Method and apparatus for reducing page replacement time in system using demand paging technique

Abstract

A method and apparatus for reducing a page replacement time in a system using a demand paging technique are provided. The apparatus includes a memory management unit which transmits a signal indicating that a page fault occurs, a device driver which reads a page having the page fault from a nonvolatile memory, and a page fault handler that searches and secures a space for storing the page having the page fault in a memory. The searching and securing of the space in the memory is performed within a limited time calculated beforehand and a part of data to be loaded to the memory of the system is stored in the nonvolatile memory.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and features of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:

FIG. 1 is a diagram showing a demand paging process according to the relationship between a software process and a device I/O as time passes;

FIG. 2 is a time chart showing a paging process while reducing a data loading time according to an exemplary embodiment of the invention;

FIG. 3 is a diagram showing the operation of a clock algorithm to which a process of reducing a page replacement time used according to the exemplary embodiment of the invention is applied;

FIG. 4 is a diagram showing the process of reducing a page replacement time in the clock algorithm shown in FIG. 3 according to the exemplary embodiment of the invention;

FIG. 5 is a diagram showing a process of selecting a replacement page in a Mach 2.5 algorithm;

FIG. 6 is a diagram showing a process of rearranging a movement point of an invalid list in the Mach 2.5 algorithm shown in FIG. 5 according to the exemplary embodiment of the invention;

FIG. 7 is a flowchart showing a process of transmitting a read command and performing paging in a memory according to the exemplary embodiment of the invention;

FIG. 8 is a flowchart showing a process of reducing a time required for performing demand paging according to the exemplary embodiment of the invention; and

FIG. 9 is a block diagram showing the construction of a system according the exemplary embodiment of the invention.

Claims

1. A method of reducing a page replacement time in a system using a demand paging technique, the method comprising: receiving a signal indicating that a page fault occurs;reading a page having the page fault from a nonvolatile memory; andsearching and securing a space to store the page having the page fault in a memory,wherein the searching and securing of the space in the memory is performed within a limited time calculated beforehand.

2. The method of claim 1, wherein the limited time is shorter than a time required for performing reading of the page having the page fault.

3. The method of claim 1, wherein the searching and securing of the space in the memory is performed before the system performs reading of the page having the page fault.

4. The method of claim 1, wherein the reading of the page having the page fault comprises: transmitting information of the page having the page fault to the nonvolatile memory; andreceiving data of the page having the page fault from the nonvolatile memory.

5. The method of claim 1, wherein the searching and securing of the space in the memory comprises: moving a pointer that manages a plurality of pages to be replaced, the moving of the pointer being performed within the limited time; andsecuring a page indicated by the moved pointer as a space for storing the page having the page fault.

6. The method of claim 5, wherein the limited time is shorter than a time required for performing the reading of the page having the page fault.

7. The method of claim 1, wherein: the system divides pages stored in the memory into a first group and a second group for memory management, the first group being a list of pages currently referenced and the second group being a list of pages to be replaced in the future;the searching and securing of the space in the memory comprises securing a space for storing the page in the second group.

8. The method of claim 7, wherein the searching and securing of the space in the memory further comprises exchanging a page from the first group to the second group within the limited time.

9. The method of claim 8, wherein the limited time is shorter than a time required for performing the reading of the page having the page fault.

10. An apparatus for reducing a page replacement time, the apparatus comprising: a nonvolatile storage device which stores data;a memory which receives and stores the data from the nonvolatile storage device and manages the data through demand paging, the memory configured to store data when power is supplied;a memory management unit which transmits a signal indicating that a page fault occurs in the memory;a page fault handler which extracts information of the page having the page fault and searches and secures a space configured to store the page having the page fault in the memory; anda device driver which transmits information of the page having the page fault to the nonvolatile storage device and receives data from the nonvolatile storage device,wherein the page fault handler extracts the information and searches and secures the space within a limited time calculated beforehand.

11. The apparatus of claim 10, wherein the limited time is shorter than a time from when the device driver receives the information of the page having the page fault in the memory until the data is received from the nonvolatile storage device.

12. The apparatus of claim 10 wherein the page fault handler searches and secures the space in the memory before the device driver receives the data from the nonvolatile storage device.

13. The apparatus of claim 10, wherein: the page fault handler moves a pointer that manages a plurality of pages to be replaced, and secures a page indicated by the moved pointer as a space for storing the page having the page fault; andthe pointer is moved within the limited time.

14. The apparatus of claim 13, wherein the limited time is shorter than a time from when the device driver receives the information of the page having the page fault in the memory until the data is received from the nonvolatile storage device.

15. The apparatus of claim 10, wherein: the page fault handler divides pages stored in the memory into a first group and a second group for memory management, the first group being a list of pages currently referenced and the second group being a list of pages to be replaced in the future;the searching and securing of the memory space comprises securing a space for storing the page in the second group.

16. The apparatus of claim 15, wherein a page to be exchanged or arranged between the first and second groups is moved within the limited time.

17. The apparatus of claim 16, wherein the limited time is shorter than a time from when the device driver receives the information of the page having the page fault in the memory until the data is received from the nonvolatile storage device.

18. The apparatus of claim 10, wherein the nonvolatile storage device comprises a flash memory and a buffer or a register that transmits data of the flash memory to the apparatus for reducing a page replacement time.

19. A method of reducing a page replacement time in a system using a page demand paging technique, the method comprising: receiving a signal indicating that a page fault occurs;reading a page having the page fault from a nonvolatile memory into a buffer; andsearching and securing a space to store the page having the page fault in a memory when the page having the page fault is read into the buffer.

20. The method of claim 19, wherein the searching and securing a space to store the page having the page fault is completed before the reading of the page having the page fault is completed.