allocation limit frame for a task is set, a page to be replaced must be searched and page unloading to the secondary memory device must be performed whenever a page fault interrupt occurs. However, there is a problem that the overhead becomes large.

In order to solve such a problem, when the allocation of main memory pages to a task reaches the limit frame, a fixed number of main memory pages that can be released from the main memory pages allocated to the task (for example, A method has been proposed in which selected main memory pages are collectively returned to the secondary storage device (for example, Japanese Patent Application No. 61-106506).
No.).

[Problems to be solved by the invention]

As described above, by collectively returning a plurality of main memory pages to the secondary memory device, it is not necessary to search for a replacement target page each time a page fault interrupt occurs, and the overhead can be reduced. However, since multiple pages are returned in a batch, the returned pages are unfortunately likely to be referenced again, and there is a problem that the number of times that the secondary storage device must be reloaded to the main storage device increases. .

The present invention solves the above-mentioned problems, and an object of the present invention is to reduce the overhead without increasing the number of reloads from the secondary storage device to the main storage device.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a virtual memory system having a paging mechanism and capable of setting a main memory page allocation limit frame for one task. When the limit frame is reached and the number of main memory pages of priority candidates for page replacement is less than or equal to a predetermined number, some main memory pages are selected from the main memory pages assigned to the task,
Regarding the selected main storage page, the content of the updated main storage page is reflected on the secondary storage device, and then it is made a priority candidate for page replacement.

[Work]

Some main memory pages are collectively set as priority candidates for page replacement, and are not returned.

〔Example〕

 Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, an embodiment of a virtual storage system to which the method of the present invention is applied is a main storage device 1 composed of a plurality of main storage pages 5, a secondary storage device 2, and a large-scale virtual storage device. Task 3 that requires bandwidth and paging controller 4
And a main memory page table 6 and a page table 7.

The main storage device 1 is physically divided into a plurality of main storage pages 5. The main memory page 5 includes an unused main memory page and a main memory page assigned to a task.

The paging control unit 4 includes a page allocation unit 41, a limit frame setting unit 42, a main memory page selection unit 43, an allocated page table 44, an allocated page management unit 45, and a register 46.
And an assigned page chain pointer 47.

The page allocating means 41 allocates an unused main memory page to the task 3 by adding a page absence interrupt. The limit frame setting unit 42 sets an allocation limit frame of the main memory page for task 3. In the allocated page table 44, the second
As shown in the figure, the reference bit, the update bit,
A plurality of LRU bits and pointer information are registered.

When the main memory page is allocated to task 3, the allocated page management means 45 registers the main memory page number in the allocated page table 44, and allocates the page chain pointer as pointer information corresponding to the registered main memory page number.
The content of 47 is registered, and the pointer information corresponding to the main memory page number registered last time is changed to the content indicating the main memory page number registered this time. Therefore, the main memory page allocated to the task 3 is managed by the allocated page chain 8 as shown in FIG. The allocated page chain pointer 47 points to the beginning of the allocated page chain 8. Further, the allocated page management means 45 sets the corresponding reference bit and update bit of the allocated page table 44 to “1” when the main memory page allocated to the task 3 is referred to and updated, and is allocated to the task 3. The corresponding update bit is set to “0” by reflecting the content of the main storage page of No. 2 in the secondary storage device 2. Further, the allocated page management means 45 periodically reflects the update bit in the LRU bit, and thereafter sets the update bit to "0".

The main memory page selection means 43 selects a certain number of main memory pages that have not been referenced recently from the main memory pages assigned to task 3 (for example, the number proportional to the limit frame), and selects the selected main memory page as The content of the updated main storage page is reflected in the secondary storage device 2 and then set as a priority candidate for page replacement. In the register 46, the number of remaining main memory pages that are priority candidates for page replacement is set.

As shown in FIG. 4, the main memory page table 6 stores the main memory page corresponding to the main memory page number assigned to the main memory page when the main memory device 1 is divided into main memory pages. A task identifier indicating which page of which task the existing page belongs to, and a status bit indicating whether or not a valid page is stored in the corresponding main memory page (“1” in this embodiment). = Valid, “0” = invalid) are registered.

In the page table 7, as shown in FIG. 5, the main storage device 1 of the main storage page in which a certain page is stored corresponding to the page number assigned to the page when the virtual storage area of task 3 is divided into pages. A main memory page address indicating the upper start address and a presence bit indicating whether or not the page exists in the main memory device 1 (in this embodiment, "1" = presence,
"0" = absent) is registered.

Next, the operation of the embodiment of the present invention will be described.

During the execution of the task 3, whether or not it exists in the page main memory 1 including the execution part of the task 3 is checked based on the existence bit of the page table 7, and if it does not exist, the page allocation means. A page fault interrupt is added to 41.

The page allocating means 41, after the execution of task 3 is started,
Until the number of pages of main memory set by the limit frame setting unit 42 is once assigned to the task 3, the main memory page table 6 is checked every time a page fault interrupt is added, and the status bit is "0". An unused main memory page is assigned to task 3, and then the process of setting the corresponding existing bit and status bit to "1" is repeated. In addition, the allocated page management means 45 registers the main memory page number of the main memory page in the allocated page table 44 every time the page allocation means 41 allocates the main memory page to the task 3, and changes the pointer information. The main memory page newly allocated to 3 is connected to the last part of the allocated page chain 8.

Then, after once allocating the main memory pages of the number of pages set by the limit frame setting unit 42 to the task 3, the page allocating means 41 issues a page fault interrupt notification to the main memory page selecting means every time a page fault interrupt is added. Add to 43. Upon receiving the above notification, the main memory page selection means 43 determines whether or not the number of main memory pages that are priority candidates for page replacement is less than or equal to a predetermined number (including 0) based on the contents of the register 46. Find out.

If the number of main memory pages that are priority candidates for page replacement is less than or equal to the predetermined number, the allocated memory area for task 3 is the main memory page in preparation for a page fault interrupt that occurs subsequently. Make a fixed number of main memory pages from among the priority candidates for page replacement. The method of making the main storage page in this embodiment a priority candidate for page replacement is as follows. That is, main memory page selection means
43 first refers to the allocated page table 44 and selects a fixed number of main memory pages that have not been referenced recently from the main memory pages allocated to task 3 based on the LRU bit. At this time, when the number of selected main memory pages does not reach the above-mentioned fixed number, the condition "not recently referenced" is relaxed (LRU is updated) and the selection is performed again, and the above-mentioned fixed number of main memory pages is selected. Reserve a memory page.

Next, the main memory page selection means 43 reflects the content (page image) of the updated main memory page among the selected main memory pages on the secondary memory device 2, and then sets the corresponding update bit to " 0 ". At this time, there are a plurality of updated main storage pages, and the secondary storage device 2
When the above continuous secondary storage area can be secured, the page images of the plurality of main storage pages are collectively reflected in the secondary storage device 2. With respect to the main storage page that has not been updated, the same page image exists in the secondary storage device 2, so it is not necessary to reflect the page image in the secondary storage device 2.

Next, the main memory page selecting means 43 changes the pointer information of the allocated page chain pointer 47 and the allocated page table 44 to change the selected main memory page to the allocated page chain 8 as shown in FIG. It is reconnected to the head of the page and positioned as a priority candidate when replacing the page. These main memory pages do not require LRU checking or page unloading to secondary storage,
It is ready for immediate replacement. FIG. 6 shows that the main memory pages with main memory page numbers P1 to Pn are priority candidates for page replacement. At this time, the main memory page selection means 43 sets the number of main memory pages that are priority candidates for page replacement in the register 46. By performing the above-described processing, a fixed number of main memory pages are set as priority candidates for page replacement.

Then, the main memory page selecting means 43 sets the page number of the main memory page linked to the head of the allocated page chain 8, that is, the page number of the main memory page pointed to by the allocated page chain pointer 47 to the page allocating means 41. Add. As a result, the page allocating means 41 allocates the main memory page corresponding to the page number added from the main memory page selecting means 43 to the task 3. At this time, the main memory page selection means 43 decrements the content of the register 46 in which the remaining number of page replacement priority candidates is set by -1 and changes the content of the allocated page chain pointer 47, thereby allocating Change the beginning of the page chain 8. For example, if the head of the allocated page chain 8 is P1 as shown in FIG.
As shown in the figure, P is assigned to the head of the allocated page chain 8.
It is changed to 2.

The main memory page selecting means 43, when the page absence interrupt notification is added from the page allocating means 41, if the number of main memory pages of the page replacement priority candidate is equal to or more than the predetermined number, the allocated page chain pointer is immediately assigned. The page number of the main memory page pointed to by 47 is added to the page allocating means 41, and thereafter, in the same manner as described above, the remaining number of priority candidates for page replacement is decremented by 1 and the allocated page is allocated. The content of the chain pointer 47 is updated. Therefore, the page-absence interrupt is processed at high speed while there are more than the predetermined number of page replacement priority candidates.

Further, when the main memory page which is the priority candidate for page replacement is referred to, the process of updating the existence bit of the page table 7 is not performed in the process of setting the main memory page as the priority candidate for page replacement. Therefore, the page is referred immediately without the occurrence of the page fault interrupt. At this time, the allocated page management means 45 changes the reference bit of the allocated page table 44 to “1”,
A process for removing the main memory page referenced by changing the pointer information from the page replacement priority candidates, and a register in which the number of remaining replacement priority candidates is set.
The contents of 46 are decremented by 1.

In the above-mentioned embodiment, the priority candidate for page replacement is connected to the head part of the allocated page chain, but it is also possible to set a dedicated page chain connecting only the main memory pages of priority candidates. It is possible.

〔The invention's effect〕

As described above, according to the present invention, in the virtual memory system, a part of the main memory pages allocated to the task operating in the saturated state of the main memory page allocation limit frame is set as a priority candidate for page replacement. When the number of main memory pages becomes less than a predetermined number, they are collectively set as priority candidates for page replacement, and a replacement target page is searched every time a page fault interrupt occurs. Since it is not necessary, there is an effect that overhead can be reduced. Further, since the main memory page that is the priority candidate for page replacement is made available for reference, even if the main memory page that is the priority candidate is referenced again. There is also the effect that there is no need to reload.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a configuration example of an allocated page table 44, FIG. 3 is a diagram showing a configuration example of an allocated page chain, and FIG. 4 is a main memory. FIG. 5 is a diagram showing a configuration example of page table 6, FIG. 5 is a diagram showing a configuration example of page table 7, FIG. 6 is a diagram showing a configuration example of an assigned page chain, and FIG. 7 is a configuration of assigned page chain. It is a figure which shows an example. In the figure, 1 ... main storage device, 2 ... secondary storage device,
3 ... Task, 4 ... Paging controller, 5 ... Main memory page, 6 ... Main memory page table, 7 ... Page table, 8 ...
... Allocated page chain, 41 ... Page allocation means, 42 ... Limit frame setting section, 43 ... Main memory page selection means, 44 ... Allocated page table, 45 ... Allocated page management means, 46 ... Register, 47 ... Allocated page chain pointer.

Claims (1)

[Claims] 1. In a virtual memory system having a paging function and capable of setting a main memory page allocation limit frame for one task, allocation of a main memory page for a task reaches said limit frame, and page replacement is performed. When the number of priority candidate main memory pages is less than or equal to a predetermined number, some main memory pages are selected from the main memory pages assigned to the task,
A main memory page replacement method characterized in that the selected main memory page is used as a priority candidate for page replacement after the content of the updated main memory page is reflected on the secondary memory device.