JP5012040B2 - Memory allocation method - Google Patents

Description

  The present invention relates to a memory allocation method, and more particularly to a memory allocation method that ensures that a continuous area is secured in a real address space.

Conventionally, when allocating the real memory space area, the size of the continuous free area is compared with the requested size, and if the free area size is equal to or larger than the requested size, the free area is allocated, and the free area size is the requested size. If it is less, the above process is repeated for the empty area at the higher address, and the process of assigning the empty area found first is performed (for example, see Patent Document 1).
Depending on the program, there is a case where a memory area dynamically secured in the virtual address space must be converted into a real address space and used. Specifically, this corresponds to a stack area / work area when a BIOS call is made, an area used by a peripheral device, and the like. Here, consider a case where memory is dynamically secured from a virtual address space composed of a plurality of pages. Assuming that there is an unusable area in real memory, if you simply use an empty area, addresses may be allocated in a distributed manner, and the area allocated continuously in the virtual address space is the real address. It may not be a continuous area in space. In this case, if this area is used as a real address space, access is made to other than the allocated real address space, and correct memory access cannot be performed.
FIG. 8 shows an example of this. FIG. 8 shows the correspondence between the virtual address space 3 and the real address space 4. For example, the area 31 on the virtual address space 3 is composed of pages V0, V1, V2, and V3. Similarly, the area 41 on the real address space 4 is composed of pages P0, P1, P2,. If it is assumed that the page P2 and the page P6 in the real address space are unusable areas, as one method of simply using the free area, the real address space 4 is added to the page V0 in the virtual address space 3. In the same manner, page P3 is assigned to page V1, page P5 is assigned to page V2, and page P4 is assigned to page V3. At this time, if it is assumed that both the start address and the final address of the area dynamically secured from the virtual address space 3 are within the page V2, this area is also within the page P5 in the real address space. There is no problem because it is continuous even if it is converted to a real address space and used.
However, when the first address of the dynamically allocated area is in page V0 and the last address is in page V1, it corresponds to P1 and P3 on the real address space 4, respectively. It will not be continuous. At this time, if this area is converted into a real address and used, there is a problem that correct memory access cannot be performed. In order to avoid this, it is conceivable to perform address assignment while ensuring that the corresponding areas on the real address space 4 are all continuous.
However, when “unusable areas” exist at intervals smaller than the allocated capacity, an address space that avoids the “unusable areas” must be used. As a result, there is a problem that an area sandwiched between “unusable areas” cannot be used effectively. An example of this is shown in FIG. Here, if it is assumed that the page P2 and the page P6 on the real address space 4 are unusable areas, it will be ensured that the corresponding areas on the real address space 4 are all continuous as described above. Then, pages P7, P8, P9, and P10 that are continuous on the real address space 4 must be associated with the pages V0, V1, V2, and V3, respectively.
This is because the pages P0, P1, P3, P4, and P5 are vacant as areas, but even if they are continuously associated, they overlap with the unusable areas of the page P2 or the page P6. This is because it is not possible to associate with a continuous area on the space 4.
JP 2001-236249 A

As described above, the conventional memory allocation method has a problem that the pages P0, P1, P3, P4, and P5 on the real address space 4 are unused areas and the memory cannot be effectively used.
The present invention has been made in view of such a situation, and even in a computer that cannot have a continuous real address space, an area dynamically secured from the virtual address space is secured as a continuous area in the real address space. It is to be able to guarantee that.

A memory allocation method according to an aspect of the present invention is a memory allocation method for ensuring that a continuous area is secured in a real address space corresponding to a continuous area secured in a virtual address space, the virtual address A search step for searching for a free area that is equal to or larger than the requested size in space; a determination step for determining whether the area crosses a page boundary when an area of the requested size is secured from the free area; and the determination as a result, when it is determined that straddles a page boundary, among the regions, and a temporary area securing step of securing the minimum region size across the page boundary as the temporary area, said temporary reserved in the temporary area securing step Except for the area, again in the area securing step in which the area is secured in the virtual address space and the area securing step. When regions are not cross a page boundary, characterized by comprising a region determination step of determining the area as a reserved area, a release step of releasing the temporary area.
Further, when the size of the remaining area obtained by subtracting the area corresponding to the requested size from the free area is not equal to or smaller than a reference minimum size, the entire free area can be secured as a temporary area.
The temporary area may be an area sandwiching the lowest address of a page on the virtual address space including the highest address of the area and the lowest address of the area.
Further, when the continuous area cannot be secured in the area securing step, the securing may be failed.
A memory allocation device according to an aspect of the present invention is a memory allocation device that ensures that a continuous area is secured in a real address space corresponding to a continuous area secured in a virtual address space, the virtual address A search unit that searches for a free area that is equal to or larger than the requested size in space; a determination unit that determines whether the area crosses a page boundary when the area of the requested size is secured from the free area; and the determination As a result, when it is determined that the page boundary is crossed, a temporary area securing unit that secures, as a temporary area, a minimum size area that crosses the page boundary, and the temporary area secured by the temporary area securing unit. except area, again, the virtual address and the area ensuring means which ensures a region is performed in the space, area page boundary secured by said space securing means When not straddled, characterized in that it comprises a region determining means for determining the area as a reserved area, and a release means for releasing the temporary area.
Further, when the size of the remaining area obtained by subtracting the area corresponding to the requested size from the free area is not equal to or smaller than a reference minimum size, the entire free area can be secured as a temporary area.
The temporary area may be an area sandwiching the lowest address of a page on the virtual address space including the highest address of the area and the lowest address of the area.
In addition, when the area securing unit cannot secure a continuous area, the securing may be failed.
A memory allocation program according to an aspect of the present invention is a memory allocation program in a memory allocation device that ensures that a continuous area is secured in a real address space corresponding to a continuous area secured in a virtual address space. A search step for searching for a free area not less than a requested size in the virtual address space, and a determination step for determining whether or not the area crosses a page boundary when an area of the requested size is secured from the free area when the result of the determination, if it is determined that straddles a page boundary, among the regions, and a temporary area securing step of securing the minimum region size across the page boundary as the temporary area, secured in the temporary area securing step An area reservation step in which an area is reserved again in the virtual address space, except for the temporary area that has been When flop and, an area reserved in the area securing step does not cross a page boundary, executes an area determination step of determining the area as a reserved area, a release step of releasing the temporary area in the memory allocation unit It is characterized by making it.
Further, when the size of the remaining area obtained by subtracting the area corresponding to the requested size from the free area is not equal to or smaller than a reference minimum size, the entire free area can be secured as a temporary area.
The temporary area may be an area sandwiching the lowest address of a page on the virtual address space including the highest address of the area and the lowest address of the area.
Further, when the continuous area cannot be secured in the area securing step, the securing may be failed.

  According to the memory allocation method of the present invention, it is possible to treat an area dynamically secured from the virtual address space as continuous in the real address space. That is, it is possible to ensure that the continuous area dynamically secured in the virtual address space is continuous in the real address space.

  The present invention ensures that the memory area that is dynamically secured in the virtual address space is a continuous area in the real address space, so that the memory space can be used efficiently. It should be noted that the present invention is effective in software that cannot manage pages for each application or a computer that cannot provide continuous real memory space.

  FIG. 1 shows a configuration example of a computer to which the present invention is applied. In FIG. 1, the storage area securing process 2 dynamically secures memory from the virtual address space, and actually secures memory when a request for securing dynamic memory is received from the operating system or application 1. And a function for returning the result to the request source.

  The storage area securing process 2 includes a pre-process 21, a first storage area securing unit 22, and a second storage area securing unit 23. The preprocessing 21 has a function of searching for an empty area in the area to be secured, and also has a function of selecting the first storage area securing means 22 and the second storage area securing means 23 from the result.

  The difference between the first storage area securing means 22 and the second storage area securing means 23 is that the processing is determined due to the relationship between the capacity of the searched free area and the capacity of the actually reserved area. When the first storage area securing unit 22 is selected, first, the memory area address when the requested capacity is collected from the free area detected in the preprocessing 21 is calculated. If the start and end addresses of this calculated memory area do not straddle the page boundary managing the virtual address space, this dynamic memory allocation can guarantee that the physical address space is also a continuous area. Proceeding to the first normal securing means 221, the memory is actually secured.

  On the other hand, if the calculated first and last addresses of the memory area cross the page boundary, the dynamic memory reservation cannot guarantee that the physical address space is a continuous area. Proceed to The first avoidance securing means 222 arranges a temporary area in an area straddling the page boundary, recursively advances to the storage area securing process 2 and tries to secure again.

  In re-allocation, when the first normal allocation unit 221 or the second normal allocation unit 232 can allocate an area that is continuous in the real address space, the storage area allocation process 2 is called recursively. It returns as a successful reservation together with the start address that can be secured in the avoidance securing means 222. The avoidance securing unit 222 that has returned from the recursive execution releases the temporary area that has been secured first, and returns it to the address requester of the secured area in the re-allocation.

  Note that the re-allocation processing is attempted not only for the second time but also until it can be allocated, but is repeated at most (number of pages-1) times. Also, the provisional area must be arranged in the area that crosses the page boundary in order to avoid re-allocation in the area when re-allocation is attempted.

  On the other hand, when the second storage area securing means 23 is selected, first, the free area detected in the preprocessing 21 is secured as an area to be used. If this area does not straddle the page boundary that manages the virtual address space, the dynamic memory allocation can be guaranteed to be a continuous area in the physical address space. Confirm as an area.

  On the other hand, if the beginning and end addresses of this memory area straddle the page boundary, the dynamic memory allocation cannot guarantee that the physical address space is a continuous area, so the process proceeds to the second avoidance securing means 232. . In the second avoidance securing means 232, an area straddling the page boundary is set as a temporary area, and the process proceeds recursively to the storage area securing process 2 to try to secure again.

  Similar to the first avoidance securing means 222, when the first normal securing means 221 or the second normal securing means 232 can secure a continuous area in the real address space in the re-reserving, recursively. It returns as a successful reservation together with the head address that can be secured in the second avoidance securing means 232 that called the storage area securing process 2.

  The avoidance securing unit 232 that has returned from the recursive execution releases the provisional area secured first, and returns it to the address requester of the secured area in the re-allocation.

  With the above operation, it is possible to avoid securing dynamic memory across page boundaries, and to ensure continuity in the real address space.

  Referring to FIG. 1, the present embodiment includes an operating system or application 1 and a storage area securing process 2. There is no limitation on the type of the operating system or operating system of the application 1, and the operating system, for example, a dynamic memory allocation request such as a task area, a semaphore area, or a timer area from the work area managed by the operating system, Implement a dynamic memory allocation request from the heap area. Similarly, a dynamic memory allocation request from the heap area, for example, a malloc () function call in C language is executed from the application.

  The storage area securing process 2 includes pre-processing 21, first storage area securing means 22, and second storage area securing means 23. In the storage area securing process 2, a dynamic memory securing request from the operating system or the application 1 is received, the dynamic memory securing from the designated area is executed, and if the securing succeeds, the securing is performed A function of returning the head address to the operating system or application 1. In addition, it has a function of notifying the securing failure when securing fails.

  The pre-processing 21 has a function of searching for a free area satisfying the requested capacity from the designated areas and determining whether to execute the first storage area securing means 22 or the second storage area securing means 23. Yes. Here, the selection criterion of the first storage area securing unit 22 or the second storage area securing unit 23 is that the remaining free area responds to a further securing request even if the requested capacity is secured from the searched free area. If the answer is yes, the first storage area securing means 22 is used, and if not, the second storage area securing means 23 is used. The first storage area securing unit 22 includes a first normal securing unit 221 and a first avoidance securing unit 222, and also has a function of calculating an address of an area scheduled to be secured.

  The first normal securing means 221 has a function to execute the dynamic memory securing of the requested capacity from the detected area when the area to be secured this time is an area that does not cross the page boundary. A function of notifying the address of the obtained dynamic memory area to the first storage area securing means 22.

  The first avoidance securing means 222, when the area to be secured is an area that crosses the page boundary, a function that arranges a temporary area with the minimum capacity across the area and a function that recursively calls the storage area securing process 2; The function of releasing the temporary area when the storage area securing process 2 is finished, and the address of the dynamic memory area obtained by executing recursively, or the first storage area securing means that the securing has failed 22 is notified.

  The second storage area securing means 23 is different in function from the first storage area securing means 22 because the capacity of the searched free area is different. The second storage area securing unit 23 also includes a second normal securing unit 231 and a second avoidance securing unit 232.

  First, the second storage area securing unit 23 secures the entire searched free area as a requested size area. Thereafter, when the secured area is an area that does not cross the page boundary, the second normal securing means 231 is selected, and when the secured area is the straddling area, the second avoidance securing means 232 is selected. Is provided.

  The second normal securing means 231 has a function of determining the secured area as dynamic memory securing of the requested capacity when the secured area is an area that does not cross the page boundary, and the obtained dynamic memory area It has a function of notifying the address to the second storage area securing means 23.

  The second avoidance securing means 232, when the secured area is an area that crosses the page boundary, a function that makes the area a temporary area, a function that recursively calls the storage area securing process 2, and a storage area securing process Notifies the second storage area securing means 23 of the function of releasing the temporary area when the processing of 2 is completed and the address of the dynamic memory area obtained by recursively executing or the allocation failure It has a function.

  Next, the operation of the embodiment of the present invention will be described in detail with reference to the flowcharts of FIGS. 1 to 4 and FIG. FIG. 2 shows that continuous areas (pages P7, P8, P9, P10) can be secured in the real address space corresponding to the continuous areas (pages V0, V1, V2, V3) secured in the virtual address space. Yes, but the area (pages P3, P4, P5) sandwiched between the “unusable areas (pages P2, P6)” is wasted, and there are unused areas (pages P3, P4, P5). Shows a state in which a continuous area corresponding to continuous areas (pages V0, V1, V2, and V3) secured in the real address space and the virtual address space cannot be secured.

  FIG. 3 schematically shows the problem to be solved by the present invention. Due to the dynamic memory allocation, the page V0 in the area allocated in the virtual address space corresponds to the page P1 in the real address space, the page V1 corresponds to the page P3, the page V2 corresponds to the page P5, and the page V3. Corresponds to page P4, area # 1 in page V3 in the virtual address space is allocated in page P4 in the real address space. In this case, since the area # 1 does not straddle pages in the virtual address space, it is guaranteed that the area # 1 is a continuous area even in the real address space. On the other hand, since the area # 2 secured in the virtual address space straddles the pages V0 and V1 in the virtual address space, it is not guaranteed to be a continuous area in the real address space. In this example, It is divided and assigned to pages P1 and P3 across the “unusable area (page P2)”. That is, it is divided on the real address space and does not become a continuous area.

  FIG. 4 is a schematic diagram showing a method for solving the problem shown in FIG. FIG. 4A shows a state before a new area is secured in the virtual address space. FIG. 4B shows a state in which an area straddling pages V1 and V2 is about to be secured as a secured area in the virtual address space. FIG. 4C shows a state where a temporary area is secured in an area straddling pages V1 and V2 in the virtual address space. However, the temporary area is an area having the minimum size across the page boundary. In this example, the area in use occupies the middle of pages V0 to V1, and the temporary area is the area from the next address on the upper side of the highest address of the area in use to the lowest address of page V2. It becomes.

  FIG. 4D shows a state in which the required size securing area is acquired again. The area secured as the temporary area is not subject to securing the area of the required size. For this reason, in this example, the secured area is secured from the next address on the upper side of the temporary area and is contained in the page V2. FIG. 4E shows a state in which the temporary area is released after the reserved area has been acquired. Since the secured area secured as a continuous area in the virtual address space does not straddle a page, it is guaranteed that the secured area is also a continuous area in the real address space.

  The operation of the present embodiment will be described below with reference to the flowchart of FIG. First, a dynamic memory allocation request is issued from the operating system or application 1 (step S1). When the storage area securing process 2 receives a memory securing request from the operating system or the application 1, the pre-process 21 searches for a free area in the secured area in the virtual address space (steps S2, S3, and S9). . In general, free space allocation methods include a first match (First-Fit), a best match (Best-Fit), and a worst match (Worst-Fit). (Best-Fit) and worst match (Worst-Fit) will be described later.

  Since the search is performed with the head match, when an area larger than the requested capacity is found among the searched free areas, it is confirmed whether or not the capacity is equal to the requested capacity (step S4). If the last area is searched and not found, securing fails (step S10).

  In step S4, it is confirmed whether or not it is equal to the requested capacity. Strictly speaking, it is confirmed whether or not the remaining capacity obtained by subtracting the current requested capacity from the free area is equal to or larger than the minimum capacity including the management block. ing. That is, it is checked whether or not the remaining capacity after the subtraction has a minimum capacity that can secure an area according to another request. This is because an area where the minimum capacity does not remain cannot be left as an empty area.

  If it is not equal to the requested capacity, that is, if the minimum capacity remains even if the current requested capacity is subtracted from the searched free area, the process from the pre-processing 21 to the first storage area securing means 22 is performed. move on. The first storage area securing means 22 calculates the memory area address when the required capacity is collected from the searched free area.

  It is confirmed whether or not the calculated first and last addresses of the memory area cross the page boundary (step S51). If not straddling, since it can be ensured that this dynamic memory allocation is a continuous area in the physical address space, the process proceeds to the first normal allocation means 221 and actual memory allocation is performed (step S82). Finally, the start address of the secured dynamic memory area is returned to the memory request source (step S102).

  If it is determined in step S51 that the page boundary is crossed, the dynamic memory allocation cannot be guaranteed to be a continuous area in the physical address space, and the process proceeds to the first avoidance securing unit 222. The first avoidance securing unit 222 first calculates the minimum size among the sizes straddling the page boundary. In other words, the size (minimum size) of the minimum area across the page boundary is calculated. Then, a temporary area is temporarily secured with the minimum size (step S61). This is to avoid trying to secure the same area when attempting to secure again.

  After securing the temporary area, the present algorithm is recursively executed with the same required capacity (step S81). Recursive execution starts from step S2. This means that an imaginary area is arranged in the area where the first securing is attempted, and a request for securing the same capacity is made in a state where the same state is avoided again. If the memory can be secured in the above-described step S82 or later-described step S84 by the recursive securing request, the dynamic memory securing of the requested capacity can be secured in the second retry.

  Conversely, even if the second recursive reservation request fails, re-reservation is attempted as much as possible by executing this algorithm again recursively. Since the retry is performed every time the region crosses the page boundary, there may be a maximum of (number of pages-1) retries (the number of pages is the maximum value when counting the first allocation request). .

  Of course, if there is no other free area that can be secured during the retry, a notification of failure to secure is returned, but in any case, the maximum number of retries is (number of pages minus 1). Become. When returning from the recursive securing process, the process returns to the first avoidance securing unit 222 to release the provisional area secured previously (step S91). Finally, the result obtained from the recursive execution is returned (step S101).

  On the other hand, if it is determined in step S4 that it is equal to the requested capacity, that is, the capacity (size) of the remaining area obtained by subtracting the area for the current requested capacity (for the requested size) from the free area is the management block. If there is no more than the minimum capacity (minimum standard size) to be included, the process proceeds from the pre-processing 21 to the second storage area securing means 23.

  The second storage area securing means 23 secures the searched free area as an area to be used (step S53). Next, it is confirmed whether or not the start and end addresses of this reserved area cross the page boundary (step S63).

  If it does not straddle, this dynamic memory allocation can guarantee that the physical address space is also a continuous area, so the process proceeds to the second normal allocation means 231 to determine the area as an area satisfying the required capacity (step S84). Then, the start address of the dynamic memory area is returned to the memory request source (step S104).

  If it is determined in step S63 that the page boundary is crossed, the dynamic memory allocation cannot be guaranteed to be a continuous area in the physical address space, and the process proceeds to the second avoidance securing unit 232. The second avoidance ensuring unit 232 determines the area as a temporary area (step S73). This is also for avoiding securing the same area when securing is attempted again, as in step S61.

  After securing the temporary area, the present algorithm is recursively executed with the same required capacity (step S83). Then, when returning from the recursive execution, the temporary area is released (step S93). Finally, the result of the recursive execution is returned to the request source and the process ends (step S103). The above is the operation of the present embodiment.

  According to the present embodiment, the following effects can be obtained. The first effect is that the memory can be effectively used. The reason is that even in software that cannot manage pages for each application or a computer that does not have a continuous real address space, an area dynamically secured from the virtual address space can be treated as continuous in the real address space.

Next, another embodiment of the present invention will be described. There are generally the following three methods for allocating free areas.
(1) First match (First-Fit): assigned to the first executable area in the free area (2) Best match (Best-Fit): assigned to the smallest of the executable areas in the free area (3 ) Worst-Fit: assigned to the largest of the executable areas in the free area

  In FIG. 5 described above, an example of “first match” is illustrated, but the concept of the present invention can be applied to all of the above three allocation methods. In either case, there is no difference in the essence of the present invention, but FIG. 6 shows a flowchart of “best match”. As in the case of “first match” shown in FIG. 5, a dynamic memory allocation request is issued from the operating system or application 1 (step S1).

  When the storage area securing process 2 receives a memory securing request from the operating system or the application 1, the pre-process 21 searches for a free area in the secured area (steps A2 and A9).

  In order to search for “best match”, all free areas are searched, and the smallest area that satisfies the required capacity is detected (step A3). If a region meeting this condition is found, it is confirmed whether or not the capacity is equal to the required capacity (step S4). Since the subsequent processing is the same as that in the case of “first match”, the description thereof is omitted. It should be noted that if a region that satisfies the condition is not found, securing fails (step S10).

  FIG. 7 shows a flowchart of “worst match”. As in the case of “first match” shown in FIG. 5, a dynamic memory allocation request is issued from the operating system or application 1 (step S1).

  When the storage area securing process 2 receives a memory securing request from the operating system or the application 1, the pre-process 21 searches for a free area in the secured area (steps B2 and B9).

  In order to search for “best match”, all the empty areas are searched, and the largest area among them is detected and the largest area is detected (step B3). If a region meeting this condition is found, it is confirmed whether or not the capacity is equal to the required capacity (step S4). Since the subsequent processing is the same as that in the case of “first match”, the description thereof is omitted. It should be noted that if a region that satisfies the condition is not found, securing fails (step S10).

  It should be noted that the configuration and operation of the above-described embodiment are examples, and it goes without saying that they can be changed as appropriate without departing from the spirit of the present invention.

  The present invention can be applied to all kinds of computers from small to large scales, but is particularly effective in a computer in which software that cannot manage pages for each application is installed or a computer that cannot obtain a continuous real memory space. In addition, since the memory can be used effectively, it is effective in the field of embedded systems where a wide range of products have been released recently.

It is a block diagram which shows the structural example of the computer to which this invention is applied. It is a figure which shows the area | region ensured on the real address space corresponding to the continuous area ensured in the virtual address space. It is a figure which shows typically the subject which this invention should solve. It is a schematic diagram which shows the method of solving the subject shown in FIG. It is a flowchart for demonstrating operation | movement of this Embodiment. It is a flowchart which shows the example of the operation | movement by "best match." It is a flowchart which shows the example of the operation | movement by "worst coincidence." It is a figure which shows the example of matching with virtual address space and real address space It is a figure which shows the example which cannot use effectively the area | region pinched | interposed into the "unusable area".

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Operating system or application 2 Storage area reservation process 3 Virtual address space 4 Real address space 21 Pre-processing 22 First storage area reservation means 23 Second storage area reservation means 31 Area on virtual address space 41 On real address space Area 221 First normal securing means 222 First avoidance securing means 231 Second normal securing means 232 Second avoidance securing means

Claims (12)

A memory allocation method for ensuring that a continuous area is secured in a real address space corresponding to a continuous area secured in a virtual address space,
A search step of searching for a free area of a requested size or more on the virtual address space;
A determination step of determining whether or not the area crosses a page boundary when an area of the required size is secured from the free area; and
A result of the determination, if it is determined that straddles a page boundary, among the regions, and a temporary area securing step of securing the area of the smallest size across the page boundary as the temporary area,
An area securing step in which an area is secured on the virtual address space again, except for the provisional area secured in the provisional area securing step;
When the area secured in the area securing step does not cross a page boundary, an area confirming step for confirming the area as a secured area;
A memory allocation method comprising: a releasing step of releasing the temporary area. The entire free area is secured as a temporary area when the size of the remaining area obtained by subtracting the area for the requested size from the free area is not equal to or smaller than a reference minimum size. The memory allocation method described. The memory allocation according to claim 1, wherein the temporary area is an area that sandwiches the lowest address of a page on the virtual address space including the highest address of the area and the lowest address of the area. Method. The memory allocation method according to any one of claims 1 to 3, wherein when the continuous area cannot be secured in the area securing step, securing fails. A memory allocation device that ensures that a continuous area is secured on a real address space in correspondence with a continuous area secured on a virtual address space,
Search means for searching for a free area of the requested size or more in the virtual address space;
Determination means for determining whether or not the area crosses a page boundary when the area of the required size is secured from the free area;
A result of the determination, if it is determined that straddles a page boundary, among the regions, and a temporary area securing means to secure the area of the smallest size across the page boundary as the temporary area,
Excluding the temporary area secured by the temporary area securing means, an area securing means for securing the area again on the virtual address space;
When the area secured by the area securing means does not cross a page boundary, area confirming means for confirming the area as a secured area;
A memory allocation device comprising: release means for releasing the temporary area. The entire free area is secured as a temporary area when the size of the remaining area obtained by subtracting the area for the requested size from the free area is not equal to or smaller than a reference minimum size. The memory allocation device described. The memory allocation according to claim 5, wherein the temporary area is an area that sandwiches the lowest address of a page on the virtual address space including the highest address of the area and the lowest address of the area. apparatus. The memory allocation device according to any one of claims 5 to 7, wherein when the area securing unit cannot secure a continuous area, the securing is failed. A memory allocation program in a memory allocation device for ensuring that a continuous area is secured on a real address space corresponding to a continuous area secured on a virtual address space,
A search step of searching for a free area of a requested size or more on the virtual address space;
A determination step of determining whether or not the area crosses a page boundary when an area of the required size is secured from the free area; and
A result of the determination, if it is determined that straddles a page boundary, among the regions, and a temporary area securing step of securing the area of the smallest size across the page boundary as the temporary area,
An area securing step in which an area is secured on the virtual address space again, except for the provisional area secured in the provisional area securing step;
When the area secured in the area securing step does not cross a page boundary, an area confirming step for confirming the area as a secured area;
A memory allocation program that causes the memory allocation device to execute a release step of releasing the temporary area. The entire free area is secured as a temporary area when the size of the remaining area obtained by subtracting the area for the requested size from the free area is not equal to or smaller than a reference minimum size. The memory allocation program described. The memory allocation according to claim 9, wherein the temporary area is an area that sandwiches a lowest address of a page on the virtual address space including a highest address of the area and a lowest address of the area. program. The memory allocation program according to any one of claims 9 to 11, wherein when the continuous area cannot be secured in the area securing step, the securing is failed.

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