JPH04149751A - Method for processing garbage collection - Google Patents

Abstract

PURPOSE:To execute garbage collection without damaging the real time processing of data processing by shortening the interruption time for data processing interrupted due to the execution of a garbage collection. CONSTITUTION:Differing from the garbage collection processing of copying system, an area reclamation part 14 is constructed so as to remain the identical data in the data development area 15 of a copy source during the garbage collection processing. An area management part 13 can obtain the data immediately without through a pointer 16 even when data development area 15 of the processing request destination is to be copied on the other memory area 10 to be divided according to the garbage collection when receiving the reference processing request of a data development area 15 to be issued from an instruction execution part 12 and the check processing request of the content comparison of two data development area 15. Therefore, the result value can be returned to an instruction execution part 12. Thus, the garbage collection processing can be executed without damaging the real time processing of data processing.

Description

[Detailed Description of the Invention] (Summary) A memory space is divided into two parts, and the data in the data development area in use, which is developed in one divided space, is continuously arranged and copied into the other divided space. By doing this, we aim to make it possible to reuse the data expansion area without impairing the real-time processing of data, regarding the garbage collection/action processing method that reuses the unused data expansion area. When copying to the other partitioned space, the reusing unit that reuses the memory space leaves the same data in the data expansion area of the copy source until all copies are completed. In addition, when rewriting data, the management unit that sets a pointer between the copy source and the copy destination and manages the memory space uses the data pointed to by the pointer of the data expansion area to expand the data. In addition to rewriting the expansion area, when checking the consistency of two data expansion areas, the configuration is such that the data expansion area pointed to by the pointer of the data expansion area is taken into consideration when performing the checking process. do.

[Industrial application field]

The present invention divides a memory space into two parts, and copies the data in the currently used data expansion area expanded into one divided space to the other divided space in a continuous manner. The present invention relates to a garbage collection processing method that reuses a data expansion area, and particularly relates to a garbage collection processing method that enables reuse processing of this data expansion area without impairing real-time data processing. It is something.

In languages such as L, l S P languages that acquire and manage data areas at runtime, memory areas that are no longer needed and are left in the 2 memory space are automatically reclaimed. Then, garbage collection will be performed to make it available for reuse. This Gar\,2 correction must be configured so that the original data processing can be executed without being hindered.

[Prior Art] Garbage collection can be roughly divided into two types: free list type and copy type.

This free list garbage collection is a method in which scattered free areas that can be reused are successively connected with pointers and managed as a free list. In other words, as shown in Figure 3, by sequentially following the usage pointers, the memory area in use is identified and a record indicating that it is in use is added, and then unnecessary memory areas with no record of being in use are identified. A free list is created by selecting areas and connecting these unnecessary memory areas with free pointers. Then, when a new memory area is required, it is configured to be allocated from this free list.

In this free list-based garbage collection, both the process of following usage pointers and the process of creating a free list can be performed little by little during normal data processing. Since the process of moving the memory area is not required, the data can be referenced even during garbage collection.

However, in the case of data rewriting, processing such as stack registration is required in order to avoid creating a pointer pointing to an unscanned memory area from an already scanned memory area, but reference processing Since the frequency of rewriting processing is low compared to , this processing is not a big burden.If you follow this free list method of garbage collection from now on, you will be able to perform garbage collection without impairing the real-time processing of 5 data processing. In addition to this, there is also the advantage that the overhead is small.In addition to this, there is also the advantage that it can be executed efficiently on a general-purpose machine.

However, free list garbage collection does not move the memory area, so the usable memory area is fragmented and connected to the free list, so it cannot handle large memory area acquisition requests. The problem is that it cannot be done.

In contrast, copy-only garbage collection
By dividing the memory space into two parts, and when the usage status of one memory division space reaches a predetermined state, the data in the memory area in use is continuously arranged and copied to the other memory division space. This is a method of reusing unused memory areas. That is, as shown in FIG. 4, the memory areas in use are sequentially selected by sequentially following the use pointers, and the memory areas in use are successively arranged and copied to the other memory partition space. A record indicating that it has been copied (copy mark record) is added to the area, and a pointer to the copy destination is set. After all copy processing is completed, the memory that was the copy source is The pointer to the divided space is disconnected, and when a new memory area is needed, the configuration is such that allocation is made from the continuous free memory area following this organized memory area in use. .

Unlike the free list method, this one-copy garbage collection has the advantage of being able to respond to requests for acquisition of large memory areas because the available memory areas are grouped together. and,
Since the copies are made in the order of pointers, linearity is also improved. It also has the advantage that it can be executed efficiently on a general-purpose machine.

However, there is a problem in that during garbage collection, a pointer dedicated to the garbage collection is set, so normal data processing cannot be performed. That is, when garbage collection is executed, it cannot be performed without interrupting the original data processing, and there has been a problem that it cannot be implemented in a data processing device that requires real-time processing.

In order to eliminate the disadvantages of such copy-only garbage collection, when following a pointer during normal data processing, if a copy mark recorded during garbage collection is detected, the There is also a conventional technique that also traces a pointer held by a memory area to which a copy mark is attached. In this way, copy-only garbage collection can be performed little by little, and garbage collection can be performed with a short interruption of normal data processing.

[tlff to be solved by the invention] However, if a method is adopted in which the pointer is followed by taking into account the copy mark recorded during garbage collection, each time the pointer is referenced, the copy recorded by the garbage collection process is This means that it is necessary to perform a process of checking whether or not a mark is recorded, and then, according to the result of the check, a process of following the pointer. The problem remains that real-time processing is impaired by significantly degrading the performance of the original data processing.

In order to deal with this, it is conceivable to provide a transparent pointer hardware mechanism implemented in a hard disk control device or the like. If this transparent pointer hardware mechanism is provided, when the effective address is determined, when the copy source memory area is referenced, it will be possible to automatically switch to the copy destination memory area, so the pointer will not be traced twice. This can prevent performance deterioration due to However, in order to implement such a transparent pointer, a special hardware mechanism must be provided, which creates a new problem that it cannot be implemented on a general-purpose machine.

The present invention has been made in view of the above circumstances, and consists of dividing the memory space into two parts, and continuously transferring the data in the data expansion area in use that is expanded to one divided space to the other divided space. Garbage collection processing is performed without compromising real-time data processing in a copy-one garbage collection processing method that reuses unused data development areas by copying them side by side. The purpose is to provide a new garbage collection processing method that makes it possible to

[Means to solve the problem]

FIG. 1 is a diagram showing the principle configuration of the present invention.

In the figure, 1 is a data processing device equipped with the present invention. This data processing device 1 includes a memory area 10, a program development section 11, an instruction execution section 12, an area management section 13, and an area reuse section 14.

This memory area 10 develops a data development area 15 for storing data to be processed, a program development section 11 develops an application engine program that exhibits a predetermined data processing function, and an instruction execution section 12, Program development part 1
The area management unit 13 executes management processing of the memory area 10, and the g area reuse unit 14 decodes and executes the expanded program description of the memory area 10, for example. Sometimes, a copy-only garbage collection process is executed to reuse the memory area IO.

The instruction execution unit 12 provides the area management unit 13 with reference processing for the data expansion area 15, processing for creating the data expansion area 15, processing for rewriting the data expansion area 15, and comparison of the contents of two data expansion areas 15. , and the matching of the two data development areas 15 is requested.

The area management unit 13 executes the processing requested by the instruction execution unit 12 and responds to the instruction execution unit 12 with the result value.

The area reusing unit 14 divides the memory area 10 into two and copies the data in the currently used data expansion area 15 that is expanded in one memory area 10 to the other memory area 10 in a continuous manner. By doing so, the unused data expansion area 15
Execute reuse.

In executing this process, the area reusing unit 14 processes so that the same data remains in the data expansion area 15 of the copy source until all copying processes to the other memory area 10 are completed, and A pointer 16 is set between the data development area 15 of the copy source and the data development area 15 of the copy destination. Preferably, the pointers 16 are mutual pointers that point to the data development area 15 of the other party without having a master-slave relationship.

In this way, the area reusing unit 14 uses the other memory area 1
Since the same data is left in the data expansion area 15 of the copy source until all copy processing to 0 is completed, the area management unit 13 is configured to keep the same data in the area reuse unit 14 during processing. Therefore, the area reuse unit 14 can execute memory area reorganization processing little by little in parallel with the processing of the instruction execution unit 12.

C Effect] In the present invention, unlike the conventional copy-one-type garbage collection processing, the 7 area reuse unit 14 also stores the same data in the data development area 15 of the copy source during the garbage collection processing. Configure it to remain.

Since it is configured in this way, the area management unit 13 is configured to handle the data expansion area 1 issued from the instruction execution unit 12.
When receiving a request for reference processing in 5 or a request for inspection processing to compare the contents of two pig expansion areas 15, the data expansion area 15 that is the processing request destination is divided into the other one along the middle of the garbage collection area 5. Even if the data is copied to the memory area 10, it is possible to immediately return the result value to the instruction execution unit 12 in response to the issued processing request without following the pointer (the data can be obtained immediately). become able to.

On the other hand, when the area management unit 13 receives a request for rewriting the data expansion area 15 issued from the instruction execution unit 12, the area management unit 13 determines that the copy source data expansion area 15 and the copy destination data expansion area 15 have the same data. Consistent with the management configuration, if the data development area 15 for which a rewriting request is requested has a pointer 16, the pointer 16 is
Processing is performed so that the data development area 15 pointed to by is also rewritten to the same data.

Furthermore, when the area management unit 13 receives a request for checking the consistency of the two data expansion areas 15 issued from the instruction execution unit 12, the area management unit 13 performs a check on the data expansion area 15 of the copy source and the data expansion area 15 of the copy destination. In response to the fact that the two data development areas 15 that are requested to be inspected are configured to manage the same data, it is first determined whether or not the two data expansion areas 15 that are requested to be inspected are the same data expansion area 15. When it is determined through the process that they are not the same data expansion area 15, the data expansion area 15 pointed to by the pointer 16 is also cyanide, and the two data expansion areas 15 for which inspection is requested are the same data expansion area 15. We will decide whether or not.

For example, if the pointer 16 adopts a configuration in which the two data expansion areas 15 are managed in a master-slave relationship of a copy destination *S and a copy source area, the data expansion area to be inspected [15
is the copy source area, find the copy destination area, and check whether the two data development areas 15 of the copy destination area are the same data development area 15 or not. It is determined whether the data development areas 15 are the same data development area 15 or not. At this time, if the pointer 16 is configured with mutual pointers without a master-slave relationship,
The data expansion area 15 pointed to by the mutual pointer is specified for only one of the two data expansion areas 15 for which an inspection request is made, and this specified data expansion area 15 and the remaining data expansion area 15 for which an inspection request is made are identified. Since the consistency checking process can be executed by executing the sameness checking process, it is possible to eliminate the overhead based on the normalization process for the copy destination area.

As described above, according to the present invention, even if the area reusing unit 14 is in the middle of garbage collection, the area managing unit 1
3 is because it is possible to execute processing requests from the instruction execution unit 12 and to read data immediately without executing pointer tracking processing in response to the most frequently requested data reference processing request. This means that the deterioration of the original data processing performance can be minimized.

[Example] Hereinafter, the present invention will be explained in detail according to examples.

FIG. 2 illustrates an embodiment of the copy-only garbage collector according to the present invention executed by the area reusing unit 14 described in FIG. 1. In this figure, the left part shows the state of the memory space during the garbage collection process, and the right part shows the state of the memory space after the garbage collection process is completed. Here, in the left part, in order to prevent the pointer lines from becoming complicated, the two divided memory spaces are illustrated separated for convenience.

As shown in this figure, in the present invention, when copying from the old space (divided memory space on the left) to the new space (divided memory space on the right) according to the execution of garbage collection, the area reuse unit No. 14 is characterized in that processing is performed so that the same data remains in the copy source area of the old space until the copy processing for all areas is completed.

Then, the area reuse unit 14 creates a mutual pointer 20 (thick line pointer in the figure) between the two copy source areas and the copy destination area that points to the other's area without having a master-slave relationship. It is characterized by being processed as if it were held. This mutual pointer 20 is not used in areas that are not copied even during garbage collection processing, and is not used outside of garbage collection processing, so such Sometimes, as shown in the figure, it is set to point to its own area itself.

Since this configuration is adopted, the area management unit 13 explained in FIG. However, you will be able to immediately obtain the data you need to refer to. For example, in the diagram in the middle of processing in Figure 2, "C" can be obtained from "A" in the divided memory space on the right, and "C" can also be obtained from "A" in the divided memory space on the left. Thus, whether you follow the pointer pointing to the copy source area or the pointer pointing to the copy destination area, you can obtain the same data that is originally required.

On the other hand, in conjunction with adopting this configuration, the area management section 13
When rewriting an area, the copy destination area is also rewritten when the copy source area is rewritten, and the copy source area is also rewritten when the copy destination area is rewritten. Also, similar to free list garbage collection, in order to avoid creating pointers between old characters from scanned areas, the area to be pointed to is copied to a new space and a pointer to it is stored. I'm going to go there.

In addition to adopting this configuration, the area management section 1
3, when performing the matching process of the area itself, the comparison process is performed not only by comparing the pointers to be tested, but also by taking mutual pointers 20 into consideration.

Next, using the LISP language processing system as an example, the area management section 1
3 and the processing executed by the area reuse unit 14 will be explained.

When the area management unit 13 receives the issuance of ``rconS'' which is a new area acquisition process request from the instruction execution unit 12 explained in FIG. The garbage collection continuation process described in 6) is performed.

(1, 2) Garbage collection is not in progress, but if there is no free space in the current space, garbage collection startup processing is performed as described in (5) below.

(1, 3) Allocate the requested area in the current space.

Garbage collection executes the process of
As will be described later, the processing of the area management unit 13 will be interrupted when the interruption time reaches the specified value, so (1, 1)
When the specified interruption time is reached from the time point of processing (1, 2), execution of processing (1, 3) begins. In this way, garbage collection is executed little by little for each new area acquisition request.

The area management unit 13 receives from the instruction execution unit 12 a request for reference processing of the area pointed to by the designated pointer r(ar'''r
edr", (2, 1) refers to the CAR section/CDR section of the area to which the reference request is made and returns it to the instruction execution unit 12.

Execute the process. As mentioned above, in the present invention,
Since the configuration is such that data is left even in the copy source area during garbage collection, even if the reference request destination area is between old characters, the desired data can be retrieved immediately without following the pointer further. You can refer to it.

When the area management unit 13 receives from the instruction execution unit 12 the issuance of ``rrplaca'' and ``rrplacd'', which are requests to rewrite the area contents of the area at the root of the specified pointer, (3, 1) Garbage collection is not in progress. If so, the area with the rewrite request is rewritten with new content.

(3, 2) If garbage collection is in progress, perform the following processing.

(3, 2, 1) When the area for which the rewrite request is requested is a scanned area in the new space and the specified pointer points to an area in the old space, the area between the old characters is copied and the specified Change the pointer to point within the new space. The copying process at this time is executed according to the process (7) described later. 6 (3, 2, 2) The area in which the rewrite request is requested is rewritten with new content.

(3°2.3)? Follow the pointer of the other person and rewrite the other area with new content.

Execute the process.

The area management unit 13, from the instruction execution unit 12,
Upon receiving the issuance of 'eQJ, which is a processing request for checking the consistency of the areas pointed to by two pointers, (4, 1) compares the areas pointed to by the two specified pointers, and if they point to the same area, the result is true. It is returned to the instruction execution unit 12.

(4, 2) When determining in (4, 1) that they do not point to the same area, compare whether the mutual pointer 20 of one of the areas points to the other area, If they point to the same area, it is determined to be true and is returned to the instruction execution unit 12.

(4, 3) Otherwise, it is determined to be false and returned to the instruction execution unit 12.

Execute the process. As explained in the [Operation] column, since the copy source and copy destination areas are pointed by the mutual pointer 20 with no master-slave relationship, the area management unit I3
This makes it possible to execute the consistency check process for the N area itself with little overhead.

When the area reuse unit 14 receives a garbage collection startup processing request from the area management unit 13, it sets (5, 1) the current space as the old space and sets another space as the current space.

(5, 2) Initialize scanned area to none.

(5, 3) Copy processing is performed on the area pointed to by the root (pointing to the most root area).The copy processing at this time is as follows:
This is executed according to the process (7) described later.

(5,4) Set the status to “Copying 1 cent.

(5, 5) Continue garbage collection processing.

The continuation process at this time is executed according to the process (6) described later.

Execute the process.

When the area reusing unit 14 receives a request to continue overtime for garbage collection, (6) performs the following process as many times as necessary until the processing interruption time of the INJI area management unit 13 falls within the allowable range.

(6, 2) If the status is "copying", select one unscanned area and perform the next process.

(6, 2, 1) The area pointed from the unscanned castle is copied and updated to point to a new area. The copying process at this time is executed according to the process (7) described later.

(6, 2, 2) The unscanned area is set as the scanned area.

(6, 2, 3) When there are no more unscanned areas, the status is set to "cleaning up" and the entire area becomes an unscanned area.

(6, 3) If the status is “Cleaning up 2”, the unscanned area is
Select one and perform the next process.

(6, 3, 1) Change the mutual pointer 20 pointing to the multi-zero partner to point to itself.

(6, 3, 2) This area is defined as a scanned area.

(6, 3, 3) When there are no more unscanned areas, garbage collection ends.

Execute the process.

When the area reuse unit 14 receives a copy processing request, (7, 1) (7, 2) If the area with the copy request is in the new space, it does nothing,
Returns a pointer to the area as is.

If the area requested to be copied is in the old intersection, but already has a copy partner, a pointer to the copy partner is returned.

(7, 3) In other cases, perform the following processing.

(7, 3, 1) Allocate an area in the new space and copy the contents from the area. At this time, the contents are left as they are in the copy source area of the old relationship.

(7, 3, 2) The area of the new space is an unscanned area.

(7, 3, 3) A mutual pointer 20 is set with the copying partner.

(7, 3, 4) Returns a pointer to the new area.

Execute the process.

〔Effect of the invention〕

As explained above, according to the present invention, when a copy-based garbage collection processing method is implemented, the interruption time of data processing that is interrupted for garbage collection execution can be made extremely short. . Now, garbage collection can be performed without compromising real-time data processing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of the present invention, FIG. 2 is a practical example of the present invention, FIG. 3 is an explanatory diagram of free list type garbage collection, and FIG. 4 is an explanatory diagram of copy one type garbage collection. 1 is a data processing device, 10 is a memory area, 11 is a program expansion unit, 12 is an instruction execution unit, 13 is an area management unit, 14 is an area reuse unit, 15 is a data expansion area, 16 is a pointer, 20 is a mutual pointer.

Claims (2)

[Claims] (1) An area management unit (13) that manages a memory space, and an area reuse unit (14) that reorganizes the memory space, and the area reuse unit (14) divides the memory space into two. The unused data expansion area can be reused by dividing the data in the currently used data expansion area and expanding it into one divided space, and then sequentially arranging and copying the data in the other divided space. In the data processing device configured as follows, when copying data to the other divided space, the area reusing unit (14) stores data from the copy source until all copy processing to the divided space is completed. The same data is left in the data development area of the copy source, and a pointer (16) is set between the data development area of the copy source and the data development area of the copy destination, and the area management unit (13) When rewriting data, the data expansion area pointed to by the pointer (16) of the data expansion area that expands the data is also rewritten according to the same data, and the consistency of the two data expansion areas is checked. Garbage collection processing characterized in that when performing the processing, a consistency check process is executed in consideration of the data development area pointed to by the pointer (16) of the data development area. method. (2) In the garbage collection processing method according to claim (1), the pointers (16) set between the data expansion area of the copy source and the data expansion area of the copy destination are mutually connected without having a master-slave relationship. The area management unit (13) is configured with a mutual pointer that points to the other party's data expansion area, and when performing a consistency check process between two data expansion areas, the area management unit (13) When it is determined that the two data expansion areas are not the same data expansion area, the above mutual pointer of either data expansion area is specified, and the data expansion area pointed to by the specified mutual pointer and the remaining data expansion area for which inspection is requested are performed. The present invention is characterized in that it is configured to execute a process of determining the consistency of two data expansion areas for which inspection is requested by checking whether or not the two data expansion areas are the same data expansion area. garbage collection processing method.