Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Reexamination Certificate
1998-11-03
2001-03-13
Yoo, Do Hyun (Department: 2759)
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
C711S147000, C711S170000, C711S202000, C711S203000
Reexamination Certificate
active
06202134
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a paging processing system in a virtual storage device enabling prevention of reduction in throughput of a computer by reducing a time required for paging to be conducted in large-scale calculation and a paging processing method thereof.
2. Description of the Related Art
In a conventional computer having a virtual storage device, it is possible to virtually assume and use memory space larger than a physical memory mounted on the computer. The mechanism is compressing useless memory space by allocating only the memory space being actually used out of virtual memory space to memory space of the physical memory.
Allocation from virtual memory space to memory space of a physical memory is conducted on the basis of a page which is a small unit obtained by dividing each memory space. In other words, out of virtual pages, a page being actually used is allocated to a physical page.
In this system, however, a physical memory might run out of pages when numbers of programs are executed simultaneously or when a program requiring enormous memory space is run.
Therefore, so-called page-out processing is conducted which is to once write a page that has not been used for the longest time at a certain point of time to an external storage device to free a page of a physical memory and allocate the page to a page that is to be used at the current time point to carry out execution.
Thereafter, when there arises a need of reference/modification of data of the paged out page, so-called page-in processing is conducted which is to read, if a free physical page exists, the page data retained in the external storage device into the physical page and re-allocate the physical page to a virtual page. If there exists no free physical page, another page is once paged out to make a free page in the physical memory and conduct page-in processing.
Conventional virtual storage control device is disclosed, for example, in Japanese Patent Laying-open (Kokai) No. Showa 57-24081. Proposed in the virtual storage control device recited in Japanese Patent Laying-Open No. 57-24081 is a technique of conducting data page-in/page-out from/to an external storage device as mentioned above.
In large-scale numerical computation processing or simultaneous running of numbers of programs, a virtual storage device needs more pages than those of a mounted physical memory to require page-in/page-out processing to be conducted frequently. Numerical simulation such as the finite element method, for example, requires an enormous array area to cause a shortage of a storage region, so that paging to an external storage device occurs frequently.
With conventional techniques, however, page-in/page-out processing consumes so much time that occurrence of many times of paging processing will considerably reduce throughput of the entire computer.
The reason is as follows. In conventional techniques, when a real storage region fails to accommodate a virtual storage region, part of data in the real storage region is temporarily saved in an external storage device to make a free area and the virtual storage region is allocated to the free area, and the data saved in the external storage device is returned to the real storage region as required. Although a magnetic disk or a magnetic drum device is used as the external storage device responsible for the data writing/reading, a rate of data writing/reading to/from these storage devices is extremely low as compared with a rate of data writing/reading to/from a memory and much time will be accordingly consumed for paging processing.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a paging processing system in a virtual storage device which enables, in every computer having a virtual storage system connected over a network or connected directly, reduction in computer throughput to be prevented by reducing a time required for paging to be conducted for large-scale calculation which will cause a shortage of physical memory, and a paging processing method thereof.
Another object of the present invention is to provide a paging processing system in a virtual storage device enabling effective use of free memory resources in all the computers connected over a network etc. and a paging processing method thereof.
According to one aspect of the invention, a paging processing system in a virtual storage device of a computer system composed of a plurality of computers connected directly or over a network, comprises
page data reception checking means for notifying other computer which conducts page-out processing of the number of free physical pages of a physical memory in its own computer,
page data reception/transmission means for conducting processing of receiving page data from other computer and processing of returning received data,
page data transmission checking means for checking a state of vacancy of a physical memory of other computer based on the number of free physical pages notified by the page data reception checking means to select a computer as a page data transmission destination,
page data transmission/reception means for conducting transmission processing of transmitting page data of a virtual page to be paged out to the other computer selected and reception processing when transmitted page data is returned, and
page management means for controlling each of the means to manage a correspondence relationship between a virtual page and a physical page.
In the preferred construction, the page data transmission checking means inquires of other computer about the number of free physical pages for paging out a physical page in its own computer, and the page data reception checking means notifies other computer which conducts page-out processing of the number of free physical pages of a physical memory in its own computer according to the inquiry.
In another preferred construction, the page data reception checking means notifies every other computer of the number of free physical pages of a physical memory in its own computer every fixed time period.
In another preferred construction, the page data transmission checking means compares states of vacancy of physical memories in other computers based on the numbers of free physical pages notified by the page data reception checking means to select one of the other computers having the largest number of free physical pages as a page data transmission destination computer.
In another preferred construction, the page data transmission checking means inquires of other computer about the number of free physical pages for paging out a physical page in its own computer, the page data reception checking means notifies other computer which conducts page-out processing of the number of free physical pages of a physical memory in its own computer according to the inquiry, and the page data transmission checking means compares states of vacancy of physical memories in other computers based on the numbers of free physical pages notified by the page data reception checking means to select one of the other computers having the largest number of free physical pages as a page data transmission destination computer.
In another preferred construction, the page data reception checking means notifies every other computer of the number of free physical pages of a physical memory in its own computer every fixed time period, and the page data transmission checking means compares states of vacancy of physical memories in other computers based on the numbers of free physical pages notified by the page data reception checking means to select one of the other computers having the largest number of free physical pages as a page data transmission destination computer.
In another preferred construction, the page data reception checking means, when notifying other computer which conducts page-out processing of the number of free physical pages of a physical memory in its own computer, notifies that no free physical page exists if the number of free physical pages is not mo
Namazi Mehdi
NEC Corporation
Yoo Do Hyun
Young & Thompson
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