JP2007213252A - Garbage collection processing program and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent system failure or system performance deterioration as much as possible by executing the garbage collection of the old generation area in exact timing for the young generation region in a memory. <P>SOLUTION: A computer 10 executing the garbage collection processing program is provided with: a garbage collection execution part 21 for executing the garbage collection of the young generations and the garbage collection of the old generations for transferring all active objects of a young generation area 42 to an old generation area 43; a predicted quantity calculation part 24 for predicting quantity ES of the active objects of the young generation area 42; a memory monitoring part 22 for measuring free space OF of the old generation area 43; and a garbage collection control part 23 for comparing the predicted active object quantity ES of the young generation area 42 with the measured free space OF of the old generation area 43, and for making a garbage collection execution part 21 execute the garbage collection of the young generation area 42 when the free space OF is large, and for making a garbage collection execution part 21 execute the garbage collection of the old generation area 43, and then execute the garbage collection of the young generation area 42 when the free space OF is small. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a garbage collection processing program and a garbage collection processing method for dividing a heap area of a memory into a plurality of generation areas and collecting the garbage of each generation area.

  The garbage collection process (Garbage Collection) is a process for collecting unused objects in the memory area, more precisely, objects that are inaccessible from the system as garbage, and securing a free area in the memory area. In the present application, an object is a data structure assigned to a continuous area on a memory, such as a structure, a record type, or a Lisp cons cell. This garbage collection processing is executed to automatically manage the memory area that is dynamically used without being bound by the scope of the program. A dynamically used memory area is a memory area in which the lifetime of the memory area is different from the lifetime of the program. Such dynamic memory is allocated to the stack area and the heap area. The memory area whose lifetime is determined by the program scope is normally allocated to the stack area. A memory area whose lifetime is determined regardless of the program scope is allocated to the heap area.

  This heap area is often divided into a plurality of generational areas. An old generation area is an area that has a relatively long time since an object is allocated to a young generation area. The created object is first allocated to the youngest generation area by object allocation processing. In the allocation process, the garbage collection process is called when there is not enough free space in the young generation area. In the garbage collection process, among the objects belonging to the young generation area, the objects accessible from the system, that is, the surviving objects are moved to the old generation area. This is generally referred to as “inducting the Hall of Fame”. As a result of this garbage collection process, only unnecessary objects remain in the young generation area, and new objects are allocated to the young generation area. When objects that survive the garbage collection process are transferred from the young generation area, the free area of the old generation area gradually decreases. For this reason, in the prior art, when the user predetermines the conditions for which it is possible to secure a sufficient space for the old generation area, and when the conditions set by the user are satisfied, the garbage collection processing for the old generation area is performed. Executed.

  Non-patent literatures 1 and 2 below describe in detail the collection of garbage by generation and the basic method of collecting garbage.

"Basics of Garbage Collection and Recent Trends", Journal of Information Processing Society of Japan, Vol. 35, 1994, p.991-1032 `` Garbage Collection: Algorithms for Automatic Dynamic Memory Management '', Richard Jones, Rafael Lins, 1999, John Wiley & Sons Ltd. (ISBN 0-471-94148-4)

  However, in the prior art, as described above, the garbage collection processing of the old generation area is executed when the conditions determined by the user are satisfied, and thus there are the following problems. In other words, if this condition is set so that the user does not perform much garbage collection processing for the old generation area, the empty area of the old generation area is actually not sufficiently secured, In some cases, this condition may not be satisfied, and even if an attempt is made to collect garbage in a young generation area, the collection of garbage in the young generation area cannot be executed, which may cause a system failure. Conversely, if this condition is set so that the user frequently performs garbage collection processing for the old generation area, the old generation area is actually sufficiently reserved. Nevertheless, this condition is satisfied, and there is a problem that garbage collection in the old generation area is frequently executed, resulting in a decrease in system performance.

  Therefore, the present invention pays attention to the problems of the conventional technology as described above, and performs collection of garbage in the old generation area at an appropriate timing with respect to collection of garbage in the young generation area, thereby reducing system failure and system performance degradation. An object of the present invention is to provide a garbage collection processing program and a garbage collection processing method that can be avoided as much as possible.

A garbage collection processing program for achieving the above object is as follows:
In the garbage collection processing program that divides the memory heap area into multiple generation areas and collects garbage in each generation area,
Garbage collection execution step for collecting garbage from multiple generation areas,
By performing garbage collection for one generation area (hereinafter referred to as a young generation area) of a plurality of generation areas, a living object is selected from one or more objects existing in the young generation area. A movement amount prediction step for predicting the amount of an object to be moved to a generation area one older than a young generation area (hereinafter referred to as an old generation area) from past garbage collection results;
A free capacity measuring step for measuring the free capacity of the old generation area;
If the movement amount of the object in the young generation area predicted in the movement amount prediction step is smaller than the free space in the old generation area measured in the free capacity measurement step, the garbage collection in the young generation area is collected. If the movement amount of the object in the young generation area is greater than or equal to the free capacity of the old generation area, the garbage collection causes the area including the old generation area to be collected in the garbage collection execution step. Control steps;
Is executed by a computer having the memory.

Here, the garbage collection processing program is:
When it is measured during the collection of garbage in the young generation area that the free capacity of the old generation area is not sufficient for collecting garbage in the young generation area, the garbage collection control is performed. In the step, it is preferable that the garbage collection execution step interrupts or cancels the garbage collection of the young generation area and causes the area including the old generation area to collect garbage.

In addition, a garbage collection processing method for achieving the above-mentioned object is as follows:
In the garbage collection processing method that divides the memory heap area into multiple generation areas and collects garbage in each generation area,
Garbage collection execution process to collect trash from multiple generation areas,
By performing garbage collection for one generation area (hereinafter referred to as a young generation area) of a plurality of generation areas, a living object is selected from one or more objects existing in the young generation area. A movement amount prediction step for predicting the amount of objects to be moved to a generation area one older than the young generation area (hereinafter referred to as an old generation area) from past garbage collection results;
A free capacity measuring step of measuring the free capacity of the old generation area;
If the movement amount of the object in the young generation area predicted in the movement amount prediction step is smaller than the free space in the old generation area measured in the free space grasping step, the garbage collection in the young generation region is collected. If the amount of movement of the object in the young generation area is greater than or equal to the free capacity of the old generation area, the garbage collection causes the area including the old generation area to be collected in the garbage collection execution process. Control process;
It is characterized by including.

  According to the present invention, the amount of objects to be moved to the old generation area from one or more objects stored in the young generation area is predicted from the past garbage collection results, and this movement amount and the free space of the old generation area Compared with the above, garbage collection of the old generation area is executed according to the result, so the timing of garbage collection of the old generation area becomes relatively accurate, reducing the possibility of system failure and reducing system performance Can be suppressed.

  Hereinafter, various embodiments of dust collection processing according to the present invention will be described with reference to the drawings.

[First embodiment]
A first embodiment will be described with reference to FIGS.

  As shown in FIG. 1, the computer 10 that executes the garbage collection processing program 32 of the present embodiment includes a processor 11 that executes various processes, a program memory 30 that stores programs executed by the processor 11, and various data. Is stored in the data memory 40. Although not shown in FIG. 1, the computer 10 is a display for displaying processing results, an input device for inputting data and instructions, an external storage device, and another computer via an external communication network. And a communication processing device for communicating with the device.

  The computer 10 of this embodiment executes a program described in a Java language (Java is a trademark or registered trademark in the US Sun Microsystems, Inc. and other countries). For this reason, the computer 10 forms a virtual machine 12 in order to execute a program written in the Java language. A virtual machine program 31 for forming the virtual machine 12 in the computer 10 is stored in the program memory 30. The virtual machine program 31 includes a garbage collection process (Garbage Collection) program 32. The program memory 30 also stores an execution program 33 that is executed by the virtual machine 12. The execution program 33 is stored in the program memory 33 in a state converted from the Java language to an intermediate language.

  The heap area 41 of the data memory 40 is divided into a young generation area 42 and an old generation area 43.

  As described above, the processor 11 forms the virtual machine 12 by executing the virtual machine program 31. The virtual machine 12 functionally includes an instruction decoding unit 13 that decodes the execution program 33, an instruction execution unit 14 that executes an instruction decoded by the instruction decoding unit 13, and an instruction execution process in the instruction execution unit 14. It has a storage allocation unit 15 that manages and executes storage allocation to the data memory 40 when it becomes necessary to store objects, and a garbage collection processing unit 20 that collects unnecessary objects in the data memory 40. . The function of the dust collection processing unit 20 is realized by executing the dust collection processing program 32 described above.

  The garbage collection processing unit 20 is configured to collect the garbage collection execution unit 21 that collects each of the young generation area 42 and the old generation area 43 of the data memory 40, and the usage amount and free space of each area 42, 43. The memory monitoring unit 22 to measure, the predicted survival amount calculation unit 24 that predicts the object survival amount ES of the young generation area 42 based on the measurement result in the memory monitoring unit 22, and the respective units 21, 22, and 24 are controlled. And a dust collection control unit 23. The predicted survival amount calculation unit 24 measures a survival rate SR (= S / YU) which is a ratio of the survival amount S of the object after collecting the dust to the area usage amount YU of the object before collecting the dust, and the past survival rate SR. The survival rate prediction unit 25 that predicts the current survival rate ESR from the actual results, the current survival rate ESR of the predicted young generation region 42, and the current usage amount YU of the young generation region 42, A survival amount predicting unit 26 that predicts the survival amount ES (= YU · ESR) of the object.

  When the memory allocation unit 15 receives an object memory allocation command from the instruction execution unit 14, the storage allocation unit 15 secures a storage area in the young generation area 42 and returns the top address of this storage area to the instruction execution unit 14. If the storage allocation unit 15 recognizes that a sufficient storage area cannot be secured in the young generation area 42, the storage allocation unit 15 outputs a garbage collection execution command to the garbage collection processing unit 20 and executes the garbage collection in the data memory 40. Let When the collection of garbage in the data memory 40 is completed, the garbage collection processing unit 20 returns to the storage allocation unit 15 that the collection of garbage has been completed. Then, the storage allocation unit 15 secures an object storage area in the young generation area 42 after collecting the garbage, and returns the head address of the storage area to the instruction execution unit 14. If the storage allocation unit 15 recognizes that a sufficient storage area cannot be secured in the young generation area 42 even after collecting trash, the storage allocation unit 15 outputs a memory shortage message to a display or the like.

  Next, the operation content of the dust collection processing unit 20, in other words, the processing content by the execution of the dust collection processing program 32 will be described with reference to the flowchart shown in FIG.

  When the garbage collection control unit 23 of the garbage collection processing unit 20 receives the garbage collection execution command from the storage allocation unit 15, the survival rate prediction unit 25 sends the estimated survival rate of the young generation area 42 to the survival amount prediction unit 26. It is passed as ESR (S1). At this time, if the garbage collection execution command is received for the fifth time or later, for example, the survival rate prediction unit 25 passes the predicted survival rate predicted here as the ESR to the survival amount prediction unit 26, and receives the garbage collection execution command. For example, when the reception is less than the fifth time, the survival rate prediction unit 25 passes the preset prediction survival rate to the survival amount prediction unit 26 as ESR.

  Subsequently, the memory monitoring unit 22 measures the usage amount YU of the young generation area 42 and the free amount OF of the old generation area 43, and uses the usage amount YU of the young generation area 42 to the survival rate prediction unit 25 and the survival amount prediction unit 26. At the same time, the empty amount OF in the old generation area 43 is transferred to the dust collection control unit 23 (S2).

  When the survival amount prediction unit 26 receives the usage amount YU of the young generation region 42, the survival amount prediction unit 26 uses the usage amount YU and the predicted survival rate ESR of the young generation region 42 previously received to predict the predicted survival amount ES ( = YU × ESR), and the predicted survival amount ES is transferred to the dust collection control unit 23 (S3).

  When the garbage collection control unit 23 receives the predicted survival amount ES of the young generation region 42, the garbage collection control unit 23 compares the magnitude relationship between the previously received free amount OF of the old generation region 43 and the predicted survival amount ES of the young generation region 42 ( S4) If the predicted survival amount ES of the young generation area 42 is larger than the free capacity OF of the old generation area 43, the garbage collection execution unit 21 collects garbage of the old generation area 43 (S5) Garbage collection in the generation area 42 is executed (S6). On the other hand, if the predicted survival amount ES of the young generation area 42 is not larger than the free capacity OF of the old generation area 43, the garbage collection execution unit 21 starts collecting the garbage of the young generation area 42 (S7).

  Here, with reference to FIG. 16, the reason for comparing the size relationship between the free space OF in the old generation area 43 and the predicted survival amount ES in the young generation area 42, and the reason why the garbage collection execution target area differs depending on the comparison result. explain.

  Garbage collection performed in response to a garbage collection execution command from the storage allocation unit 15 basically moves objects that are reachable from the system among objects belonging to the young generation area 42, that is, live objects to the old generation area 43, The object is to not leave an object required by the system in the young generation area 42. For this reason, a predicted survival amount ES is obtained from the usage amount YU and the predicted survival rate ESR of the young generation area 42, and it is grasped whether or not objects corresponding to the predicted survival amount ES can be moved to a free area of the old generation area 43. Therefore, the magnitude relationship between the free space OF of the old generation area 43 and the predicted survival amount ES of the young generation area 42 is compared.

  If the predicted survival amount ES of the young generation region 42 is larger than the free amount OF of the old generation region 43, the objects corresponding to the predicted survival amount ES of the young generation region 42 cannot be moved to the free region of the old generation region 43. Then, the garbage collection of the old generation area 43 is executed (S5), and then the garbage collection of the young generation area 42 is executed (S6). On the other hand, if the predicted survival amount ES of the young generation area 42 is not large relative to the free capacity OF of the old generation area 43, the objects corresponding to the predicted survival amount ES of the young generation area 42 can be moved to the free area of the old generation area 43. Then, garbage collection in the young generation area 42 is started (S7).

  When the collection of garbage in the young generation area 42 is started, the object moves from the young generation area 42 to the old generation area 43, that is, the young generation object enters the old generation area 43. Therefore, the memory monitoring unit 22 confirms whether or not the free space of the old generation area 43 is sufficiently secured during the collection of garbage in the young generation area 42 (S8). When the memory monitoring unit 22 detects that the free space in the old generation area 43 is not sufficiently secured, the garbage collection control unit 23 causes the garbage collection execution unit 21 to temporarily suspend collection of garbage in the young generation area 42 ( S9) The garbage collection of the old generation area 43 is executed (S10). When the collection of garbage in the old generation area 43 is completed, the collection of garbage in the young generation area 42 is resumed (S11).

  When the collection of garbage in the young generation area 42 is completed (S6, S11, S12), the garbage collection execution unit 21 determines the amount of objects actually transferred from the young generation area 42 to the old generation area 43, that is, the objects in the young generation area 42. The survival amount of S is passed to the survival rate prediction unit 25 (S13).

  When the survival rate predicting unit 25 receives the survival amount S, the survival rate predicting unit 25 immediately before collecting the garbage from the usage amount YU of the young generation area 42 before the garbage collection received from the memory monitoring unit 22 in step 2 and the survival amount S. The object survival rate SR (= S / YU) of the young generation area 42 is obtained and stored (S14). The object survival rate SR obtained this time and the object survival rate SR obtained in the past four times of garbage collection are statistically processed to predict the survival rate ESR of the young generation area 42 immediately before the next dust collection (S15). ). This predicted survival rate ESR is used in Step 1 of the next dust collection process.

  As a method for obtaining the predicted survival rate ESR from the past survival rate SR, a method of setting the average value of the survival rates SR for the past five times as a predicted survival rate, or the maximum of the survival rates SR for the past five times is predicted. Various methods such as a method of setting the survival rate, a method of regarding the distribution of the survival rate for the past five times as a normal distribution, and setting the survival rate corresponding to 80% as the predicted survival rate are conceivable. Here, the predicted survival rate is calculated from the survival rate for the past 5 times in total, but for example, the survival rate for the past 1 time, that is, the survival rate obtained by the garbage collection performed immediately before is weighted and predicted. It is good also as a survival rate, and you may make it obtain | require an estimated survival rate from the survival rate for 2 times-4 times, and also 6 times or more.

  Further, here, for simplicity of explanation, the heap area 41 of the data memory 40 is divided into two, a young generation area 42 and an old generation area 43, but an older generation area is set, that is, the heap area 41 May be divided into three or more. If the heap area 41 is divided into three, and the first generation area, the second generation area, and the third generation area are set in ascending order, the garbage collection processing unit 20 receives a garbage collection execution command from the storage allocation unit 15. First, the predicted survival amount of the first generation area is obtained (S3), the magnitude relationship between the predicted survival amount and the free space of the second generation area is compared (S4), and the first Garbage collection (S8 or S5) of the generation area or the second generation area is performed. When garbage collection of the second generation area is to be performed, the predicted survival amount of the second generation area is obtained (S3), and the magnitude relationship between the predicted survival amount and the free space of the third generation area is compared ( In step S4, garbage collection (S8 or S5) in the second generation area or the third generation area is performed according to the comparison result.

  Next, the data structure of the object will be described with reference to FIG.

  The object has a header 50 and a payload 55. The header 50 is a part for storing data necessary for the processing system to manage the object, and basically cannot be directly operated from the user program. On the other hand, the payload 55 stores data used by the user program for execution of processing, and can be directly operated from the user program. The header 50 stores a reachability field 51 for storing a mark indicating whether or not the object can be reached from the root, and a mark for determining whether or not the object has been moved by copying. A moved field 52, a destination field 53 in which the destination address of the object is stored, and a size field 54 in which the size of the object is stored. As described above, the object in which the mark is stored in the reachability field 51 is an object that can be reached from the root, and is an object that is copied to the old generation area by garbage collection. Objects that are not marked in the possibility field 51 are garbage. All marks attached to the reachability field 51 are erased after the collection of garbage.

  It depends on the system which part of the header 50 the reachability field 51, the moved field 52, the destination field 53, etc. are taken. Since these fields are not used except during garbage collection, they are often used in combination with other fields that are required only during normal use. For example, when an area for 32 bits is secured as the movement destination field 53, the lower 2 bits of the movement destination field 53 are always 0, so the reachability field and the moved field are arranged in the lower 2 bits, When acquiring the destination, the lower 2 bits may be returned to 0 and acquired, and when the destination is written, the lower 2 bits may be left as they are.

  The payload 55 includes pointer fields 56, 57 and 59 and a data field 58. The pointer fields 56, 57, and 59 store the start addresses of other objects that have a reference relationship with the object. When collecting garbage, the object at the address stored in the pointer field 58 is traced. The data field 58 stores values other than pointers, such as integers and moving decimal numbers.

  Here, for convenience of the following explanation, when the pointer p is a variable indicating an object, the “object P” is “an object indicated by the pointer p”. Further, if X is a field of an object, “X of P” means “field X of object P”. The value written in the pointer field X is called “X value”.

  Next, the contents of the dust collection process (S6, 7) in the young generation area 42 will be described.

  As a basic method of garbage collection processing, there are a mark sweep method, a copy method, a mark compact method, etc. as described in Non-Patent Documents 1 and 2 shown in the “Background Technology” column. Adopt a copy method. Needless to say, a method other than the copy method may be adopted as a method for collecting dust in the young generation area 42.

  In the young generation garbage collection process (S6, 7), as shown in the flowchart of FIG. 4, the garbage collection execution unit 21 first performs an initialization process (S100). In this initialization process, as shown in FIG. 17A, the global variables scan and free are used as the head addresses of the old generation free area OF. When collecting the garbage in the young generation area 42 by the copy method, in this copy system, as shown in FIG. 16, the area corresponding to “From” is the busy area YO of the young generation area 42, and the area corresponding to “To” is the old generation area 43. Free area OF. That is, by collecting garbage in the young generation area, all the objects that survive in the in-use area YO of the young generation area 42 are moved to the empty area OF in the old generation area. The global variables necessary for this processing are the above-mentioned scan and free.

  When the initialization process (S100) ends, the garbage collection execution unit 21 performs the route process (S200). The root is a position (address) that is a starting point when accessing an object. This route value is stored in a CPU register or the like. This route processing is to copy the object indicated by the route to the old generation area 43.

  When the route collection (S200) ends, the dust collection execution unit 21 performs a scan process (S300). This scan processing is to copy an object that has a reference relationship with the object copied in the above-described root processing to the old generation area 43. Therefore, in the above-described route processing and this scan processing, all the objects that can be reached from the route, in other words, all the living objects are copied to the old generation area 43.

  Next, detailed processing of the route processing 200 will be described with reference to the flowchart shown in FIG. In this route processing, copy processing is performed on each object indicated by all routes, and the value of each route is rewritten with the result. The dust processing execution unit 21 first checks whether there is a route that has not yet been processed (S201). As a result, when there is an unprocessed route, one unprocessed route is taken out, the value is set as R (S202), and the copy process is called with this R as an argument (S203). Subsequently, R is rewritten to the return value of this copy process. Thereafter, the process returns to the determination process in step 201 again. If there is no unprocessed route, the route process is terminated.

  Next, the copy process (S400) called in step 203 of the previous route process 200 will be described with reference to the flowchart of FIG.

  The garbage collection execution unit 21 first substitutes the value received as the argument R of the copy process into the variable P (S401). Then, it is checked whether or not the moved field 52 of the object having P as the start address is marked, that is, whether the object has been moved after the copy process has been completed (S402).

  If the moved field 52 of the object having P as the head address is marked, the value stored in the destination field 53 of the object having P as the head address is returned as the return value of the copy process. (S408), the copy process is terminated.

  If the moved field 52 of the object having P as the head address is not marked, the free value set in the initialization process (S100) is substituted into the variable addr (S403), and P is the head address. Is copied to an area starting from the address pointed to by free (S404). Next, the free value is increased by the size of the copied object (S405). As a result, free points to the start address of the unused area of the old generation area. That is, free is a variable indicating the tail address of the object moved by the copy process. Subsequently, the moved field 52 of the copy source object is marked, and the value of addr is written in the destination field 53 of the copy source object. (S406). Then, the value of addr is returned as the return value of the copy process (S407), and the copy process is terminated.

  For example, as shown in FIG. 17A, objects a, b, and c are stored in the young generation area 42 of the heap area, and objects d, e, and f are stored in the old generation area 43, and the root field 61 , 62 stores “1” and “4”. Also, the start addresses of the objects a, b,..., And f and the start addresses of the empty areas of the old generation area 43 are 1, 2, 3, 4, 5, 6, and 7, respectively. Then, it is assumed that scan and free are set in the start address “7” of the empty area of the old generation area 43 in the initialization process (S100) of the dust collection process of the young generation area 42. Here, for convenience, there is only one pointer field 56, but there may be a plurality of pointer fields as described with reference to FIG. Here, in order to simplify the following description, the object sizes are all the same, but the size may be different for each object.

  When the route “1” is extracted from the route fields 61 and 62 in step 202 of the route processing 200 described above and becomes the argument R, and the copy processing is called with the argument R (= 1), the copy processing 400 In step 401, the argument R (= 1) is assigned to the variable P. In step 402, it is checked whether or not the moved field 52 of the object a having the variable P (= 1) as the start address is marked. . In this case, since the moved field 52 of the object a is not marked, the process proceeds to step 403, and the free value (= 7) is substituted for the variable addr (S403), as shown in FIG. Then, the object a having P (= 1) as the head address is copied to the area starting with the address “7” pointed to by free (S404). Next, the value of free is increased by the size of the copied object (S405). Then, the moved field 52 of the copy source object a is marked, the value of addr (= 7) is written to the movement destination field 53 of the copy source object a, and the route value of the route field 61 is further written. “1” is rewritten to “7” which is the address of the copy destination of the object a (S406). Then, the value of addr (= 7) is returned as the return value of the copy process (S407), and the copy process ends.

  Next, detailed processing of the scan processing (S300) will be described according to the flowchart shown in FIG.

  In this scan process (S300), the copy process (S400) described above with reference to FIG. 6 is sequentially executed on the pointers stored in the pointer fields of all copy destination objects, and the pointer value is the return value of the copy process. Is updated. Specifically, the dust collection execution unit 21 first checks whether the address indicated by scan is smaller than the address value indicated by free (S301). If it is smaller, it is checked whether there is a pointer field that has not yet been processed in the object having the start address as the address pointed to by scan (S302). When an unprocessed pointer field is found, one value p of this unprocessed pointer field is extracted (S303), and the copy process (S400) shown in FIG. 6 is called using this p value as an argument (S304). That is, in the copy process (S400) in the scan process (300), the pointer field of the object copied to the old generation area in the root process (S200) is examined, and the pointer value stored in this pointer field is used as the start address. The object to be copied is copied to the address indicated by free. When the copy process ends, the return value of this copy process is written as the value of p (S305). Then, the process returns to the determination process in step 302.

  If it is determined in step 302 that there is no unprocessed pointer field, a value obtained by adding the size of the object indicated by scan to the value of scan is set as a new address indicated by scan. That is, the address pointed to by scan is set to the head address of the next object (S306). Therefore, this variable scan can be said to be a variable indicating the address of the location where the scanning process is completed. When this processing (S306) is completed, the process returns to step 301 again to check whether the address indicated by scan is smaller than the address value indicated by free. If it is determined that the address indicated by scan is not smaller than the address value indicated by free, scan is performed. End the process.

  In this scan process (S300) following the above-described route process (S200), the collection of garbage of the younger generation is completed.

  Here, a specific example of the scanning process (S300) will be described with reference to FIGS.

  FIG. 18 (g) will be described in detail later. In the flowchart of FIG. 3, the collection of young generation garbage is started (S7), and there is no space in the old generation area during the scanning process (S8). ), The collection of young generation garbage is interrupted (S9), and the heap area at the stage where the collection of old generation garbage (S10) is completed is shown. When the old generation garbage collection (S10) is completed, the young generation garbage collection is resumed (S11). In this case, the scanning process interrupted in the middle is resumed. At the stage when this scanning process is resumed, the address indicated by scan and the address indicated by free are “6” and “7”, respectively, as shown in FIG.

  In this scan process (S300), the dust collection execution unit 21 first checks whether the address (= 6) indicated by scan is smaller than the address (= 7) indicated by free (S301). In this case, since scan is smaller, it is checked whether or not there is a pointer field 56 that has not yet been processed in the object a having the start address as the address pointed to by scan (S302). In this case, since there is an unprocessed pointer field 56, the value (= 3) of this unprocessed pointer field 56 is extracted (S303), and the copy process (S400) is called using this value as an argument (S304). In this copy process (S400), the object c having the argument (= 3) as the head address is copied to the position of free (= 7) (S404), the address indicated by free is changed to “8” (S405), A mark is put on the moved field of the object c at the movement source, and the value (= 7) of the movement destination address is written in the movement destination field (S406). When the copy process (S400) ends, the process returns again to step 302, where it is determined that there is no pointer field 56 that has not yet been processed in the object a having the address pointed to by scan as the head address.

  Then, the value of scan is updated to a new value (= 7) (S306), and the process returns to step 301, where it is determined that the address (= 7) indicated by scan is not smaller than the address (= 7) indicated by free. Then, the scanning process ends. As a result, the collection of garbage for the young generation is completed.

  Next, the old generation garbage collection processing (S5, 10) will be described with reference to the flowchart shown in FIG.

  In this old generation garbage collection, the mark compact method using the Lisp2 algorithm described in Non-Patent Documents 1 and 2 shown in the “Background Technology” column is adopted. Needless to say, a method other than the mark compact method may be adopted as an old generation garbage collection method.

  In the old generation dust collection process (S5, 10), the dust collection execution unit 21 first performs a mark process (S500). In this mark processing, the reachability fields of all objects that are reachable from the root among the objects existing in the old generation area are marked. At this time, the processing is performed by regarding the pointer of the object existing in the young generation area as the root.

  A specific example of the mark processing will be described with reference to FIGS.

  FIG. 17B shows the heap area at the stage where the route processing in the young generation garbage collection has been completed, as described above. When the route processing is completed, as described above, the object a moved by the route processing is scanned, and the object having the pointer value stored in the pointer field of the object a as the head address is located at the address indicated by free. Try to copy. However, in this case, since there is no space in the old generation area, in the flowchart shown in FIG. 3, it is determined that there is no space in the old generation area (S8) during the collection of garbage of the young generation (S7). The generational garbage collection is interrupted (S9), and the old generation garbage collection is started (S10). In the mark process (S500) of the old generation garbage collection (S10), as described above, the reachability fields of all objects that can be reached from the root are marked in the objects in the old generation area. In this case, since “7” and “4” are stored as route values in the route fields 61 and 62, the moved object a having “7” as the head address, and the object having “4” as the head address Each reachability field 51 of d is marked. Further, the object “c” having “3” stored in the pointer field 56 of the marked object “a” as the head address, and “6” stored in the pointer field 56 of the marked object “d” are headed. A mark is attached to each reachability field 51 of the object f as an address.

  Returning to the description of the flowchart of FIG.

  When the mark processing (S500) ends, the garbage collection execution unit 21 determines the destinations of all the live objects existing in the old generation area (S600), and corrects the memory contents (S700). This memory content correction process is a process for correcting the contents of the header of an object accompanying the movement of each object. Thereafter, the garbage collection execution unit 21 moves the surviving objects existing in the old generation area to the movement destination determined in the movement destination determination process (S600) (S800), and ends the old generation garbage collection. Note that “move” in the object move process in step 800 is a move in a narrow sense that does not include a case where an object remains at the move source as in the above-described copy process.

  Next, the destination determination process (S600) will be described with reference to the flowchart shown in FIG.

  In this movement destination determination process (S600), as described above, the movement destination addresses of all the living objects existing in the old generation area are determined, and further, the movement destination fields determined in the movement destination field of the object are determined. The address is written. Specifically, the garbage collection execution unit 21 first sets free and P to point to the start address of the old generation area (S601). P indicates an object that is currently the target of the movement destination determination process, and free indicates a movement destination when the object is moved. Subsequently, it is checked whether P is less than the tail address of the in-use area of the old generation area (S602). If P is less than the tail address of the used area of the old generation area, it is checked whether or not the reachability field of the object having P as the head address is marked (S603). If it is marked, it means that this object is alive, so write the free value in the destination field of this object, add the size value of this object to the free value, The value is set to free (S604), and the process proceeds to step 605. On the other hand, if it is determined in step 603 that the mark is not attached, this means that the object is not alive, so that the object is not moved and the process immediately proceeds to step 605. In step 605, the size of the object having the P value as the start address is added to the P value, and this is used as the new P value (S604). Next, returning to the determination process of step 602 again, if it is determined that P is not less than or equal to the tail address of the used area of the old generation area, the movement destination determination process ends. Although not described above, in order to speed up the processing after the next phase, when objects that are not marked in the reachability field continue, processing is performed in which they are considered as one object. It is also possible.

  A specific example of the destination determination process (S600) will be described with reference to FIGS.

  FIG. 17C shows the heap area at the stage where the mark processing (S500) in the collection of old generation garbage has been completed, as described above. When this mark process is completed, a move destination determination process (S600) is started, and both free and P are set to point to the top address (= 4) of the old generation area 43 (S601). If P is less than the tail address of the used area of the old generation area 43 (S602), it is checked whether or not the reachability field 51 of the object d having P (= 4) as the head address is marked ( S603). In this case, the reachability field 51 of the object d is marked, but since it is stored at the beginning of the old generation area 43, it is not set as a movement target. Then, the value of the size of the object d is added to the value of free, and this is set as a new value of free (= 5) (S604), and the size of the object d having the value of P as the start address is added to the value of P. This is the new value of P (= 5) (S604). That is, free and P are set so as to point to address 5, respectively. Again, after returning to step 602, the process proceeds to step 603, where it is checked whether or not the reachability field 51 of the object e having P (= 5) as the head address is marked. Since the reachability field 51 of this object e is not marked, which means that the object e is not alive, it does not become a movement target, and immediately proceeds to step 605. In step 605, the size of the object e having the P value as the start address is added to the P value, and this is set as a new P value (= 6).

  Thereafter, the process returns to step 602 and then proceeds to step 603, where it is checked whether or not the reachability field 51 of the object f having P (= 6) as the head address is marked. Since the reachability field 51 of this object f is marked, after the value of the destination field 53 of this object f is set to the free value (= 5), the free value is updated to 6 (S604). ). Then, after updating the value of P to 7 (S605), the process returns to step 602 and then proceeds to step 603. Also in this case, it is checked whether or not the reachability field 51 of the object a having P (= 7) as the head address is marked. Since the reachability field 51 of this object a is also marked, after the value of the destination field 53 of this object a is set to the free value (= 6), the free value is updated to 7 (S604). ). Then, after updating the value of P to 8 (S605), the process returns to step 602 again. In this step 602, since the value of P (= 8) is the tail address (= 8) in use of the old generation area 43, the movement destination determination process is terminated. That is, here, the destination of the object f is determined as the address 5 and the destination of the object a is determined as the address 6.

  Next, the memory content correction process (S700) will be described with reference to the flowchart shown in FIG.

  As the memory content correction processing, the garbage collection execution unit 21 first performs the young generation memory content correction processing (S710), and then performs the root field memory content correction processing (S740) and the old generation memory content correction processing 1 ( S750) is performed in order.

  Next, according to the flowchart shown in FIG. 11, the details of the memory content modification processing (S710) of the young generation will be described.

  In the memory generation modification process (S710) of the young generation, when the moved field is not marked for all the objects of the young generation, the value of the pointer field in the object is set to the movement destination of the object indicated by the pointer. Correct to the value of the field. When the moved field is marked, the object's destination field is updated to the value of the destination field of the object entity pointed to by the destination, and the object reachability field is marked. The mark in the reachability field of the young generation object indicates that the object destination field has already been updated with the entity destination. Since the moved field of the object is marked only when the young generation area is suspended (S9 in FIG. 3), only when the old generation area garbage collection processing is called in S10 of FIG. is there.

  In this young generation memory content correction process (S710), the garbage collection execution unit 21 first substitutes the start address of the young generation area for S (S711). S is a pointer pointing to the object whose memory contents are currently being modified. Next, it is checked whether the address indicated by S is less than the tail address of the in-use area of the young generation area (S712). If the address indicated by S is less than the tail address of the in-use area of the young generation area, it is checked whether or not the moved field of the object having the address indicated by S as the head address is marked (S713). If it is marked, go to Step 714 or Step 718. The processing from step 714 to step 717 is executed only when garbage collection of the young generation area is interrupted (S9 in FIG. 3). Proceed to 718. In step 714, Q is a value stored in the destination field of the object whose head address is the address indicated by S. Next, a destination acquisition process (S730) described later is called with this Q as an argument (S715), and the return value of the destination acquisition process is set to Q, that is, the return value Q is written in the destination field (S716). The return value of the movement destination acquisition process is the movement destination of the entity of the object whose head address is the address indicated by S. Next, the reachability field of the object having the address indicated by S as the head address is marked (S717). The reason why the mark is added here is to distinguish that the value of the movement destination field of the object is the movement destination of the entity.

  When the reachability field is marked (S717), the size of the object having the address indicated by S as the head address is added to the value of S, and this is set as the new value of S (S718). This is a process of moving the object to be processed to the next object. When this process ends, the process returns to the determination process of step 712. If it is determined in step 712 that the address indicated by S is not less than the trailing address of the in-use area of the young generation area, the memory content correction process for the young generation is terminated.

  If it is determined in step 713 that the moved field of the object having the address indicated by S as the head address is not marked, it is checked whether an unprocessed pointer field exists in this object (S719). . If there is no unprocessed pointer field, the process proceeds to step 718 described above. If there is an unprocessed pointer field, the value of this unprocessed pointer field is fetched (S720), and a later-described destination acquisition process is called using the pointer field value p as an argument (S721). ), The return value of the destination acquisition process is written in the pointer field (S722), and the process returns to step 719.

  Next, the destination acquisition process (S730) will be described with reference to the flowchart shown in FIG.

  This destination acquisition process (S730) is called in the processes of step 715 and step 721 in FIG. In the move destination acquisition process, if the object pointed to by the argument is moved by the compaction process, the value of the move destination field is returned; otherwise, the argument is returned as it is. However, if the object has a moved field marked, it is indicated by the value of the destination field of this object because the entity of this object has already been moved to a different location due to garbage collection of the younger generation. Returns the value of the destination field of the current object. If both the moved field and reachability field of the object are marked, the object's destination has already been rewritten to the entity's destination, so that value is returned.

  In this movement destination acquisition process (S730), the garbage collection execution unit 21 first substitutes an argument for P (S731). Next, it is checked whether or not the reachability field of the object having P as the head address is marked (S732). If there is a mark, the value of the destination field of this object is set as a return value (S733), and the process ends. If there is no mark, it is checked whether or not this object's destination field is marked (S734). If there is no mark, the value of P is set as a return value (S737), and the process ends. That is, in this case, the value given as an argument becomes the return value as it is. If the mark is attached, the process itself is called with the value of the destination field of this object as an argument (S735), and the return value from the called process is the return value in this destination acquisition process ( S736), the process is terminated.

  A specific example of the memory content modification process (S710) of the young generation and the migration destination acquisition process (S730) executed in this process will be described with reference to FIGS. 17 (d) and 18 (e).

  FIG. 17D shows the heap area at the stage where the movement destination determination process (S600) is completed as described above. When this move destination determination process ends, the young generation memory correction process (S710) is started, and the head address of the young generation area 42 is substituted into S (= 1) (S711). Next, it is checked whether the address indicated by S (= 1) is less than the tail address of the in-use area of the young generation area 42 (S712). In this case, since the address indicated by S is less than the tail address of the in-use area of the young generation area, it is checked whether or not the moved field 52 of the object a having the address indicated by S as the head address is marked ( S713). In this case, since there is a mark, the value stored in the movement destination field of the object a having the address indicated by S as the head address is substituted for Q (= 7) (S714). Next, the destination acquisition process (S730) is called using this Q as an argument (S715).

  In the called destination acquisition process (S730), first, an argument Q (= 7) is substituted for P (S731). Next, it is checked whether or not the reachability field 51 of the object a having P (= 7) as the head address is marked (S732). In this case, since there is a mark, the value (= 6) of the destination field of this object a is set as a return value (S753), and the destination acquisition process is terminated.

  After calling the movement destination acquisition process in step 715, the return value (= 6) from this movement destination acquisition process is set to Q. That is, as shown in FIG. 18 (e), the return value (= 6) is set to the object a. Is written in the destination field 53 of the destination (S716). Next, the reachability field 51 of the object a having the address of S (= 1) as the head address is marked (S717). Then, the size of the object a having the address of S as the head address is added to the value of S (= 1), and this is set as a new value of S (= 2) (S718), that is, the memory content correction processing target To the object b having the value of S as the head address, and the process returns to the determination processing in step 712. Then, after steps 713 and 719, the value of S is updated to a new value (= 3) in step 718, and the process returns to step 712 again.

  After returning to step 712 and reaching step 713, since the moved field 53 of the object c having the address indicated by S (= 3) as the head address is not marked here, the steps 719 and 720 are performed. move on. In step 720, the value p (= 1) of the pointer field 56 of the object c having the address of S (= 3) as the head address is extracted, and the destination acquisition process ( S730) is called (S721).

  In the called destination acquisition process (S730), first, an argument p (= 1) is substituted for P (S731). Next, it is checked whether or not the reachability field 51 of the object a having P (= 1) as the head address is marked (S732). In this case, since there is a mark, the value (= 6) of the destination field of this object a is set as a return value (S753), and the destination acquisition process is terminated.

  After calling the destination acquisition process in step 721, the return value (= 6) from this destination acquisition process is set to Q, that is, the return value (= 6) is set to the object c as shown in FIG. Is written in the destination field 53 of the destination (S716). Next, the reachability field 51 of the object c having the address of S (= 3) as the head address is marked (S717). Since the reachability field 51 of the object c is already marked, the mark is overwritten. Then, the value of S (= 3) is changed to a new value of S (= 4) (S718), and the process returns to step 712 again.

  In this step 712, since the value of S (= 4) is the tail address of the in-use area of the young generation area 42, the value of S (= 4) is not less than the tail address of the in-use area of the young generation area 42. It is determined that the memory content correction process for the younger generation is terminated.

  Next, the route memory content correction process (S740) will be described with reference to the flowchart shown in FIG.

  In this memory content correction process (S740), the contents are corrected in order for all routes. The garbage collection execution unit 21 first checks whether an unprocessed route remains (S741). If not, the process is terminated. If it remains, one unprocessed route is taken out and this route value is set as R (S742). Next, the above-mentioned destination acquisition process (S730) is called with R as an argument (S743). Then, the return value from the movement destination acquisition process is substituted for R, that is, written in the route field (S744), and the process returns to step 741. The global variable scan is also treated as a root in the route memory modification process. On the other hand, free is not treated as a root.

  Next, the old generation memory content correction processing (S750) will be described with reference to the flowchart shown in FIG.

  In this old generation memory content correction process (S750), the value of the pointer field is corrected to the destination of the object pointed to by the pointer for each object of the old generation. First, the garbage collection execution unit 21 substitutes the head address of the old generation area for P (S751). This P is a pointer that points to the object whose memory contents are currently being modified. Next, it is checked whether P is less than the tail address of the old generation busy area (S752). If P is not less than the tail address of the old generation in-use area, the memory content correction has been completed for all objects in the old generation area, so the memory content correction processing for the old generation area is terminated. On the other hand, if P is less than the tail address of the old generation in-use area, it is checked whether the reachability field of the object having P as the head address is marked (S753). If there is a mark, it is checked whether there is an unprocessed pointer in the object pointed to by P (S754). If there is an unprocessed pointer, one value of the unprocessed pointer field of the object pointed to by P is extracted and set as Q (S755). Then, using the Q value as an argument, the above-mentioned destination acquisition process (S730) is called (S756), and the Q value is updated to the return value from this destination acquisition process. That is, the return value is written in the pointer field of the object pointed to by P (S757), and the process returns to step 754. If it is determined in step 753 that the reachability field of the object having P as the start address is not marked, and if there is no unprocessed pointer in the object pointed to by P in step 754, the point indicated by P The size of the object is added to the object to set this value as a new value of P (S758), and the process returns to step 752.

  The memory content correction processing (S700) is completed in the above-described young generation memory content correction processing (S710), root memory content correction processing (S740), and old generation memory content correction processing (S750).

  Here, an example of a specific route memory content correction process (S740) and an old generation memory content correction process (S750) will be described with reference to FIG. 18 (e) and FIG. 18 (f).

  FIG. 18E shows the heap area at the stage when the young generation memory content correction processing (S710) is completed, as described above. When this young generation memory content correction processing is completed, the root memory correction processing (S740) is started. In the memory content correction processing of this route, an unprocessed route, in this case, the value of the route field 61 (= 7) is taken out, and this value is set to R (S741, 742). Next, the destination acquisition process (S730) is called with this R (= 7) as an argument (S743).

  In the called destination acquisition process (S730), first, an argument p (= 7) is substituted for P (S731). Next, it is checked whether or not the reachability field 51 of the object a having P (= 7) as the head address is marked (S732). In this case, since there is a mark, the value (= 6) of the destination field of this object a is set as a return value (S753), and the destination acquisition process is terminated.

  After calling the destination acquisition process in step 743, the return value (= 6) from this destination acquisition process is set to R. That is, as shown in FIG. 18 (f), the value of the route field 61 is set to the return value ( = 6) (S744). In this route memory content correction processing, scan and free are also handled as routes, and processing similar to that for routes is performed. For this reason, scan indicates the address “6”, and free indicates the address “7”. This completes the route memory content correction process.

  Subsequently, an old generation memory content correction process (S750) is started. In the memory content correction process for the old generation, first, the start address (= 4) of the old generation area is substituted for P (S751). Next, if P is less than the tail address of the old generation in-use area (S752), it is checked whether the reachability field 51 of the object d having P (= 4) as the head address is marked (S753). ). In this case, since there is a mark, it is further checked whether there is an unprocessed pointer in this object d (S754). In this case, since there is an unprocessed pointer, the value (= 6) of the unprocessed pointer field of this object c is extracted and set as Q (S755). Then, the destination acquisition process (S730) is called using the Q value as an argument (= 6) (S756).

  In the called destination acquisition process (S730), first, an argument p (= 6) is substituted for P (S731). Next, it is checked whether or not the reachability field 51 of the object f having this P (= 6) as the head address is marked (S732). In this case, since there is a mark, the value (= 5) of the destination field of this object f is set as a return value (S753), and the destination acquisition process is terminated.

  After the movement destination acquisition process is called in step 756, the return value (= 5) from this movement destination acquisition process is set to Q. That is, as shown in FIG. = 5) (S757), and the process returns to Step 754. Thereafter, the process returns to step 752 via step 758. Thereafter, the processing of steps 752 to 758 is repeated for the remaining objects e, f, and a, but the pointer field 56 of the objects e, f, and a is not changed.

  Next, the object movement process (S800) will be described with reference to the flowchart shown in FIG.

  This object movement processing is processing for actually moving an object to the destination address determined in the previous destination determination processing (S600).

  In this object movement process (S800), the garbage collection execution unit 21 first substitutes the top address of the old generation area for P (S801). This P indicates an object to be moved. Next, it is checked whether the address P is less than the tail address of the in-use area of the old generation area (S802). If the address P is less than the tail address of the used area of the old generation area, is there a mark in the reachability field of the object with P as the start address, and whether a value is stored in the destination field of this object? (S803). If there is a mark in the reachability field of this object and a value is stored in the destination field of this object, the value of the destination field of this object is considered as an object to be moved. In addition, the reachability field mark and the destination field value of this object are deleted (S804). Subsequently, this object is moved to the free position (S805). Note that the “move” in the object move process is not a move in which an object remains at the move source as in the copy process, as described above. However, in this application, unless otherwise specified, “move” refers to a movement in which an object remains in the movement source, such as a copy process, and a movement in which an object does not remain in the movement source, such as a movement in the object movement process. Is also included. Then, by adding the size of P to P, the object to be processed is advanced to the next object (S806), and the process returns to step 802. Similarly, when it is determined in step 803 that there is no mark in the reachability field of the object having P as the head address or no value is stored in the destination field of this object, After adding the size of P (S806), the process returns to step 802.

  If it is determined in step 802 that the address P is not less than the trailing address of the used area of the old generation area, the size of P is added to P (S807), and the object movement process is terminated.

  The above-described mark processing (S500), movement destination determination processing (S600), memory content correction processing (S700), and object movement processing (S800) complete the collection of old generation garbage.

  Here, a specific example of the object movement process (S800) will be described with reference to FIG. 18 (f) and FIG. 18 (g).

  FIG. 18F shows the heap area at the stage where the memory content correction process (S700) is completed as described above. When this memory content correction process ends, an object movement process (S800) is started. The garbage collection execution unit 21 first substitutes the top address of the old generation area 43 for P (S801). Next, it is checked whether the address P (= 4) is less than the tail address of the used area of the old generation area 43 (S802). If the address P is less than the tail address of the used area of the old generation area, there is a mark in the reachability field 51 of the object d having P (= 4) as the head address, or the destination field of this object d It is checked whether a value is stored in 53 (S803). Since no value is stored in the destination field 53 of the object d, the size of P is added to P (S806), and the process returns to step 802.

  Similarly, Step 803 to Step 806 are executed for the object e having P (= 5) as the head address, and the target object is changed to the object f. Since this object f has a mark in its reachability field 51 and a value is stored in the destination field 53 of this object f (S803), it is determined that this object f is a movement candidate and free is set. In addition to the value (= 5) of the destination field 53 of this object f, the mark of the reachability field and the value of the destination field of this object f are erased (S804). Subsequently, as shown in FIG. 18G, the object f is moved to the position of free (= 5) (S805). Note that “scan” and “free” in FIG. 18G are not related to the object movement process, but are for the scan process, as will be described later. Thereafter, the object to be processed is advanced to the next object a (S806), and the process returns to step 802.

  Since this object a has a mark in its reachability field 51 and a value is stored in the destination field 53 of this object a (S803), it is assumed that this object a is also a movement candidate, and free is set. In addition to changing to the value (= 6) of the destination field 53 of this object a, the mark of the reachability field and the value of the destination field of this object a are deleted (S804). Subsequently, the object a is moved to the position of free (= 6) (S805). Then, after adding the size of P to P (S806), the process returns to step 802.

  In step 802, it is determined that the address P (= 7) is not less than the tail address of the in-use area of the old generation area 43, the size of P is added to P (S807), and the object movement process is terminated. As a result, the old generation garbage collection (S10) ends.

  This old generation garbage collection (S10) is a process performed after interruption (S9) in the scan process of the young generation garbage collection as described above with reference to FIG. When the collection (S10) is completed, the interrupted scan process for collecting the young generation's garbage is resumed (S11). In this scan process, as a specific example of the scan process, as described above with reference to FIG. 18H, the object c starting from the address value “3” is copied to the position of the address “7”. Garbage collection ends. When the collection of garbage of the young generation is completed in this way, only the objects a and c whose entities have moved to the old generation area 43 and the object b that cannot be accessed from the system, that is, the object b that is not alive, are included in the young generation area 42. Will remain. As a result, since only the unnecessary objects exist in the young generation area 42, new objects can be stored in the entire area of the young generation area 42 thereafter.

  As described above, in the present embodiment, the amount of objects transferred from the one or more objects stored in the young generation area 42 to the old generation area 43 when collecting the garbage in the young generation area 42, that is, young The survival amount ES of the generation is predicted from the past collection results of the young generation area 42, and the amount of movement is compared with the free capacity OF of the old generation area 43, and according to the result, the garbage collection of the old generation area 43 is collected. Therefore, the timing of collecting garbage in the old generation area becomes relatively accurate, the possibility of a system failure is reduced, and the performance degradation of the system can be suppressed. Further, when the old generation area 43 has no space for storing objects from the young generation area 42 during the collection of garbage in the young generation area 42, the collection of garbage in the young generation area 42 is temporarily interrupted. After the collection of the garbage in the generation area 43 is executed, the collection of the garbage in the young generation area 42 is resumed, so that the possibility of a system failure can be further reduced and the deterioration of the system performance can be suppressed.

[Second Embodiment]
A second embodiment will be described with reference to FIGS.

  In this embodiment, as in the first embodiment, all objects that survived garbage collection in the young generation area do not enter the old generation area, but collect one or more garbage in the young generation area. Only the surviving objects enter the old generation area.

  For this reason, in this embodiment, as shown in FIG. 19, the functional configuration of the dust collection processing unit 20a is different from that of the first embodiment. Specifically, as the amount of objects transferred from the young generation area to the old generation area, the survival amount ES of the objects in the young generation area is predicted in the first embodiment. Predict the promotion amount EP of the object to the old generation area. In the present embodiment, the configuration and operation of portions other than the dust collection processing unit 20a are the same as those in the first embodiment.

  In this embodiment, as described above, since only objects that survive one or more garbage collections in the young generation area enter the Hall of Fame, it is necessary to grasp the number of times the garbage collection survived a certain generation. . For this reason, as shown in FIG. 20, the object header 50 is present in addition to the reachability field 51, the moved field 52, the destination field 53, and the size field 54 as in the first embodiment. There is an age field 56a in which the age, which is the number of times that the collection of garbage in the generation area, has survived, is stored.

  As shown in FIG. 19, the heap area 41 of the data memory 40 is divided into a young generation area 42 a and an old generation area 43. The young generation area 42a is further divided into Eden 44, from 45, and to 46.

  As shown in FIG. 19, the garbage collection processing unit 20a includes a garbage collection execution unit 21a for collecting garbage in each of the young generation area 42a and the old generation area 43 of the data memory 40, and each of the areas 42a, 43. A memory monitoring unit 22 that measures the usage amount and free space of the computer, a predicted promotion amount calculation unit 27 that predicts an object promotion amount EP that enters the old generation region 43 from the young generation region 42a, and each of these units 21a, 22, And a dust collection control unit 23 for controlling 27. The predicted promotion amount calculation unit 27 measures the survival rate SR (= YS / YU), which is the ratio of the survival amount YS of the object that survived after collecting the dust to the area usage amount YU of the object before collecting the dust, and the past survival rate. The survival rate predicting unit 25 that predicts the current survival rate ESR from the SR results, and the promotion amount of the object that enters the old generation region 43 from the young generation region 42a with respect to the survival amount YS of the object that survived after collecting the garbage of the young generation Promotion rate PR (= YP / YS) which is the ratio of YP is measured, and the promotion rate prediction unit 28 for predicting the promotion rate EPR at the time of the next garbage collection from the past promotion rate PR results, and the predicted promotion From the predicted generation rate EPR and the current survival rate ESR of the young generation region 42a and the current usage amount YU of the young generation region 42a, the young generation region 42a to the old generation region 4 And a promotion amount prediction unit 29 for predicting the promotion of the object to be tenured EP (= EPR (YU · ESR)) to.

  When the memory allocation unit 15 receives an object memory allocation command from the instruction execution unit 14, the storage allocation unit 15 secures a storage area in the Eden 44 of the young generation area 42 a and returns the top address of this storage area to the instruction execution unit 14. If the storage allocation unit 15 recognizes that a sufficient storage area cannot be secured in the Eden 44 of the young generation area 42a, the storage allocation unit 15 outputs a garbage collection execution instruction to the garbage collection processing unit 20a, and collects the garbage in the data memory 40. Is executed.

  Next, the operation content of the dust collection processing unit 20a when receiving a dust collection execution command from the storage allocation unit 15, in other words, the processing content by the execution of the dust collection processing program 32 will be described with reference to the flowchart shown in FIG.

  When the garbage collection control unit 23 of the garbage collection processing unit 20a receives a garbage collection execution command from the storage allocation unit 15, the survival rate prediction unit 25 sets the predicted survival rate of the young generation area 42a as the ESR and the promotion amount prediction unit 29. And the promotion rate prediction unit 28 passes the predicted promotion rate of entering the hall of fame from the young generation region 42a to the old generation region 43 to the promotion amount prediction unit 29 as EPR (S1a). At this time, if the garbage collection execution command is received for the fifth time or later, for example, the survival rate prediction unit 25 passes the predicted survival rate predicted here as the ESR to the promotion amount prediction unit 29, and the promotion rate prediction unit 28 Passes the predicted promotion rate predicted here to the promotion amount prediction unit 29 as EPR. In addition, when the garbage collection execution command is received, for example, less than the fifth time, the survival rate prediction unit 25 passes the preset prediction survival rate as the ESR to the survival amount prediction unit 26, and the promotion rate prediction unit 28 The preset promotion rate set in advance is passed to the promotion amount prediction unit 29 as EPR.

  Subsequently, the memory monitoring unit 22 measures the usage amount YU of the young generation region 42a and the free space OF of the old generation region 43, and the usage amount YU of the young generation region 42a is sent to the survival rate prediction unit 25 and the survival amount prediction unit 26. At the same time, the empty amount OF in the old generation area 43 is transferred to the dust collection control unit 23 (S2). The usage amount YU here is the sum of the usage amount YOe of Eden 44 and the usage amount YOt of to46 in the young generation area 42a, as shown in FIG. It should be noted that the from 45 of the young generation area 42a is unused for the reason described later (however, there are objects that are not alive).

  Upon receiving the usage amount YU of the young generation region 42a, the promotion amount prediction unit 29 receives the predicted survival amount (=) of the young generation region 42a from the usage amount YU and the predicted survival rate ESR of the young generation region 42 previously received. ESR · YU) is obtained, and this predicted survival amount is multiplied by the predicted promotion rate EPR to obtain the predicted promotion amount EP (= EPR (ESR · YU)). Then, the predicted promotion amount EP is passed to the dust collection control unit 23 (S3a).

  When the garbage collection control unit 23 receives the predicted promotion amount EP of the young generation region 42a, the garbage collection control unit 23 compares the size relationship between the previously received free amount OF of the old generation region 43 and the predicted promotion amount EP of the young generation region 42a ( S4) If the predicted promotion amount EP of the young generation area 42a is larger than the free capacity OF of the old generation area 43, the garbage collection execution unit 21a executes the garbage collection of the old generation area 43 (S5) The garbage collection of the generation area 42a is executed (S6a). On the other hand, if the predicted promotion amount EP of the young generation area 42a is not larger than the free capacity OF of the old generation area 43, the garbage collection execution unit 21a starts collecting the garbage of the young generation area 42a (S7a).

  Here, with reference to FIG. 23, the reason for comparing the size relationship between the free space OF of the old generation area 43 and the predicted advancement amount EP of the young generation area 42a, and the reason why the execution target area of garbage collection differs depending on the comparison result. explain. FIG. 4A shows the state of the heap area before collecting garbage in the young generation area 42a, and FIG. 4B shows the state of the heap area after collecting garbage in the young generation area 42a.

  In the collection of garbage in the young generation area 42a, as described above, only objects that survive several times of garbage collection enter the old generation area 43. For this reason, the amount of objects that will be inducted into the old generation region 43 from the young generation region 42a, that is, the predicted promotion amount EP is obtained, and whether the objects corresponding to the predicted promotion amount EP can be moved to the free space of the old generation region 43. In order to ascertain whether or not, the magnitude relationship between the free space OF in the old generation area 43 and the predicted promotion amount EP of the young generation area 42a is compared.

  If the predicted promotion amount EP of the young generation area 42a is larger than the free capacity OF of the old generation area 43, objects corresponding to the predicted promotion amount EP of the young generation area 42a cannot be moved to the free area of the old generation area 43. Then, garbage collection of the old generation area 43 is executed (S5), and then garbage collection of the young generation area 42a is executed (S6a). On the other hand, if the predicted promotion amount EP of the young generation area 42a is not large relative to the free capacity OF of the old generation area 43, objects corresponding to the predicted promotion amount EP of the young generation area 42a can be moved to the free area of the old generation area 43. Then, garbage collection in the young generation area 42a is started (S7a).

  When the collection of garbage in the young generation area 42a is started, the object enters the old generation area 43 from the young generation area 42a. For this reason, as in the first embodiment, the memory monitoring unit 22 confirms whether or not a free space in the old generation area 43 is sufficiently secured during the collection of garbage in the young generation area 42a (S8). . When the memory monitoring unit 22 detects that the free space in the old generation area 43 is not sufficiently secured, the garbage collection control unit 23 causes the garbage collection execution unit 21a to temporarily suspend collection of garbage in the young generation area 42a ( S9) The garbage collection of the old generation area 43 is executed (S10). When the collection of garbage in the old generation area 43 is completed, the collection of garbage in the young generation area 42a is resumed (S11a).

  When the collection of garbage in the young generation area 42a is completed (S6a, S11a, S12), the garbage collection execution unit 21a moves the amount of objects actually transferred from the young generation area 42a to the old generation area 43, that is, from the young generation area 42a. The promotion amount is transferred to the survival rate prediction unit 25 and the promotion rate prediction unit 28 as YP. Further, the amount of all objects actually moved to other areas in the collection of garbage in the young generation area 42a, that is, the survival amount of objects in the young generation area 42a is passed to the promotion rate prediction unit 28 as YS (S13a). It should be noted that the amount of all objects actually moved to other areas by collecting garbage in the young generation area 42a, that is, the survival amount YS is actually from the young generation area 42a to the old generation area 43 as shown in FIG. The amount (YP (= YSt) + YSe) obtained by adding the amount (YSe) of the object actually transferred from one region in the young generation region 42a to another region to the promotion amount YP (= YSt) that is the amount of the transferred object ).

  When the survival rate predicting unit 25 receives the survival amount YS, the survival rate predicting unit 25 immediately before collecting the garbage from the usage amount YU of the young generation area 42a before the garbage collection received from the memory monitoring unit 22 in the previous step 2 and the survival amount YS. The object survival rate SR (= YS / YU) of the young generation area 42a is obtained and stored (S14). Then, the object survival rate SR obtained this time and the object survival rate SR obtained in the past four garbage collections are statistically processed to predict the survival rate ESR of the young generation area 42a immediately before the next garbage collection (S15). ). This predicted survival rate ESR is used in step 1a of the next dust collection process.

  Further, when the survival rate YS and the promotion amount YP are received in step 13a, the promotion rate prediction unit 28 obtains the promotion rate PR (= YP / YS) of the young generation region 42a using these values, and stores this. (S16). Then, the promotion rate PR obtained this time and the promotion rate PR obtained in the past four garbage collections are statistically processed to predict the promotion rate EPR at the time of the next garbage collection of the young generation region 42a (S17). . This predicted promotion rate EPR is used in step 1a of the next dust collection process.

  In addition, as the method for obtaining the predicted survival rate ESR from the past survival rate SR and the method for obtaining the predicted promotion rate EPR from the past promotion rate PR, the various statistical processing methods exemplified in the first embodiment can be considered.

  Next, the garbage collection process (S6a, S7a) of the young generation will be described.

  Also in this embodiment, the dust collection execution unit 21a performs the initialization process (S100), the route process (S200), and the scan process (S300) as shown in FIG. However, since the contents of the initialization process and the contents of the copy process in the route process and the scan process are different from those in the first embodiment, these contents will be described below.

  In the initialization process, the garbage collection execution unit 21a first sets the global variables scan and free as the head address of the old generation free area OF, as in the first embodiment. Next, as shown in FIG. 23, the current from45 is set to to46, and the current to46 is set to from45. As a result, the unused area changes from from 45 to to 46. Then, the initialization process is terminated with the variable scan to and the variable free to as the start address of the new to 46.

  In the route process (S200), as in the first embodiment, the copy process is called with the unprocessed route value as an argument (FIG. 5, S203), and in the scan process (S300), the unprocessed pointer value is set. Copy processing is called as an argument (FIG. 7, S304).

  In this copy process (S400a), the dust collection execution unit 21a first substitutes an argument from the route process or the scan process into P, similarly to the copy process (FIG. 6, S400) of the first embodiment (S401). ), It is determined whether or not the object having the value of P as the head address has been moved (S402). If the object having P as the start address has been moved, the value stored in the destination field 53 of the object having P as the start address is returned as the return value of the copy process (S408), and the copy process is performed. finish.

  On the other hand, if the object having P as the head address has not been moved, it is determined whether or not the age of this object is greater than a predetermined promotion age with reference to the age field 56a of this object (S410). . When the age of this object is larger than a predetermined promotion age, that is, as shown in FIG. 23A, in to 46 (from 45 after the initialization process) of the young generation area 42a before the garbage collection initialization process. If the object is a stored object, the same processing as in step 403 to step 405 of the first embodiment is performed. That is, the value of free set in the initialization process is substituted into the variable addr (S403), the object having P as the head address is copied to the area starting with the address pointed to by free (S404), and the value of free is set. The size is increased by the size of the copied object (S405). Then, the value of the age field 56a of this object is set to 0 (S411).

  On the other hand, if it is determined in step 410 that the age of this object is not greater than the predetermined promotion age, that is, as shown in FIG. 23A, the Eden 44 of the young generation area 42a before the garbage collection initialization process is performed. If the object is stored in, the value of free to set in the initialization process is substituted into the variable addr (S403a), and the object having P as the head address is set to the area having the address pointed to by free to as the head. Copy (S404a) and increase the value of free to by the size of the copied object (S405a). Then, 1 is added to the value of the age field 56a of this object (S411a).

  After changing the value of the age field 56a of the copy source object (S411, 411a), the processing of Steps 406 and 470 is executed and the copy processing is terminated as in the first embodiment.

  When the root process and the scan process including the copy process (S400a) as described above are finished and the collection of garbage of the young generation is finished, as shown in FIG. 23, the living being stored in the Eden 44 of the young generation area 42a The object is copied to to 46 of the young generation area 42a, and the Eden 44 becomes only a non-living object or a copied object, and can be used as an unused area. The object stored in the to 46 (from 45 after the initialization process) of the young generation area 42a before the garbage collection initialization process is stored in the unused area of the old generation area 43, and the garbage collection initialization process is performed. The previous to 46, in other words, the after 45 after the initialization process is only an object that is not alive or a copied object, and can be used as an unused area.

  By the way, in the scan processing in this embodiment, in steps 301, 302, 303, and 306 of the scan processing of the first embodiment described with reference to FIG. Performs processing with “free” set to “free to”.

  Further, even in the young generation memory content correction process, a process in which the young generation memory content correction process of the first embodiment shown in FIG. The first point is that in the first process, the process changes to the process of substituting the head address of Eden 44 for S in Step 711, and in the determination of Step 712, it is checked whether S is less than the last address of the used area of Eden 44. It is a point to change to processing. The second point is that in the process to be executed next, the process changes to the process of substituting the head address of To46 into S in Step 711. In the judgment of Step 712, is S less than the last address of the area in use of To46? It is a point which changes to the processing which investigates.

  In the above embodiment, the promotion age is always constant, but the promotion age can be made variable depending on the execution status of the system.

[Third embodiment]
A third embodiment will be described with reference to FIG.

  In the present embodiment, as in the first embodiment, when collecting the old generation of garbage, the collection of all generations of garbage is performed without collecting only the garbage of the old generation area.

  For this reason, in the dust collection process of this embodiment, as shown in FIG. 24, the following two points during the dust collection process shown in FIG. 3 in the first embodiment are different. That is, the first point is that after comparing the magnitude relationship between the free capacity OF of the old generation area 43 and the predicted survival amount ES of the young generation area 42 (S4), the young generation is compared with the free capacity OF of the old generation area 43. If the predicted survival amount ES of the area 42 is large, the garbage collection execution unit 21 immediately executes the collection of garbage for all generation areas (S5a). The second point is that when the garbage collection execution unit 21 is collecting garbage in the young generation area 42 (S7), if the free space in the old generation area 43 is not sufficiently secured (S8), it is young. The point is that collection of garbage in the generation area 42 is stopped (S9b), and the garbage collection execution unit 21 immediately executes collection of garbage in all generation areas (S10).

  The dust collection process for all generation areas employs a mark compact system using a Lisp2 algorithm, as in the old generation area 43 of the first embodiment. Therefore, also in the dust collection process for all generation areas in the present embodiment, the mark process, the move destination determination process, the memory content correction process, and the object move process are performed as in the process shown in the flowchart of FIG. However, the present embodiment is slightly different from the first embodiment with respect to the mark process and the movement destination determination process.

  In the mark processing of this embodiment, the reachability fields of all objects reachable from the root among the objects existing in all generation areas are marked.

  In the migration destination determination process according to the present embodiment, first, the migration destination of the object in the old generation area is determined according to the flowchart shown in FIG. 9, and then the migration destination of the object in the young generation area is determined according to the flowchart. . In this case, in step 601 of the flowchart in FIG. 9, the value of the start address of the young generation area is substituted for P, and the substitution process for free is not performed. In step 602, it is determined whether or not the value of P is less than the tail address of the area in use of the young generation area.

  By adding the above-described changes to the method of collecting dust in the old generation area 43 of the first embodiment, it is possible to collect garbage in all generation areas.

  As described above, in this embodiment, if the free space in the old generation area becomes insufficient during the collection of garbage in the young generation area, the collection of garbage in all generation areas is executed although the collection of garbage in the young generation area is stopped. Basically, the same effects as those of the first embodiment can be obtained.

  Here, a modified example of the present embodiment will be described.

  As the object, as in the first embodiment described with reference to FIG. 2, an object having the reachability field 51 and the moved field 52 can be considered. However, these two fields 51 and 52 are one field. It is also conceivable that this single field is both a reachability field and a moved field. Therefore, a method for dealing with such a case will be described below as a modification of the third embodiment.

  Also in this modified example, as in the third embodiment, when the garbage collection of the young generation area 42 is being performed (S7), the free space of the old generation area 43 is not sufficiently secured (S8). ) The garbage collection in the young generation area 42 is stopped (S9b), and the garbage collection execution unit 21 immediately executes the collection of garbage in all generation areas (S10). However, after the young generation garbage collection is stopped (S9b), the young generation garbage collection is performed again. In this young generation garbage collection performed again, if the object having P as the start address has not been moved in step 402 during the copy process shown in FIG. 6, the copy process is terminated with P as a return value. When the collection of garbage for the younger generation is completed again, the reachability field / moved field mark (mark indicating moved) is erased for all objects existing in the younger generation area.

  Further, in the collection of garbage in all generation areas, as in the third embodiment, mark processing, movement destination determination processing, memory content correction processing, and object movement processing are performed. Among these processes, the mark process and the movement destination determination process are the same as in the third embodiment.

  In the memory content modification processing of the young generation in the memory content modification processing, the memory content modification processing of the younger generation in the first embodiment shown in FIG. The process which changed the part is performed. In this young generation memory content correction process, in step 751, the start address of the young generation area is substituted for P in step 751, and in step 752, the value of P is less than the end address of the use area of the young generation area. Judge whether there is. Other processes are the same as those shown in the flowchart of FIG.

  Further, in the destination acquisition process called in each memory content correction process, when steps 734, 735, and 736 in the flowchart shown in FIG. 12 are omitted and it is determined in step 732 that there is no mark in the reachability field. Immediately, the process proceeds to step 737.

[Fourth embodiment]
A fourth embodiment will be described with reference to FIG.

  This embodiment is a modification of the first embodiment. As in the relationship with the modification of the third embodiment, one field in the object in the first embodiment is moved with the reachability field. This is an example in the case of serving as a completed field.

  In this embodiment, an object existing in the old generation area uses the shared field of this object as the reachability field, and an object existing in the young generation area uses the shared field of this object as the moved field. In order to make this distinction, a change is made to the processing when the reachability field is checked depending on whether the object belongs to a young generation area or an old generation area. Furthermore, in the memory content correction process, in the first embodiment, it is distinguished that the destination has been updated by marking the reachability field of the object in the young generation area. By comparing the pointer indicating the completion point of the memory content correction process with the address of the object, it is discriminated whether or not the destination of the object has been updated. Other algorithms are the same as in the first embodiment. Therefore, only differences from the first embodiment will be described below.

  In the young generation memory content correction process shown in FIG. 11, the variable S used in this process is secured as a global variable. This global variable S is used to determine where the memory content correction process has been completed.

  In the destination acquisition process called in each memory content correction process, the process shown in the flowchart of FIG. 25 is performed.

  In the same way as in the first embodiment, the garbage collection execution unit 21 assigns an argument to P (S731) and marks the shared field of the object having P as the start address in this movement destination acquisition process (S730c). An investigation is made as to whether or not there is (S732). When the mark is not attached, unlike the first embodiment, the value of P is immediately set as a return value (S737), and the process ends. That is, in this case, the value given as an argument becomes the return value as it is. If it is marked, it is checked whether the value of P is less than the value of the global variable S described above or whether the value of P is equal to or greater than the start address of the old generation area (S738). When the value of P is smaller than the value of S, it indicates that the mark of the combined field of the object having P as the start address has been moved, and the destination indicated by the destination field of this object is moved by compaction. Indicates the destination. In this case, the destination is the value of the destination field. When P is equal to or greater than the top address of the old generation area, the object having P as the top address belongs to the old generation area, and the value of the destination field of this object becomes the destination of the object.

  If it is determined in step 738 that the value of P is less than the value of the global variable S described above, or the value of P is greater than or equal to the start address of the old generation area, the destination field of this object As a return value (S733), the process is terminated. If it is determined that the value of P is not less than the value of the global variable S and that the value of P is not greater than or equal to the start address of the old generation area, the value of the destination field of this object is the value of this object. Since this indicates the location where the entity exists, this process itself is called with the value of the destination field of this object, that is, the address of the location where the entity exists, as an argument (S735), and the return value from the called process is used as this movement. The return value in the previous acquisition process is used (S736), and the process is terminated.

  As a result of the above changes, even if one field in the object serves both as a reachability field and a moved field, the same processing as in the first embodiment is basically performed except for the processing described above. Can do.

It is explanatory drawing which shows the function structure of the computer of 1st embodiment which concerns on this invention. It is explanatory drawing which shows the data structure of the object of 1st embodiment which concerns on this invention. It is a flowchart of the dust collection process of 1st embodiment which concerns on this invention. FIG. 4 is a flowchart of a young generation garbage collection process in the flowchart of FIG. 3. 5 is a flowchart of scan processing in the flowchart of FIG. 4. It is a flowchart of the copy process during the route process and the scan process of the first embodiment according to the present invention. It is a flowchart of the route process in the flowchart of FIG. It is a flowchart of the garbage collection process of the old generation in the flowchart of FIG. It is a flowchart of the movement destination determination process in the flowchart of FIG. It is a flowchart of the memory content correction process in the flowchart of FIG. It is a flowchart of the memory content correction process of the young generation in the flowchart of FIG. It is a flowchart of the movement destination acquisition process in the flowchart of FIG. It is a flowchart of the memory content correction process of the route in the flowchart of FIG. It is a flowchart of the memory content correction process of the old generation in the flowchart of FIG. It is a flowchart of the object movement process in the flowchart of FIG. It is explanatory drawing for demonstrating judgment of which area | region of a young generation area | region and an old generation area | region which collects garbage in 1st embodiment which concerns on this invention. It is explanatory drawing (the 1) which shows the change of the heap area in the garbage collection execution process in 1st embodiment which concerns on this invention. It is explanatory drawing (the 2) which shows the change of the heap area in the garbage collection execution process in 1st embodiment which concerns on this invention. It is explanatory drawing which shows the function structure of the computer of 2nd embodiment which concerns on this invention. It is explanatory drawing which shows the data structure of the object of 2nd embodiment which concerns on this invention. It is a flowchart of the dust collection process of 2nd embodiment which concerns on this invention. It is a flowchart of the copy process of 2nd embodiment which concerns on this invention. It is explanatory drawing for demonstrating judgment of which area of a young generation area | region and an old generation area | region which collects garbage in 2nd embodiment which concerns on this invention. It is a flowchart of the dust collection process of 3rd embodiment which concerns on this invention. It is a flowchart of the movement destination acquisition process of 4th embodiment which concerns on this invention.

Explanation of symbols

10: Computer, 11: Processor, 12: Virtual machine, 20, 20a: Garbage collection processing unit, 21, 21a: Garbage collection execution unit, 22: Memory monitoring unit, 23: Garbage collection control unit, 24: Calculation of predicted survival amount Part: 25: survival rate prediction unit, 26: survival amount prediction unit, 27: predicted promotion amount calculation unit, 28: promotion rate prediction unit, 29: promotion amount prediction unit, 30: program memory, 31: virtual machine program, 32 : Garbage collection processing (CG) program, 33: execution program, 40: data memory, 41: heap area, 42, 42a: young generation area, 43: old generation area, 50: header, 51: reachability field, 52 : Moved field, 53: destination field, 54: size field, 56, 57, 59: pointer field, 56a: age field, 58: data

Claims (6)

In the garbage collection processing program that divides the memory heap area into multiple generation areas and collects garbage in each generation area,
Garbage collection execution step for collecting garbage from multiple generation areas,
By performing garbage collection for one generation area (hereinafter referred to as a young generation area) of a plurality of generation areas, a living object is selected from one or more objects existing in the young generation area. A movement amount prediction step for predicting the amount of an object to be moved to a generation area one older than a young generation area (hereinafter referred to as an old generation area) from past garbage collection results;
A free capacity measuring step for measuring the free capacity of the old generation area;
If the movement amount of the object in the young generation area predicted in the movement amount prediction step is smaller than the free space in the old generation area measured in the free capacity measurement step, the garbage collection in the young generation area is collected. If the movement amount of the object in the young generation area is greater than or equal to the free capacity of the old generation area, the garbage collection causes the area including the old generation area to be collected in the garbage collection execution step. Control steps;
A garbage collection processing program that causes a computer having the memory to execute. In the garbage collection processing program according to claim 1,
In the garbage collection execution step, when collecting garbage in the young generation area, all the surviving objects are moved to the old generation area from one or more objects existing in the young generation area,
The movement amount prediction step includes:
A usage measuring step for measuring the usage of the young generation area;
A survival rate measuring step of measuring a survival rate, which is a ratio of a survival rate of an object after collecting garbage with respect to an area usage amount of the object before collecting garbage, for each execution of collecting garbage in the young generation region;
A survival rate prediction step of predicting a survival rate at the time of the next garbage collection from the past survival rate measured in the survival rate measurement step;
A survival amount prediction step for predicting a survival amount of an object in the young generation region from the usage amount of the young generation region measured in the usage amount measurement step and the survival rate predicted in the survival amount prediction step; Have
In the garbage collection control step, the survival amount of the object of the young generation region predicted in the survival amount prediction step is compared with the free capacity of the old generation region as the movement amount of the object of the young generation region.
A garbage collection program characterized by that. In the garbage collection processing program according to claim 1,
In the garbage collection execution step, when collecting garbage in the young generation area, only objects that have survived by a predetermined number of garbage collection are selected from one or more objects existing in the young generation area. Move to the old generation area,
The movement amount prediction step includes:
A usage measuring step for measuring the usage of the young generation area;
A survival rate measuring step of measuring a survival rate, which is a ratio of a survival rate of an object after collecting garbage with respect to an area usage amount of the object before collecting garbage, for each execution of collecting garbage in the young generation region;
A survival rate prediction step of predicting a survival rate at the time of the next garbage collection from the past survival rate measured in the survival rate measurement step;
Promotion that measures the promotion rate, which is the ratio of the amount of promotion of the object that moves to the old generation area by collecting the garbage of the young generation area to the survival amount of the object of the young generation area, every time the garbage collection of the young generation area is executed Rate meter side step,
A promotion rate prediction step of predicting a promotion rate in the next garbage collection from the past promotion rate measured in the promotion rate meter side step;
From the usage amount of the young generation area measured in the usage amount measurement step, the survival rate predicted in the survival amount prediction step, and the promotion rate in the next garbage collection predicted in the promotion rate prediction step, A promotion amount prediction step for predicting a promotion amount in the next garbage collection,
In the garbage collection control step, the promotion amount of the object of the young generation area predicted in the promotion amount prediction step is compared with the free capacity of the old generation area as the movement amount of the object of the young generation area.
A garbage collection program characterized by that. In the garbage collection processing program according to any one of claims 1 to 3,
When it is measured during the collection of garbage in the young generation area that the free capacity of the old generation area is not sufficient for collecting garbage in the young generation area, the garbage collection control is performed. In the step, with respect to the garbage collection execution step, execution of garbage collection of the young generation area is interrupted or stopped, and garbage collection of an area including the old generation area is executed.
A garbage collection program characterized by that. In the garbage collection processing method that divides the memory heap area into multiple generation areas and collects garbage in each generation area,
Garbage collection execution process to collect trash from multiple generation areas,
By performing garbage collection for one generation area (hereinafter referred to as a young generation area) of a plurality of generation areas, a living object is selected from one or more objects existing in the young generation area. A movement amount prediction step for predicting the amount of objects to be moved to a generation area one older than the young generation area (hereinafter referred to as an old generation area) from past garbage collection results;
A free capacity measuring step of measuring the free capacity of the old generation area;
If the movement amount of the object in the young generation area predicted in the movement amount prediction step is smaller than the free space in the old generation area measured in the free space grasping step, the garbage collection in the young generation region is collected. If the amount of movement of the object in the young generation area is greater than or equal to the free capacity of the old generation area, the garbage collection causes the area including the old generation area to be collected in the garbage collection execution process. Control process;
A garbage collection processing method comprising: In the garbage collection processing program according to claim 5,
When it is measured during the collection of garbage in the young generation area that the amount of free space in the old generation area is not sufficient for collecting garbage in the young generation area, the garbage collection control is performed. In the process, with respect to the garbage collection execution step, the execution of the garbage collection of the young generation area is interrupted or stopped, and the garbage collection of the area including the old generation area is executed.
A method for collecting and processing garbage.

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