JPH03235148A - Computer system - Google Patents

Abstract

PURPOSE:To efficiently execute page management by selecting a page to be written back from a memory device to a disk device considering the state of every kind of memory device in a computer system, especially, the state of a TLB (address conversion buffer) device. CONSTITUTION:When the page on the memory device 42 is written back to the disk device 43, the page to be written back is selected considering the state of every of memory device of the computer system such as the TLB device 41, etc. As a result that the write back of the page is performed especially considering the state of the TLB device 41, the number of times to issue a nullifying request to the TLB device 41 can be reduced. In such a way, the page management of the computer system which performs virtual memory management is executed at high speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a computer system that performs paging-based virtual memory management.
etc., regarding a page management method that takes into consideration various states of a computer system.

[Conventional technology]

A TLB device is a device that stores a part of a page table existing on a memory device and converts a logical page number into a physical page number at high speed. Note that the internal structure and system of the TLB device are not directly related to the present invention, so explanations thereof will be omitted.

In conventional page management methods, when writing a page on a memory device back to a disk device, the target page is determined by considering whether it has not been referenced for a certain period of time in the past or how long it has not been referenced. Ta.

For this reason, a "reference bit" as shown in FIG. 3 has been provided in the page table entry indicating the correspondence between the logical page number and physical page number of the virtual memory. When a processor refers to a memory device during instruction execution, the most significant reference bit in the page table entry corresponding to the reference position is set to 1. This bit is shifted downward at regular intervals. If all the reference bits become O, this indicates that this page has not been referenced for a certain period of time.
The page will be written back to the disk device as an unnecessary page.

The above method is disclosed in Japanese Patent Laid-Open No. 63-259749.

[Problem to be solved by the invention]

In the conventional method as described above, when a page on a memory device is written back to a disk device, the only factor for selecting a page to be written back is - the length of unreferenced time. However, there are various factors for selecting pages to be written back.

Specifically, there are the states of the TLB device and cache storage device. The factors that determine whether or not to write back a page on the memory device to the disk device are: ``Does the TLB device store the correspondence between the logical page number and physical page number of the page?'' ``Does the data of the page match?'' We also want to consider things like whether there are a lot of them in the cache storage device.

In particular, when writing a page on a memory device back to a disk device, the TLB device must always invalidate the entry corresponding to the page (it does not have a function to invalidate individual entries). , some TLB devices require all entries to be invalidated). In general, the overhead associated with invalidation is large. In particular, in a multiprocessor type computer system having multiple processors, an invalidation request (this generally takes the form of a processor open interrupt) is issued to the TLB device present in all processors, resulting in overhead. becomes even larger.

Furthermore, in the case of a page stored in an entry of a TLB device, it is predicted that much of that data also exists on the cache storage device, so it is very important to consider the state of the TLB device.

An object of the present invention is to select a page to be written back from a memory device to a disk device by taking into account the states of various storage devices in a computer system, especially the state of a TLB device, and to improve efficiency in paging-based virtual memory management. It is to perform proper page management.

[Means to solve the problem]

The above purpose is to create a storage field in a page table entry that indicates whether each storage device of the computer system stores control information and data for the corresponding page, or a storage amount field that indicates the amount of data stored. This is achieved by creating a page and using it for page management.

When managing pages with consideration to the state of the TLB device, a TLB that indicates which processor's TLB device the entry is stored in is included in the page table entry.
This is achieved by providing an LB specification field or a TLB reference bit indicating that any TLB device stores it, and using this to perform page management.

[Effect]

The storage field sets a value when the corresponding storage device reads the control information and data of the corresponding page,
If the read control information and data are discarded,
Reset the value.

The storage amount field increases in value when the corresponding storage device reads control information and data of the corresponding page, and decreases in value when the read control information and data are discarded.

The TLB specification field is set with information when a TLB device of a certain processor reads and stores the corresponding page table entry.

In addition, when a request to invalidate an entry is made to the TLB device, and when an entry in the TLB device is replaced with another entry, the TLB specification field corresponding to the entry to be invalidated/replaced is Sets the entry not to be remembered.

The TLB reference bit is set when any TLB device reads the entry, and reset when an invalidation request occurs.

In the page management method that takes into consideration the TLB device of the present invention, if there are not enough unused empty pages on the memory device, the TLB specification field or the TLB reference bit is checked, and page table entries are stored in the TLB device. The page that is written back from the memory device to the disk device is determined by two factors: whether the page has been referenced or not, and the length of time that the corresponding page has not been referenced (measured using reference bits in the conventional method). , invalidate the TLB device.

〔Example〕

Embodiments of the present invention will be described using the drawings.

FIG. 3 shows the inside of a page table in a conventional page management system. 10 is a page table,
11 indicates one entry of the page table. Inside the entry 11, there is a correspondence between a logical page number 30 and a physical page number 31. For logical page numbers that do not exist in the TLB device, address translation is performed by checking this correspondence.

Reference bit 32 indicates whether or not the data of the corresponding page has been referenced within a certain period of time in the past.

When the data in the page is referenced, the most significant bit of the reference bit 32 is set to 1. Thereafter, the reference bit 32 is shifted to the lower order at regular time intervals. When the contents of the reference bits 32 are all 0, the page corresponding to that entry is classified as an unnecessary page. In the following embodiments of the present invention, the concept of the reference bit 32, which has been used conventionally, and an outline of unnecessary pages classified by the concept will be used.

FIG. 1 shows the internal structure of a page table 10 for carrying out the page management method of the present invention. Within entry 11 of the page table are TLB storage fields 12 . A cache storage amount field 13 and the like exist. This is a field indicating whether the various storage devices of the computer system store the control information and data of the corresponding page, or.

This field indicates the amount stored. If it is the former field, a value is set when the corresponding storage device reads out the control information and data of the corresponding page. When the read control information and data are discarded, the values are reset. If it is the latter field, the value is increased when the corresponding storage device reads out the control information and data of the corresponding page. When the read control information and data are discarded, the value is decreased. In the page management method of the present invention, each field of the above page table is referred to to determine the page to be written back from the memory device to the disk device.

Although the above embodiment considers only the states of the TLB device and cache storage, it is also possible to provide storage fields and storage amount fields for other storage devices of the computer system.

In the following embodiment of the present invention, only a page management method that takes into consideration the TLB device, which is the most important in page management, will be explained.

FIG. 2 shows the internal configuration of the page table 10 for managing pages in consideration of the state of the TLB device in the present invention.

Figure 2 (1) shows that T is inside entry 11 of the page table.
This configuration includes an LB designation field 20. The TLB designation field 20 indicates which processor's TLB device stores the corresponding entry in the page table. T
The LB designation field 20 has the same number of bits as the number of processors.

If each bit is 1, the TL of the corresponding processor
This indicates that the corresponding entry is stored in the B device, and if the bit is O, it indicates that it is not stored. T.L.
According to the B designation field 20, claim 10
Classification of strongly restricted pages and weakly restricted pages in paragraphs to 12,
In addition, it is possible to select a page device to be invalidated when writing back a strongly restricted page to a disk device.

Figure 2 (2) shows that T is inside entry 11 of the page table.
This is a configuration in which an LB reference bit 21 is provided.

TLB reference bit 21 is the TLB of one of the processors.
Indicates that the device has stored the corresponding entry in the page table. If the TLB reference bit is 1, it indicates that the corresponding entry is stored in the TLB device of any processor, and if the bit is O, it indicates that the entry is not stored in any TLB device. The bits enable the above-mentioned classification of pages with strong restrictions and pages with weak restrictions.

Figure 9 shows the TLB specification field and TL shown in Figure 2.
A state transition diagram when using B reference bits is shown.

FIG. 9(1) is a state transition diagram of each bit of the TLB designation field 20. Each bit corresponds to the T of the corresponding processor.
Set to 1 if the LB device reads the entry. Furthermore, when switching virtual spaces or writing the corresponding page back to the disk device, the entry in the TLB device is invalidated.

At this time, the TLB specification field is reset to O. Further, the bit is also reset to O when the TLB device evicts the corresponding entry and reads another entry.

FIG. 9(2) is a state transition diagram of the TLB reference bit 21. The TLB reference bit is the TLB of either processor.
Set to 1 if the device has read the entry. Furthermore, when switching virtual spaces or writing the corresponding page back to the disk device, the entry in the TLB device is invalidated. At this time, the TLB specification field is reset to 0.

FIGS. 4 and 5 show conceptual diagrams of the page management system according to claims 10 to 12 of the present invention. Fourth
The figure corresponds to claim 10, and FIG. 5 corresponds to claims 11 and 12.

FIG. 4 is a conceptual diagram of the first embodiment of the page management system of the present invention. A processor 40 includes a TLB device 41 that performs address translation.

42 is a memory device, 43 is a disk device, and these two
A virtual space is constructed by people. 44 is a communication bus, and processor 40. Memory device 42° disk device 43
Combine each. A page table 10 exists inside the memory device. The page table 10 shows the correspondence between logical page numbers and physical page numbers, as in the past. Note that a part of the page table is stored in the TLB device 41.

In the first embodiment of the page management method of the present invention, when writing a page on the memory device 42 back to the disk device 43,
First, all pages of the memory device 42 are classified into empty pages 45a that are not used, unnecessary pages 45b that are not empty pages but have not been used for a certain period of time, and pages that are neither of these pages. Determination as to whether the page is an empty page is made based on whether or not the page number correspondence is stored in the page table. Whether or not a page is an unnecessary page is determined using reference bits as in the conventional case. Furthermore, the unnecessary page 45b is classified into a strongly restricted page 45c whose page number correspondence is stored in the TLB device, and a weakly restricted page 45d which is not stored in the TLB device.

The page management means first writes back the weak restriction page 45d to the disk device 43, making it an empty page. As a result, if the number of empty pages does not exceed the minimum value, the hard limit page 4
5c is written back to the disk device 43.

FIG. 6 shows an algorithm for the page management method in the first embodiment of the present invention.

A conceptual diagram of the second embodiment of the page management method of the present invention is shown in FIG.
As shown in the figure. The overall system configuration is the same as that shown in FIG. In the second embodiment, when writing pages on the memory device 42 back to the disk device 43, all pages in the memory device 42 are first classified into unused empty pages 45a and non-empty pages. Whether or not a page is an empty page is determined based on whether or not the page number correspondence is stored in the page table. Furthermore, non-empty pages are classified into strong restriction pages 45c whose page number correspondence is stored in the TLB device, and weak restriction pages 45d which are not stored in the TLB device. The page management means first writes back to the disk device 43 among the weakly restricted pages 45d in descending order of the pages that have not been referenced for a long time, making them empty pages. As a result, if the number of empty pages does not exceed the minimum value, the pages of the strongly restricted pages 45c are written back to the disk device 43 in the order of pages that have not been referenced for a long time.

Note that the smaller the number represented by the reference bits in the conventional system, the longer the time during which they are not referenced.

FIG. 7 shows an algorithm for the page management method in the second embodiment of the present invention.

The conceptual diagram of the third embodiment of the page management method of the present invention is also shown in the fifth embodiment.
It will be the same as the figure. In the third embodiment, when writing back pages on the memory device 42 to the disk device 43, all pages in the memory device 42 are first classified into unused empty pages 45a and non-empty pages. Determination as to whether the page is an empty page is made based on whether or not the page number correspondence is stored in the page table. Furthermore, non-empty pages are classified into strong restriction pages 45c whose page number correspondence is stored in the TLB device, and weak restriction pages 45d which are not stored in the TLB device. The page management means first adds a constant value to the reference bit of the strongly restricted page 45c. Thereafter, among the pages that are not empty, the pages are written back to the disk device 43 in order from the page with the smallest number represented by the reference bit to become an empty page. It should be noted that if the value added to the reference bit is too large, the second embodiment of the present invention will be used, and if the value added is O, the method will be the conventional method.

FIG. 8 shows an algorithm for the page management method in the third embodiment of the present invention.

With the above page management method, it is possible to reduce the number of times a strongly restricted page is written back to the disk device, and to reduce the number of TLB invalidations. This can improve the performance of both single-processor and multi-processor systems, but in the case of multi-processor systems, the following effects can be obtained.

In a multiprocessor system, when a page is written back to a disk device, the TLB of the processor in charge of writing back is
It is necessary to invalidate not only the device but also the TLB devices of other processors. The method of invalidation usually takes the form of temporarily stopping the program running on the target processor and requesting the processor itself to invalidate it. For this reason, processor open interrupts are often used. By using the page management method of the present invention, it is possible to avoid wasteful processor open interrupts and associated processing (such as saving and restoring registers) as much as possible. There is no need to interrupt programs that are essentially unrelated to the page being written back to the disk device.

〔Effect of the invention〕

According to the present invention, when a page existing on a memory device is written back to a disk device, the states of various storage devices of the computer system, such as a TLB device, are taken into consideration.

You can select which pages to write back. In particular, by writing back pages in consideration of the state of the TLB device, it is possible to reduce the number of times invalidation requests are made to the TLB device.

This makes it possible to perform page management at high speed in a computer system that performs virtual memory management.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a page table for supporting the page management method of the present invention, FIG. 2 is a configuration diagram of a page table for supporting the page management method based on the state of the TLB device of the present invention, FIG. 3 is a configuration diagram of a page table in the conventional method, FIG. 4 is a conceptual diagram of the first embodiment of the page management method of the present invention, and FIG. 5 is a diagram of the second and third embodiments of the page management method of the present invention. A conceptual diagram of the embodiment, FIG. 6 is a diagram showing the page management algorithm in the first embodiment, and FIG.
Figure 8 shows the page management algorithm in the second embodiment, Figure 8 shows the page management algorithm in the third embodiment, and Figure 9 shows the state transition diagram of the TLB specification field and TLB reference bit. show. 10... Page table, 11... Page table entry, 12... TLB storage field, 13.
...Cache storage amount field, 20...TLB specification field, 21...TLB reference bit, 32...
・Reference bit, 40... Processor, 41... TL
B device, 42...Memory device, 43...Disk device, 45a...Empty page, 45b...Unnecessary page, 4
5c...forced raid 6 days

Claims (1)

[Scope of Claims] 1. In a computer system in which a virtual space is configured by a memory device and a disk device, and has a page table indicating a correspondence between a logical page number and a physical page number of the virtual space, an entry of the page table is provided. A storage field is provided internally to indicate whether or not the control information and data of the corresponding page are stored in various storage devices of the computer system, and the storage field is stored only during the period when the control information and data of the page are stored. 1. A computer system characterized in that the storage field is used to determine a page to be transferred between a memory device and a disk device. 2. In a computer system in which a virtual space is configured by a memory device and a disk device, and has a page table that indicates the correspondence between a logical page number and a physical page number of the virtual space, a corresponding page is stored in an entry of the page table. A storage amount field indicating the amount of control information and data stored in various storage devices of the computer system is provided, and the storage amount field is updated according to the reading and discarding of page control information and data. A computer system characterized in that a page to be transferred between a device and a disk device is determined using the storage amount field. 3. A TLB device that configures a virtual space with a memory device and a disk device, has a page table showing the correspondence between the logical page number and physical page number of the virtual space, and stores a part of the page table. In a computer system equipped with at least one processor including the following, a TL indicating in which TLB device of which processor the entry is stored is stored inside the entry of the page table.
A computer system characterized in that a TLB specification field is provided, and pages to be transferred between a memory device and a disk device are determined using the TLB specification field. 4. A TLB device that configures a virtual space with a memory device and a disk device, has a page table showing the correspondence between the logical page number and physical page number of the virtual space, and stores a part of the page table. In a computer system equipped with at least one processor including a processor, a T indicating which processor's TLB device the entry is stored in is stored inside the entry of the page table.
A computer system characterized in that an LB reference bit is provided and a page to be transferred between a memory device and a disk device is determined using the TLB reference bit. 5. In the computer system of claim 3, the correspondence between logical page numbers and physical page numbers required by the processor does not exist in the TLB device, and the corresponding entry is read from the page table and stored in the TLB device. A computer characterized by having means for setting the TLB specification field in the entry of the page table to indicate that the TLB device that read the entry stores the contents of the entry when rewriting one entry. system. 6. In the computer system according to claim 3, the correspondence between logical page numbers and physical page numbers required by the processor does not exist in the TLB device, and the corresponding entry is read from the page table and stored in the TLB device. When rewriting one entry, set the TLB specification field in the entry of the page table to indicate that the TLB device that read it remembers the contents of the entry, and correspond to the page number before rewriting. A computer system comprising means for setting a TLB specification field of an entry in the page table to indicate that the TLB device that read the entry does not store the contents of the entry. 7. In the computer system according to claim 4, the correspondence between logical page numbers and physical page numbers required by the processor does not exist in the TLB device, and the corresponding entry is read from the page table and stored in the TLB device. A computer system comprising means for setting the TLB reference bit in an entry of the page table when rewriting one entry. 8. In the computer system according to claim 3, when writing back a page on a memory device to a disk device, check the TLB specification field in the entry corresponding to the page to be written back in the page table, and T.L.B.
The invention is characterized in that an invalidation request is issued only to the TLB device of the processor indicated by the specified field, and the TLB specified field is set to indicate that the TLB device of any processor does not store the corresponding entry. computer system. 9. In the computer system according to claim 4, when writing back a page on a memory device to a disk device, the page management means writes the TLB in the entry corresponding to the page to be written back in the page table. Check the reference bit, and if the TLB reference bit is set,
A computer system characterized by issuing an invalidation request to TLB devices of all processors and resetting the TLB reference bits. 10. A TLB device that configures a virtual space with a memory device and a disk device, has a page table showing the correspondence between the logical page number and physical page number of the virtual space, and stores a part of the page table. In a computer system equipped with at least one processor including The unnecessary pages that are not available are classified into strongly restricted pages whose page correspondence is stored in the TLB device and strongly restricted pages whose page correspondence is not stored in the TLB device, and the sum of the weakly restricted page and the empty page is calculated. is greater than or equal to the minimum limit value, only the weakly restricted page is written back to the disk device as an empty page, and if the sum of the weakly restricted page and the empty page is less than the minimum value,
The present invention further includes page management means for writing back all of the unnecessary pages to the disk device to make them empty pages, and reducing the number of invalidations of the TLB device by restricting writing back of the strongly restricted pages to the disk device. Featured computer system. 11. A TLB device that configures a virtual space with a memory device and a disk device, has a page table showing the correspondence between the logical page number and physical page number of the virtual space, and stores a part of the page table. In a computer system equipped with at least one processor including The pages are classified into strong restriction pages stored in the TLB device and weak restriction pages whose page correspondence is not stored in the TLB device. Until the number becomes 0, the weakly restricted pages are written back to the disk device in the order of unreferenced pages in descending order of time to become empty pages, and at this point, if the number of empty pages has not reached the minimum value. , page management means for writing back to the disk device in order of pages that have not been referenced for a longer time among the strongly restricted pages to make them empty pages until the number of empty pages reaches a minimum value; A computer system characterized in that the number of invalidations of a TLB device is reduced by limiting writing back of pages to a disk device. 12. A TLB device that configures a virtual space with a memory device and a disk device, has a page table showing the correspondence between the logical page number and physical page number of the virtual space, and stores a part of the page table. In a computer system equipped with at least one processor including The pages are classified into strong restriction pages stored in the TLB device and weak restriction pages whose page correspondence is not stored in the TLB device, and for each non-empty page on the memory device, if it is the weak restriction page, it is referenced. Indicates the number that is monotonically non-increasing for the time when the page is not referenced, and for the above-mentioned strong restriction page, sets a reference degree coefficient that indicates the value obtained by adding a constant value to the number that is monotonically non-increasing for the time that is not referenced. and page management means for writing back pages on the disk device to make them empty pages in order of decreasing reference degree coefficient among non-empty pages on the memory device until the number of empty pages reaches the minimum value. A computer system characterized in that the number of invalidations of a TLB device is reduced by restricting writing back of the strongly restricted page to a disk device.