JP2008033838A - Memory management device and memory management method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a memory management device and a memory management method capable of realizing efficient memory management in a fixed-length block system. <P>SOLUTION: A domain securing part 11 is provided for securing domains partitioned into a plurality of first fixed-length blocks in an unsecured domain in a memory 2, and a free domain determining part 12 is provided for determining whether or not there is a free domain of a requested size or more on the secured domain when there is an allocation request of the memory 2, and a request including information of size to be allotted is received from the outside. In the domain securing part 11, if there is no free domain of a requested size or more on the secured domain, one or more first fixed-length blocks are newly secured in continuance with the secured domain in the unsecured domain to secure a free domain of the requested size or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a memory management device and a memory management method applied to an embedded system.

  A built-in system such as a mobile phone includes a CPU having a low processing capacity and a small-capacity memory as compared with a personal computer (PC). In the embedded system, when a memory is necessary, a “memory pool function” that secures a necessary area in units of memory blocks and releases it when it is no longer needed is implemented as a function of the operation system (OS).

  The memory pool function includes a fixed-length block method and a variable-length block method depending on the size of usable memory blocks. The “fixed-length block method” is a method in which a plurality of fixed-length memory blocks are prepared in advance and the memory is managed in units of fixed-length memory blocks. In the fixed-length block method, it is possible to secure the memory by the number of memory blocks prepared first, but the memory utilization efficiency is likely to be reduced by securing the memory even though it is not actually used.

  The “variable length block method” is a method for dynamically securing memory blocks in units of variable length memory blocks. Therefore, it is advantageous from the viewpoint of memory utilization efficiency, but by repeating securing and releasing in units of memory blocks of different sizes, the memory block in use and the free space appear discontinuously, and the memory block in use Fragmentation (fragmentation) in which a small vacant area appears between them is likely to occur.

As a technique for suppressing the occurrence of fragmentation in the variable-length block method, comprising a reference size storage means for storing a reference size used for determining whether the search direction of the free area is ascending order or descending order of the memory address, If the data size is greater than or equal to the reference size, the search direction is descending, and if the data size is less than the reference size, the search direction is ascending, and the free space that was first explored as having a size greater than or equal to the data size is selected. A method for allocating memory to data has been proposed (see Patent Document 1).
JP 2005-157714 A

  When the variable-length block method is applied to an embedded system, the mounting burden is large and the real-time property is easily lost. For this reason, a real-time OS used in an embedded system may not support the variable-length block method but may support only the fixed-length block method. In such a case, the fixed length block method is used. However, as described above, in the fixed-length block method, a memory is secured even though it is not actually used. In the fixed-length block method, fragmentation tends to occur when the memory block size is reduced. Further, in the fixed-length block method, if the size of the memory block is increased, one block is used for a memory request of a small size. Therefore, if the fixed-length block method is used, efficient memory management becomes difficult.

  In view of the above problems, an object of the present invention is to provide a memory management device and a memory management method capable of realizing efficient memory management in a fixed-length block method.

  In order to achieve the above object, a first feature of the present invention is that an area securing unit for securing an area divided into a plurality of first fixed-length blocks in an unallocated area in the memory, and a memory allocation request A free area determination unit that determines whether or not a free area larger than the requested size exists in the reserved area when a request including information on a size to be allocated is received from the outside, The securing unit secures one or more new first fixed-length blocks in succession to the secured area in the unsecured area when there is no free area of the requested size or more in the secured area. Thus, the gist of the present invention is a memory management device that secures a free area of a requested size or more.

  According to this feature, when there is no free area of the requested size or more in the reserved area, the area securing unit newly fixes the first fixed area in the unsecured area continuously to the secured area. Since one or more long blocks are secured and a free space of a requested size or more is secured, the memory can be used efficiently and errors due to fragmentation can be suppressed.

  The second feature is that in the memory management device according to the first feature, when the newly secured area of the first fixed-length block is released, an area release unit that sets the released area as an unsecured area is further provided. The gist is to provide.

  According to this feature, when the newly secured area of the first fixed-length block is released, the released area is set as an unsecured area, so that the memory can be used efficiently.

  A third feature is that, in the memory management device according to the first or second feature, the area securing unit secures an area further divided into a plurality of second fixed-length blocks in the unsecured area. The gist.

  According to this feature, the area securing unit secures two memory areas including fixed-length blocks of different sizes that secure an area divided into a plurality of second fixed-length blocks in the unsecured area. The two memory areas can be used properly, and the memory can be used efficiently.

  A fourth feature of the present invention is a step of securing an area divided into a plurality of first fixed-length blocks in an unallocated area in the memory, and a memory allocation request, which includes information on the allocation size. If the request is received from the outside, a step of determining whether or not a free area larger than the requested size exists in the reserved area, and a free area larger than the requested size exists in the reserved area. If not, a memory management method including the step of securing one or more first fixed-length blocks in the unallocated area in succession to the secured area and securing a free area of a requested size or more. It is a summary.

  According to the present invention, it is possible to provide a memory management device and a memory management method capable of realizing efficient memory management in the fixed-length block method.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(Memory management device)
Prior to the description of the memory management device according to the embodiment of the present invention, the hardware configuration of an embedded system to which the memory management device is applied will be briefly described with reference to FIG. In the example of FIG. 1A, an outline of a mobile phone system is shown. The system includes a CPU 10, a memory 2, a ROM 5, and a communication device 6. The ROM 5 functions as a program storage device that stores a program executed by the CPU 10. The memory 2 mainly functions as a temporary data memory or the like that temporarily stores data or the like used during program execution processing in the CPU 10 or is used as a work area. The programs stored in the ROM 5 include an OS (real-time OS) that controls the CPU 10 in addition to various applications. This OS has a memory management function for managing the memory 2 using the above-described fixed-length block method. The communication device 6 executes various communication processes.

  Next, FIG. 1B shows an example of the functional configuration of the system shown in FIG. The CPU 10 in FIG. 1A executes the functions of the processing device 3 and the memory management device 1 in FIG. The processing device 3 includes a plurality of modules 31, 32,... Corresponding to each application. The plurality of modules 31, 32,... Share the memory 2 for use.

  The memory management device 1 includes an area securing unit 11, a free area determination unit 12, a free area allocation unit 13, and an area release unit 14. The area securing unit 11 secures a memory area divided into a plurality of fixed-length blocks with respect to an unsecured area in the memory 2. As a result, the memory 2 has two memory areas, namely, a memory area where the modules 31, 32,... Can be used (hereinafter referred to as “allocated areas”) and an unallocated area where the modules 31, 32,. Divided into areas.

  When the memory area request for allocation of the memory 2 is received from the modules 31, 32,..., The free area determination unit 12 determines whether or not there is a free area larger than the requested size in the secured area. judge. The free area allocation unit 13 allocates a free area to a memory request when a free area having a size larger than the requested size exists in the reserved area.

  In addition, when there is no free area of the requested size or more in the secured area, the area securing unit 11 adds at least one fixed length block to the secured area and uses it for the unsecured area. Extend possible memory space. In other words, the area securing unit 11 secures one or more new fixed-length blocks in succession to the secured area in the unsecured area. At this time, the area securing unit 11 secures a free area that is equal to or larger than the requested size. In the following, the size at which the modules 31, 32,... Request memory allocation is referred to as “requested size”. The expanded area (that is, a newly usable area) is referred to as an “extended memory area”.

  When the extended memory area is released, the area releasing unit 14 sets the released extended memory area as an unsecured area again.

  Details of each function of the area securing unit 11, the free area determination unit 12, the free area allocation unit 13, and the area release unit 14 will be described below.

  First, details of the area securing unit 11 will be described with reference to FIG. In the example of the memory arrangement in FIG. 2, the area securing unit 11 is an area (hereinafter referred to as “first secured area”) composed of fixed-length blocks (hereinafter referred to as “small capacity blocks”) having a predetermined size. An area (hereinafter referred to as a “second reserved area”) composed of a fixed-length block (hereinafter referred to as “large capacity block”) having a size larger than that of the small capacity block is secured.

  The first reserved area is arranged from the top address of the memory 2 to the last address. The second reserved area is arranged from the last address of the memory 2 to the first address.

  The area securing unit 11 prepares the minimum number of fixed-length blocks at the time of securing the secured area for the first time. Therefore, an unsecured area remains between the first secured area and the second secured area.

  Next, details of the free space determination unit 12 and the free space allocation unit 13 will be described with reference to FIG.

  The free area determination unit 12 determines which of the first reserved area and the second reserved area should be allocated according to the request size of the received memory request. As an example, the free space determination unit 12 compares the request size with a threshold value, and determines that the allocation is made to the first secured region if the size is equal to or smaller than the threshold value. On the other hand, when the threshold value is exceeded, the free space determination unit 12 determines to allocate to the second secured region.

  When it is determined that the first reserved area is to be allocated, the free area determination unit 12 searches for a free area from the top address to the last address of the memory 2. On the other hand, when it is determined that the allocation is made to the second secured area, the free area determination unit 12 searches for a free area from the last address of the memory 2 toward the first address.

  In the case of allocating to the first reserved area, as shown in FIG. 3A, when there is a free area composed of continuous small capacity blocks that satisfy the requested size, the free area allocation unit 13 Make an assignment.

  When allocating to the first reserved area, as shown in FIG. 3B, if there is no free area consisting of continuous small-capacity blocks satisfying the requested size, the area ensuring unit 11 By adding at least one small-capacity block (here, three) to the reserved area, the usable memory area is expanded toward the unsecured area. The area securing unit 11 determines the number of blocks to be added according to the requested size. As a result, an extended memory area is created, and the free area allocating unit 13 assigns the created extended memory area.

  Next, details of the area release unit 14 will be described with reference to FIG. As shown in FIG. 4A, the area releasing unit 14 releases a free area as it is when an area other than the extended memory area is released. On the other hand, as shown in FIG. 4B, the area releasing unit 14 sets the released area as an unallocated area when the extended memory area is released.

  Thus, when the extended memory area is released, the size of the first first reserved area can be maintained by setting the released extended memory area as an unsecured area, and the memory can be used efficiently.

(Memory management method)
Next, an overview of the memory management method according to the embodiment of the present invention will be described with reference to the flowchart shown in FIG.

  In step S11, the area securing unit 11 creates first and second secured areas as shown in FIG.

  In step S12, the area securing unit 11, the free area determining unit 12, and the free area allocating unit 13 perform the allocation process of the memory 2 in response to a memory request from the modules 31, 32,.

  In step S13, the area release unit 14 performs a release process of the memory 2 in response to a release request from the modules 31, 32,.

  Next, the details of step S12 in FIG. 5 will be described with reference to the flowchart shown in FIG.

  In step S101, when a memory request is received from the modules 31, 32,..., The process proceeds to step S102.

  In step S102, the free area determination unit 12 determines which of the first reserved area and the second reserved area is to be allocated according to the request size of the memory request received in step S101. When allocating to the 1st reserved area | region, it transfers to step S104. When allocating to the 2nd reserved area | region, it transfers to step S103.

  In step S <b> 104, the free space determination unit 12 searches for free space from the first address to the last address of the memory 2.

  In step S105, the free space determination unit 12 determines whether or not a free space larger than the requested size exists in the first reserved region. If a free area larger than the requested size exists in the first reserved area, the process proceeds to step S107. If there is no free area larger than the requested size in the first reserved area, the process proceeds to step S108.

  In step S106, the area securing unit 11 secures one or more new small-capacity blocks in succession to the first secured area in the unsecured area, and secures a free area that is larger than the requested size.

  In step S107, the free area allocation unit 13 allocates a free area to the memory request received in step S101.

  On the other hand, in step S <b> 103, the free area determination unit 12 searches for a free area from the last address of the memory 2 toward the start address.

  In step S109, the free space determination unit 12 determines whether a free space larger than the requested size exists in the second secured region. If a free area larger than the requested size exists in the second reserved area, the process proceeds to step S110. If there is no free area larger than the requested size in the second reserved area, the process proceeds to step S111.

  In step S110, the area securing unit 11 secures one or more new large-capacity blocks in succession to the second secured area in the unsecured area, and secures a free area that is equal to or larger than the requested size.

  In step S111, the free area allocation unit 13 allocates a free area to the memory request received in step S101.

  Next, the details of step S13 in FIG. 5 will be described with reference to the flowchart shown in FIG.

  In step S201, the area release unit 14 receives a release request from the modules 31, 32,.

  In step S202, the area releasing unit 14 determines whether or not the extended memory area has been released. When the extended memory area is released, the process proceeds to step S203. When the reserved area other than the extended memory area is released, the process proceeds to step S204.

  In step S203, the area releasing unit 14 sets the released area as an unsecured area.

  In step S204, the area releasing unit 14 sets the released area as a free area.

  As described above in detail, according to the embodiment of the present invention, when there is no free area larger than the requested size in the reserved area, a new area is newly added in the reserved area. Secure one or more fixed-length blocks to secure a free space that is larger than the requested size, so that you can secure a continuous free space to efficiently use the memory and suppress errors caused by fragmentation. Can do.

(Other embodiments)
As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the embodiment described above, an example has been described in which the area securing unit 11 creates two secured areas, a first secured area composed of small capacity blocks and a second secured area composed of large capacity blocks. . However, the area securing unit 11 may create only one secured area without creating two secured areas.

  Alternatively, the area securing unit 11 may further create a third secured area composed of fixed-length blocks having different sizes from the small capacity block and the large capacity block. By preparing three patterns of fixed-length block sizes, more efficient memory management can be realized.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

It is a block diagram which shows the structural example of the memory management system which concerns on embodiment of this invention. It is a schematic diagram for demonstrating the function of the area | region securing part which concerns on embodiment of this invention. It is a schematic diagram for demonstrating the function of the area reservation part which concerns on embodiment of this invention, and an empty area allocation part. It is a schematic diagram for demonstrating the function of the area | region release part which concerns on embodiment of this invention. It is a flowchart which shows the outline | summary of the memory management method which concerns on embodiment of this invention. It is a flowchart which shows the memory allocation processing flow which concerns on embodiment of this invention. It is a flowchart which shows the memory release process flow which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Memory management apparatus 2 ... Memory 3 ... Processing apparatus 5 ... ROM
6 ... Communication device 10 ... CPU
DESCRIPTION OF SYMBOLS 11 ... Area reservation part 12 ... Empty area determination part 13 ... Empty area allocation part 14 ... Area release part 31, 32, ... Module

Claims (4)

An area securing unit for securing an area divided into a plurality of first fixed-length blocks in an unallocated area in the memory;
A free space determination unit that determines whether or not a free space larger than the requested size exists in the secured region when a request including allocation size information is received from the outside as the memory allocation request And
When there is no free area of the requested size or more in the reserved area, the area securing unit newly adds the first fixed-length block continuously to the secured area in the unsecured area. One or more memory management devices are provided, and a free space of the requested size or more is secured.   2. The memory management device according to claim 1, further comprising an area releasing unit that sets the released area as an unsecured area when the area of the newly secured first fixed-length block is released.   The memory management device according to claim 1, wherein the area securing unit reserves an area further divided into a plurality of second fixed-length blocks in the unsecured area. Securing an area divided into a plurality of first fixed-length blocks in an unsecured area in the memory;
Determining whether or not a free area larger than the requested size exists in the secured area when the memory allocation request is received from the outside and includes a request including size information to be allocated;
If a free area of the requested size or larger does not exist in the reserved area, one or more new first fixed-length blocks are continuously allocated in the unsecured area in succession to the reserved area. And a memory management method, comprising the step of securing a free area of the requested size or more.

Images