JPS6034142B2 - Working set management method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a working set management method in a virtual memory type information processing system that operates with multiprogramming.

In a virtual memory type information processing system that operates with multiprogramming, the problem is how to allocate main memory pages to each program on the main memory. As a method for determining the number of main memory pages to be allocated to each program, the number of pages referenced by a certain program within a certain period of time (this is called the window size) is
A so-called working set method is known in which a set is reserved for the program.

(hereinafter referred to as the WS method). In order to accurately implement the WS method, each time a page in main memory is referenced, the referenced time is recorded as the last referenced time, and the window size is It is necessary to search for a page with a previous time recorded, remove it from the working set, and register it as a free page, making strict WS management impractical in terms of management overhead. , is actually realized as follows. That is, in order to manage how each page on the main memory is accessed, usage bits and usage counters corresponding to each page are prepared. The used bit is set when the corresponding page is accessed to the main memory. WS review management is started every time a certain WS review is triggered, checks the used bit for all pages on the main memory, and if this bit is on, that is, if there is a reference to the corresponding page, Usage counters are reset. When the usage bit is off, that is, when the corresponding page is not accessed, the usage count value is incremented. If the usage count value becomes larger than a certain value n, that is, if it is not referenced for n cycles and falls outside the window size, this page is removed from the working set frame to which it has been connected. As an unnecessary page,
Registered in the free page pool. If a page fault occurs during program execution, a page is taken from the free page pool and given to the program.

That is, it is connected to the working set frame corresponding to the program. With this method, the number of pages allocated to each program is reduced or expanded as necessary depending on the operating status of that program, so main memory is used more effectively than when pages are fixedly assigned to a program. Is possible.

By shortening the WS review cycle, it approaches the original working set management, and pages that have fallen outside the window size can be immediately identified and returned to the free page pool, improving main memory usage efficiency. I will do it.

On the other hand, if the WS review cycle is shortened, the overhead of the review process will increase, which will reduce the throughput of the information processing equipment, so it is an important issue to appropriately set the working set review cycle. Become. Also, depending on the program, it is better to review the working set at short intervals, and there are some programs where it is better to review the working set at short intervals, and there are other programs where it is better to review the working set at long intervals without reducing the main memory usage efficiency. By setting the review period, it is possible to reduce the overhead of reviewing the working set without reducing the usage efficiency of the main memory. On the other hand, the working set window size is not necessarily the same for each program, but it is possible to specify a window size suitable for each program, which improves the effective use of main memory and the throughput of information processing equipment. The effect is significant in terms of improvement. Conventionally, there was no means to control the cycle of reviewing the working set for each program, and a known method for controlling the window size was to set the maximum value of the usage count, but this method This is done until the unnecessary parts of the program are removed from the working set when the window size is increased.

This method has the disadvantage that the number of times the working set is reviewed increases, the overhead for this increases, and the effect of controlling the window size is reduced. The present invention makes it possible to specify the working set review period and the updating of the working set review for each working set frame, and to perform the working set review according to this designation. Accordingly, an appropriate window size can be specified for each working set frame, and an appropriate working set review cycle can also be set.

As a result, the overhead of reviewing the working set can be reduced, and the main memory usage efficiency can be increased. Therefore, the first object of the present invention is to realize a working set management method that uses main memory with high efficiency, and the second object is to reduce the management overhead in the working set management method.

Next, an embodiment of the present invention will be described. Prior to this, an outline of an implementation example of a conventional working set management method will be explained with reference to FIG.

The following tables are prepared to realize working set (hereinafter abbreviated as WS) management.

The WS frame control block (hereinafter abbreviated as WSCB) is a table for managing pages belonging to a WS frame, which is a unit of each WS management. Since it is assumed that the program is managed, each program has an entry i, and entry i belongs to that WS frame.

The number of pages PNi, the maximum number of pages allowed for the WS frame MXi, the first value MNi, and a pointer PTRi to the page list belonging to the WS frame are prepared. Pool frame control block 2 (hereinafter abbreviated as pool CB) is a table for managing unused pages that do not belong to any WS frame, and contains the number of unused pages PPN and the pointer PPTR to the unused page list. have.

The memory map 3 is a table for managing real pages on the main memory and has an entry for each page.

Each entry has a pointer section and a usage information section.
According to the pointer section, real pages constitute a page list belonging to any WS frame or pool frame.

As the usage information, usage bits UB and usage counts UC are prepared. The usage bit UB is set to "1", for example, when a page is referenced, and the usage count UC is updated when the WS is reviewed as shown later.

Further, a threshold value register 4 is prepared that holds the periodic threshold value (window size) to be removed from the WS. Further, a comparison circuit is provided for comparing the value of the limit value register 4 and the value of the usage count UC. WS that starts at regular intervals
The review timer interrupt causes the following operation to be performed for each WS frame.

That is, by sequentially tracing the memory map 3 using the pointer PTRi of WSCBI, the entry of the corresponding memory map is read out and the reference bit is checked. If this is "1", that is, if there is a reference, the reference bit is set to " 0
"At the same time, clear the usage count. If the reference bit is "0", count up the usage count. The result of this update and the value n of register 4
are compared by the comparison circuit 5, and if the value of the use count reaches n, this page is considered to be out of the working set, removed from the page list of this WS frame, and connected to the pool frame. (However, if the number of pages in that WS frame is already less than MNi, it will not be returned to the pool.) By performing this operation, the number of pages in the WS frame will be
Pages that are not referenced during the period will be removed from their WS frame and returned to the pool frame.

In the event of a page fault, first allocate a page from the pool frame to the WS frame of the program that generated this page fault, start transferring the requested page from the packing store, and check the number of pages in this WS frame. I do.

If the allocation results in a value greater than the maximum value MXi, if there is a page with a usage count of n in that WS frame, it is returned to the pool frame. If not, update the usage count while sequentially checking and clearing the usage bit for each page in this WS frame. As a result of this update, this process is performed until the usage count becomes n, and the page is used. Return pages whose count reaches n to the pool. As a result of allocation, the number of pages in the WS frame is greater than the minimum value,
If it is less than the maximum value, it is checked whether this WS frame has a usage count of n pages, and if there is, it is removed from the WS frame and returned to the pool frame. If there is no page with a usage count of n, the page is returned to the pool only if there is a shortage in the number of pages in the pool, that is, if the current number of pages in the pool is smaller than the shortage threshold value. W
If the number of pages PNi in the S frame is less than or equal to the minimum value MNi, the pages are not returned to the pool. Note that page allocation from the pool frame to the WS frame is performed as follows.

First, the page number PPN of the pool frame control block is decreased by 1, and the value of the pointer ratio PTR, that is, the page number of the beginning of the page at that time, is saved, and PP
Memory map 3 specified by TR (increase value i)
The value of the pointer part PTRi of entry i, that is, the number of the page connected next to the first page is pooled.
Set the outside point of the frame control block.

In other words, this is set as the new first page. This completes the removal process from the pool frame. Next, the value of the pointer PTRi of the i-th entry of the WSCB corresponding to the WS frame to which the page is to be connected is set to the pointer PTRi of the entry i corresponding to the pointer saved earlier in the memory map. Thereafter, the previously saved value j is set to the pointer PTRi, and the current page number PN is increased by one. This means that the page that was previously removed from the pool frame is connected to the WS frame. Pages are returned from the WS frame to the pool frame at the same time.

Next, the configuration of an embodiment of the present invention will be described.

FIG. 2 is a block diagram showing the configuration of an embodiment embodying the present invention. In this embodiment, WSCBI includes, in addition to the fields shown in FIG. 1, a valid bit V for indicating the validity of each field, and a corresponding W
In the S frame, there is a field P that holds the WS review cycle, a review cycle counter PC that is a field that holds the elapsed cycle since the previous WS review trigger, and a field UW that holds the status of updating the usage count when reviewing the working set. Motsu. The value of field PC in WSCBI is
A twill line is sent to the count up circuit 9, and its output is WSC
It is applied to field PC of BI and also to one input of comparator circuit 7.

The value of field P of WSCBI is applied to the other input of this comparison circuit 7. Further, the value of field UC of memory map 3 is applied to one input of adder circuit 8, the value of field UW of WSCBI is applied to the other input, and the output of this adder circuit 8 is applied to UC of memory map 3. The field is returned and connected to one input of the comparison circuit 5.

The other input of the comparison circuit 5 is applied with a threshold value for the usage count UC of the register 4. next,
The operation in this embodiment will be explained.

In this embodiment, a WS frame is prepared for each program, that is, a task, and the working set review cycle P and usage count update UW can be specified for each program by a job control statement.

At the start of a program, when a task control block i is given to this program, WSCBi is also allocated, the valid bit Vi of WSCBi is turned on, and the review period P specified in the job control statement and
The usage count updating UW is set in the corresponding field of WSCBi, and the review period counter U
Cj is cleared.

From now on, program loading, page loading at the time of page fault, etc. will be performed using the WS frame i specified in the task control block.
will be carried out against.

When reviewing the WS, which is activated at regular intervals, the WS frame selection control unit (not shown) sequentially selects the currently used WS frames whose valid bits Vi are on, and selects them. WSCBj review period counter P corresponding to the WS frame i
A count-up circuit 9 counts up the value of Ci, and a comparison circuit 7 compares this result with the value of Pi. When the comparison circuit 7 detects a match, that is, when the corresponding WS frame is in the review period, it clears the value of PCj and starts WS review for this WS frame. If the comparison circuit 7 does not detect a match, that is, for a WS frame whose corresponding WS frame is not in the review cycle, the S review is not performed, and it is checked whether the next WS frame is in the review cycle.

After performing the above processing for all WSs (M pieces), the WS,
The selection control unit sets an isotaval timer to trigger the next WS review, and ends the process. This situation is shown in Figure 3. The WS review control unit uses the specified W
Using PTRj for the S frame and the pointer PTRj of each entry in the memory map, the following processing is performed for each page while sequentially searching for pages belonging to the WS frame.

That is, the corresponding usage bit UBj is set, and if it is on, it is cleared and the usage count U is set.
Clear the value of Cj.

If the usage bit UCj is off, the usage count UC
UWi during UC update of WSCBj.
is added by the adder circuit 8, and this result is compared with the use count limit value of the dark value register 4 by the comparator circuit 5. If the result is greater than or equal to the threshold value, that is, if the corresponding page has not been accessed during the review period specified by the product of Pi and UWj, this page is removed from the WS. As such, it is removed from the corresponding WS slot and returned to the pool slot.

FIG. 3 shows the operation of the WS review control unit explained above.

One embodiment of the present invention has been described above, but in the above description, only the operations of the WS frame selection control unit and the WS review control unit will be described, and the explanation of the specific configuration will be complicated, and the gist of the present invention will not be explained. Although it is omitted because it is not directly related to the above, it is clear that it can be realized using firmware, software, or hardware. Also, in this embodiment, the WS frame is set for each program. Although it is said that it will be prepared, it is not necessary to do it this way and it is also possible to configure it so that one WS frame is allocated to multiple programs.Also, regarding the specific method of managing page usage status, etc. There are several possible ways to implement this.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional WS management method, FIG. 2 is a block diagram showing the configuration of an embodiment embodying the present invention, and FIG. 3 is a block diagram showing an embodiment of the present invention. A flowchart of processing of the review WS frame selection control unit in the embodiment is shown. FIG. 4 shows a flowchart of the processing of the WS review control unit in the embodiment of the present invention. 1 is a WS frame control block, 2 is a pool frame control block, 3 is a memory map, 4 is a dark value register, 5 is a comparison circuit, 6 is a count up circuit, 7 is a count up circuit, 8 indicates an additive circuit. Hair 1 figure Hair 3 figure Hair 2 figure Hair 4 figure

Claims (1)

[Claims] 1. In a virtual memory type information processing system that operates with multiple programs, the working set frame is the unit for managing working sets, and the frequency of working set reviews that should be performed in each working set frame since the previous working set review. means for retaining the elapsed cycle of the working set; and means for retaining the update range of the usage count indicating the usage status to be updated when reviewing the working set for the working set frame; to select each working set frame in turn, update the elapsed cycle in the selected working set frame, and compare the updated elapsed cycle with the review cycle to update the working set frame in the working set review cycle. a means for initiating a working set review only for those cases; and
When reviewing the activated working set by the means, the review cycle and window size in working set management can be controlled by having means for updating the usage count according to the specified update width. A working set management method characterized by: