JPH04111133A - Stack area control system - Google Patents

Abstract

PURPOSE:To improve the thread executing performance by preventing a page-out state of a virtual storage area to an external storage and at the same time invalidating the areas that are already paged out to the external storage. CONSTITUTION:When the end of a program is detected in a step S13, a fact whether the area used in the program is equal to a stack area of not is decided in a step S14. If not, a general area is opened in a step S15. If so, a control page table is checked to the stack area in a step S16. Then the changed bit of the used page are cleared in a step S17. Thus the data are evaporated out of a memory, and a fact whether the end conditions are satisfied or not is decided in a step S18. As a result, the undesired page-out and page-in states can be prevented.

Description

[Detailed Description of the Invention] [Summary] At the end of parallel processing executed by a plurality of program executables in the same space, a virtual storage area used as a stack for thread processing is transferred to an external storage device. Regarding a stack area control method that prevents page-outs and invalidates areas that have already been paged out to an external storage device, an external storage device for the virtual storage area that was used as a stack area at the end of program processing in a thread. The purpose was to improve thread execution performance by preventing page-outs to external storage devices and by invalidating areas that had already been paged out to external storage devices, and used the stack area as a work area. At the end of the program, check the change bit of the page table from the top page of the stack area in the direction of the lower address, clear the set change bit, and reach the page for which the change focus is not set or the lowest page. When the program is terminated, the processing is terminated, and the content of the stack area that was used at the time of termination of the program is discarded.

[Industrial application field]

The present invention relates to a stack area control method, and more specifically, the present invention relates to a method for controlling a stack area, and more specifically, the present invention relates to a method for controlling a stack area.
When the parallel processing executed by This paper relates to a stack area control method.

(Problems to be solved by conventional technology and inventions) In recent operating systems, one process (space)
With the demand for multiplexing of processing within a process, it has become necessary to generate a plurality of simple program execution bodies within a process. For this reason, a function is provided to generate a thread as a simple program execution body within a process.

This thread is activated when a message is received, and when the program processing corresponding to the received message is completed, it waits for the next message to be received. Each thread operates using a stack area as a program work area when performing program processing. In the conventional stack area control method, the stack area is saved in the state it was in use at the time the thread end finished processing, and is reused for the next process.

If the real memory allocated to the virtual storage area used as the stack area is robbed while the thread is waiting for the next process, the contents of the virtual storage area will be A pageout to an external storage device occurs. Furthermore, when a thread starts the next process and accesses an area that was previously paged out, that page is paged in from the external storage device.

As described above, even though the contents of the stack area used in connection with that process are completely unnecessary when a thread finishes program processing, page-out to the virtual storage area when real memory is stolen , and a page-in occurs in the next process of the thread, resulting in a problem in that the execution performance of the thread as a program execution body deteriorates.

The present invention prevents a virtual storage area used as a stack area from being paged out to an external storage device at the end of program processing in a thread, and invalidates an area that has already been paged out to an external storage device. The purpose of this is to improve thread execution performance.

[Means and operations for solving the problems] FIG. 1 is a functional block diagram of the present invention. This figure is a functional block diagram of a method for controlling the stack area at the end of processing of a program executable, such as a thread, that uses the stack area as a work area. In the present invention, the usage status of each page in the stack area is managed, for example, by the change focus setting status of the page table, and setting the change bit indicates that the contents of that page have been rewritten. do.

In FIG. 1, when the thread processing is completed, the change bits for each page of the page table are checked from the top page of the stack area toward the lower addresses at step 1, and the set change bits are canceled at step 2. For example, clearing is performed from 1 to O, and the process ends when a page with no change bit set at 3 or the lowest page of the stack area is reached.

That is, since pages of the stack area are sequentially used from the top to the lowest address, by checking the change bits from the top page, all the change bits that have already been set will be cleared. The state in which the change focus is cleared indicates that the page contents have never been rewritten as described above, and page out to the external storage device is prevented when real memory is stolen, and For example, the contents of the virtual memory that have been paged out are volatilized, and unnecessary page-in is also prevented when the next process is started in a thread or rad.

[Example] The second part is an example of the stack control routine according to the present invention. In the same figure, when the end of the program processing is detected in step (S) 10, the flow shifts to the Sll stack control routine.

In the stack control routine, the page table is inspected at ■ from the topmost page table entry in the stack downwards, the change focus is canceled, or cleared, at ■, and the processing termination condition is determined at ■. It will be done.

The process ends when the lowest page table entry is reached or when a page table entry for which the change bit is not set is reached. then 312
The state of the thread is set to wait for the next process.

FIG. 3 is a flow chart of an embodiment of the stack area control method. In the figure, when the end of a program is detected in step (S)13, it is determined in S14 whether the area used in the program is a stack area, and if it is not a stack area, the general area is released in S15. will be held.

On the other hand, if it is a stack area, the management page table is checked for the stack area in S16, and the memory data is evaporated by clearing the change bit of the page being used in 317. Rare, S
At step 18, it is determined whether the termination condition is satisfied.

If the table entry of the lowest page has not been reached and the page table entry in which the change bit is not set has not been reached when the termination condition is determined in step 318, the processing from step 316 is repeated. If the termination condition is satisfied, in S19, if no real memory is allocated to the stack area when the stack is reused, real memory with undefined content is allocated to the stack area.

FIG. 4 is an example of a page table and a stack area in a virtual storage area and a real storage area. Figure (a) shows a virtual storage area, including a page table 20 and a stack area 2.
1 is provided. In contrast, the real storage area is shown (
In b), only the used real storage area 23 of the page table 22 and stack area is shown.

FIG. 5 is an example of a method for discarding unnecessary virtual storage areas in the stack. FIG. 3(a) shows a method for managing the virtual memory usage state in the stack area, in which pages in the stack area 31 for the thread 30 that are used from the high address side are referenced in the page table 32. Both the bit and the change bit are 1. Here, the reference bit indicates that this page has been accessed, and the modified bit indicates that the contents of the page have been rewritten as described above. The state after rejection shown in FIG. 5(b) shows a state in which the changed focus for the used page in the page table 32 is all set to 0.

[Effects of the Invention] As explained above, according to the present invention, when program processing in a thread as a program execution body is completed, the contents of the stack used in connection with the processing are discarded, and unnecessary pages are Page-out and page-in are prevented, which greatly contributes to improving the execution performance of the program execution body.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram of the present invention. FIG. 2 is a diagram showing an embodiment of the stack control routine in the present invention. FIG. 3 is a flowchart of an embodiment of the stack area control method. FIG. 4 is a virtual diagram. FIG. 5 is a diagram showing an embodiment of a page table and a stack area in a storage area and a real storage area, and FIG. 20 22 32...Page table, 2131...
・Stack header, 30...threads.

Claims (1)

[Scope of Claims] 1) At the end of a program that uses a stack area as a work area, check the change bits of the page table from the top page of the stack area in the direction of lower addresses (1), and check if the change bits are set. The change bit that is currently in use is cleared (2), and the process ends when the page for which the change bit is not set or the lowest open page is reached (3). A stack area control method characterized in that the contents of the stack area are discarded. 2) The stack according to claim 1, wherein when the stack area is reused after the processing ends (3), when no real memory is set for the stack area, a real memory with undefined content is allocated to the stack area. Area control method. 3) The stack area control method according to claim 1, wherein the program using the stack area is started when a message is received, and transitions to a message reception waiting state when the processing ends (3).